Amaca Pty Ltd v Ellis & Ors

[2009] HCATrans 297

[2009] HCATrans 297

IN THE HIGH COURT OF AUSTRALIA

Office of the Registry
  Perth  No P13 of 2009

B e t w e e n -

AMACA PTY LTD (ACN 000 035 512)

Appellant

and

TERESA ELLIS AS EXECUTOR OF THE ESTATE OF PAUL STEVEN COTTON (DEC)

First Respondent

THE STATE OF SOUTH AUSTRALIA

Second Respondent

MILLENNIUM INORGANIC CHEMICALS LTD (ACN 008 683 627)

Third Respondent

Office of the Registry
  Perth  No P14 of 2009

B e t w e e n -

THE STATE OF SOUTH AUSTRALIA

Appellant

and

TERESA ELLIS AS EXECUTOR OF THE ESTATE OF PAUL STEVEN COTTON (DEC)

First Respondent

AMACA PTY LTD (ACN 000 035 512)

Second Respondent

MILLENNIUM INORGANIC CHEMICALS LTD (ACN 008 683 627)

Third Respondent

Office of the Registry
  Perth  No P12 of 2009

B e t w e e n -

MILLENNIUM INORGANIC CHEMICALS LTD (ACN 008 683 627)

Appellant

and

TERESA ELLIS AS EXECUTOR OF THE ESTATE OF PAUL STEVEN COTTON (DEC)

First Respondent

THE STATE OF SOUTH AUSTRALIA

Second Respondent

AMACA PTY LTD (ACN 000 035 512)

Third Respondent

FRENCH CJ
GUMMOW J
HAYNE J
HEYDON J
CRENNAN J
KIEFEL J
BELL J

TRANSCRIPT OF PROCEEDINGS

AT CANBERRA ON THURSDAY, 5 NOVEMBER 2009, AT 10.17 AM

(Continued from 4/11/09)

Copyright in the High Court of Australia

__________________

FRENCH CJ:   Yes, Mr Walker.

MR WALKER:   Your Honours, the submissions I am going to put this morning are organised around the general attempt to persuade your Honours that what was done at trial and the way in which that was dealt with by the majority in the Court of Appeal, properly understanding their Honour’s reasons, fits well and truly within what this Court has treated and what has been treated by courts following this Court repeatedly as the proper approach to what may legitimately be inferred from evidence in cases such as the present where direct observation of cause and effect is beyond the scope of available knowledge.

We accept, with great respect, that the issue in this case is whether or not error can be shown – it does not matter whether it is legal or factual in nature – in the manner in which the inference was drawn that the negligent exposure to asbestos, on the part of each of the appellants, of Mr Cotton materially contributed to the lung cancer which constituted damage and which caused damage to my client.

It is, in our submission, critical therefore to start with the material that was before the trial judge and reconsidered by the Court of Appeal, largely as common ground in relation to the carcinogens in question, and I call them carcinogens because the common ground very much included that the medical scientific knowledge in this area had progressed well beyond mere statistical associations produced by epidemiological studies of the relative incidence of the contraction of lung cancer in people with different forms of exposure to, among other things, tobacco smoke or asbestos dust.

FRENCH CJ:   Does the evidence of, if I may call it, a plausible biological mechanism for the impact of asbestos on the aetiology of lung cancer rise any higher in this case than giving some, if you like, factual underpinning which would give confidence in drawing inferences from the epidemiologically derived risk factors?

MR WALKER:   In essence, they do go a bit further, but that is the nub of it.  Can I try to capture a number of different points in answering the Chief Justice’s question?  I will, of necessity, have to elaborate parts of this answer by reference to the evidence and the findings, to which I will then later go.

I said in opening my address yesterday that at least one reference by their Honours in the majority in the Court of Appeal to epidemiological evidence is most unfortunate.  Can I elaborate that in order to answer the Chief Justice’s question.  Your Honours appreciate that it is volume 4, page 1513, paragraph 336 to which I am making reference here, and perhaps I should deal with this once and for all now.

If that expression in the second line, line 10 on the page, “the epidemiological evidence”, was to be taken in what I had accepted is perfectly ordinary English meaning in the context of this case, then it is an unaccountably wrong statement by their Honours.  But that it should be not be so understood can be seen from a number of things, and first within the very same paragraph itself, one can see that there is a reference to the evidence being based on a false assumption.  None of the epidemiological evidence in relation to the recorded patterns of incidence of lung cancer among smokers and people exposed to asbestos has ever been described by any evidence in this case as being based on any false assumption of any kind.  That is the first clue.

The second clue is in the last sentence of the same paragraph, just above line 20, where there is the reference to the “derivative attributable fraction”.  That derivative attributable fraction is in fact the epidemiological evidence so‑called, and unfortunately so‑called in the first sentence of 336.  Further, in the middle of paragraph 336 one sees a reference to it being:

determined that tobacco smoking and all asbestos exposures operated cumulatively –

another unfortunate word I have to come back to.  That, as we all know from the material in the case, has been determined by and only by epidemiological evidence, indeed, the common ground as to what it meant.

So in that paragraph, epidemiological evidence is in fact referring to the “derivative attributable fraction” exercise, which ironically is not epidemiology in the ordinary sense of that expression because it has nothing to do with studying the incidence of outcomes or the relative distribution of precedent exposures, which is the hallmark of epidemiology whether it is a retrospective study or a prospective study.  What it is is an arithmetic or mathematical manipulation – I do not use that word derogatorily, hence it is a derivation - from numerical data produced by those observational studies.

GUMMOW J:   You are challenging paragraph 336.  Is that right?

MR WALKER:   No, I am saying that their Honours cannot have meant all the epidemiological evidence when they said “the epidemiological evidence”.  It is an unfortunate use of the expression.  The context shows it cannot be understood as meaning the ordinary meaning of the epidemiological evidence because they are, in fact, using the epidemiological evidence.

The only one that has a false assumption, that false assumption, as your Honours appreciate from the discussion yesterday and from all the material, particularly by the trial judge, to which I will come, was concerning so‑called independent operation.  It is the false assumption which is belied, in fact, by the epidemiological evidence that shows that tobacco and asbestos as a combined carcinogen – that is a singular – is more dangerous than tobacco as a carcinogen and much more dangerous than asbestos as a carcinogen.

GUMMOW J:   You do not need a notice of contention to embark on this part?

MR WALKER:   No, it is just a reading of the expression.  They are not, in fact, holding that the epidemiology is saying that tobacco and asbestos is a more dangerous carcinogen than tobacco alone.  They are not, in fact, holding that that is irrelevant.  They are using that in the very same paragraph, so I do not need a contention.  It is language not reasoning.

GUMMOW J:   Well, I am afraid this is a Court of Appeal – are we not entitled to take at face value what they are saying.

MR WALKER:   Yes, your Honour, and what I am saying is ‑ ‑ ‑

GUMMOW J:   It is not some administrative tribunal with non‑lawyers in it.

MR WALKER:   Your Honour, what can I say?  This is language that is unfortunate, but from the internal context and from the reasoning of their Honours, it is plain that they were not putting to one side the studies which it was common ground show that tobacco and asbestos is more dangerous than tobacco.  They are actually using that, for example, to ascribe falsity to the so‑called assumption because it is that epidemiology that shows that when they are both in the exposure of the individual they do not operate independently.  I am going to come back to that question later.

In order to answer the Chief Justice’s question, yesterday there was a passing comment by Mr Abbott in relation to the expression “plausible” or “plausibility” for the laboratory observations.  That was faint praise.  The short answer to that is, not so.  It is the term used in reasoning from epidemiological work for the supportive or corroborative physical sciences – the laboratory work, usually on unfortunate rodents, sometimes at cellular level, mutagenesis, molecular work - to provide an acceptable biological explanation that renders appropriate reasoning, inferential reasoning that a statistical association between exposure X and outcome Y is more than just coincidence and has a biological explanation.  That is what it means.

FRENCH CJ:   Does that mean the answer to my question is yes?

MR WALKER:   That is why I said the nub of it is yes, but there is more to it than simply what your Honour put to me because in this case there is also that biological material, that laboratory work – and it is not in people like Mr Cotton, it is in rats and cells and the like.  What that shows is what was common ground.  People in this case, including in the last two days, are not talking about tobacco or asbestos as putative carcinogens.  Everyone is treating them as proven for the purposes of medical science and certainly, for the purposes of this case, it is accepted that they are carcinogens; they do cause cancer, not in every case, of a person exposed to them.  Nor is it true that cancer is in every case the outcome of exposure to tobacco or asbestos or both of them.  That is why multiple causation and multifactorial diseases present the problems for legal causation that this case illustrates.

KIEFEL J:   If you say that the Court of Appeal did not put aside the epidemiological evidence what conclusion do you say that the court reached upon which it then approached causation?

MR WALKER:   I did not catch the last part of your Honour’s question.

KIEFEL J:   What conclusion do you say that the Court of Appeal reached and used in applying theories of causation?

MR WALKER:   They certainly used the epidemiology implicating tobacco and asbestos as a more dangerous carcinogen than tobacco.  That is the first thing.

KIEFEL J:   All right.  Did they, however, put to one side the views expressed by, say, Professors de Klerk and Berry and favour the view expressed by Dr Leigh?

MR WALKER:   No.  They use all three.  Now, why I say that is because Professors Berry and de Klerk in manners that I will come to, if I may in more detail in a moment, are both at the forefront of the expert evidence for the common ground proposition that tobacco and asbestos was more dangerous than tobacco and, in particular, was more dangerous than the mere addition of tobacco and asbestos, the so‑called multiplicative effect, to which I will come.  They were to the forefront of those who gave that evidence.

KIEFEL J:   I appreciate that, but for the moment I am more interested in what the Court of Appeal is concluding, as you read it.  They seem to focus at appeal book 1513, line 42 on Dr Leigh.  Now, it may be that Dr Leigh’s bottom line in relation to what he calls that part that asbestos played in causation is not so different from the conclusions reached by Professor Berry.

MR WALKER:   Quite so.  Your Honour has put your finger on it.  Leigh, in fact, uses the same material and uses further material.

KIEFEL J:   In terms of the evidence, is the bottom line that Dr Leigh considered that regardless of whether you apply a model which multiplies the risk factors that asbestos could be said to have played a part in the outcome of cancer to the extent of between two and 20 per cent?

MR WALKER:   Unquestionably, Dr Leigh’s conclusions shorn of the spurious numerical expression – spurious because of the unreliable data – unquestionably that is used by both the trial judge and the Court of Appeal.  However, it did not stand alone and it was not in competition with ‑ ‑ ‑

KIEFEL J:   But do you agree that that is the conclusion reached by Dr Leigh?

MR WALKER:   I certainly accept that Dr Leigh proceeded on the basis that the epidemiology and the laboratory work – and I will come to both – supported the view that a person exposed to both asbestos and tobacco – who has lung cancer - has suffered it because of the effect of both of them, which their Honours describe in the majority, and again an unfortunate expression but easily explained in context, as being a so‑called cumulative operation.

KIEFEL J:   I know that you do not agree with that but if - I am reading from appeal book 912, the summary of Dr Leigh’s report where he says that taking asbestos exposure and smoking together, he says that they caused lung cancer.  Put his aside his reference to the word “caused”, the last sentence is:

on an apportionment model, the fraction of causation attributable to asbestos is 2‑20%.

MR WALKER:   Yes, and that is the mathematical manipulation that, in our submission, is beside the point for the legal question.  The legal question is whether the ‑ ‑ ‑

KIEFEL J:   But that is the mathematical apportionment from a model that assumes multiplication, is it not, which is the highest you can go.  He is saying it does not matter what model you use, the two to 20 per cent will give you your variations in the model that you have chosen.  The attribution of asbestos to causation can only be at its highest 20 per cent.  Is that not correct?

MR WALKER:   No, it is not correct to answer the legal question for the following reason ‑ ‑ ‑

KIEFEL J:   The legal question is quite a different matter.

MR WALKER:   It is, that is what I am saying.  Attributable fraction is not the legal question is my point.

KIEFEL J:   He is not talking about an attributable fraction relating to the relative risk, though.  He is talking about the fraction from which you may derive from the combined effects of tobacco and asbestos, and if you use a multiplicative model, is he not?

MR WALKER:   Your Honour, with great respect, the two to 20 per cent is an attributable fraction exercise.  That is the language of his statement there.  The relative risks are clear and it is common ground that the relative risk of tobacco and asbestos is greater than the relative risk of tobacco, and it is greater than the mere addition of the relative risks, respectively, of tobacco and asbestos.

KIEFEL J:   For the purposes of Dr Leigh’s summary, we have moved well beyond that.  He has determined relative risks, he has determined attributable fractions of those risks, he has been questioned, he has referred to the combinations working together and he is saying that however you put them together asbestos can only be responsible for 20 per cent, is it not, in terms of probability of outcome?

MR WALKER:   Your Honours, what I want to say is this.  First of all, the reference to probabilities there has no sensible application to the legal inquiry which is after a person has suffered.  We are no longer talking about a risk for him.  It has fallen in.  That is one of the fallacies behind using attributable fraction at all.  The second point is attributable fraction is not a direct product of comparing relative risks, and you can see that from the mathematics that is exposed in the various witnesses.  Your Honours can see the steps. 

The third thing is that multiplication is again an unfortunate ambiguous word but is not the fault of any judge.  It is because it happens to be used in the evidentiary material in two quite separate senses.  There is first the sense in which it is used in the expression “multiplicative”, that is more than additive to describe the biologically plausible, accepted on all hands, combined effect of tobacco and asbestos to be in itself a carcinogenic entity, if you like, more dangerous than tobacco and certainly more dangerous than tobacco and asbestos simply added together, which is what they would be if they were truly operating simply independently.  They both operate and you would simply add the effect.

GUMMOW J:   Mr Walker, I am sorry to interrupt you, but page 912, line 31, do you press the words - after “I believe”, do you press the words that follow “that asbestos exposure and smoking together caused Mr Cotton’s lung cancer”?  It seems to me to have been inadmissible.

MR WALKER:   I am mercifully not trial counsel, but of course your Honour, with great respect, is right.  It is either inadmissible or really would have to be seen as incapable of concluding the issue.  I accept that of course.  But am I saying that Dr Leigh’s evidence conveys his belief or opinion that are expressed that the exposure to asbestos and smoking were causative, both of them, in the lung cancer?  Yes. 

FRENCH CJ:   Can I just come back to some of your answers to Justice Kiefel, and I am teasing out what I think is pretty close to explicit in what you are saying and that is that there are two different kinds of statements and processes that we are concerned with here.  First of all, there is the question what is the probability that asbestos exposure will, in a particular case, lead to cancer?

MR WALKER:   That is right.

FRENCH CJ:   That is the risk question, that is the prospective question.  Then there is what you would call the legal question:  what is the probability that the conclusion that this exposure led to the cancer is correct?  To succeed you would have to show that it is on the balance of probabilities ‑ ‑ ‑

MR WALKER:   That is right.

FRENCH CJ:   So really we are back to the question of what use could properly be made of risk, knowledge of underlying biological mechanisms, the fact of the cancer, and drawing an inference about which one can be confident of its correctness on the balance of probabilities.  So really it boils down to what was available to support the inference.

MR WALKER:   Yes, that is why I started as I did this morning.  We accept that is the exercise, but I do, with respect, need to continue, if I may, to try to answer Justice Kiefel’s question. 

KIEFEL J:   Before you do could I add some questions, because I really would like you to come to a statement, if you are able, as to the extent to which you could take the scientific or the epidemiological evidence and the conclusion for the basis upon which the Court of Appeal used any such evidence.  On one view, as I have indicated, the Court of Appeal appears to have approached the matter by putting to one side such evidence, in order to – I do not mean that as a deliberate outcome – but with the result that Dr Leigh’s general expression of opinion about causation was all that was left from a clinician’s point of view.  Now, that is one way in which one might view the Court of Appeal’s approach.

If, however, you say that they have used the epidemiological evidence and they appear to have approved Dr Leigh, what do you say the statement in the last sentence of his report stands as and is it not – whatever it stands as – consistent with Professor Berry’s figure, which I think was about 23 per cent for the interaction of – well I should not use the word “interaction” – the part that asbestos might play when it interacts with tobacco?

MR WALKER:   What the law is concerned with is whether the defendant’s conduct materially contributed to – I will call it – the plaintiff’s damage.  Where there are multiple causes and that already assumes something or treats something as demonstrated if they are multiple causes for the purposes, in particular, of contribution between tortfeasors, between defendants, language sometimes used in medical science or research transfers to the courtroom and they start talking about relative causal potency or similar expressions.  But, of course, if they are multiple causes they are all causes and the defendants are quarrelling about contribution because the causes have all come home in the damage for which damages have been awarded.

That is why if in the contribution action there is a 90 per cent attribution to one person on account of what I will call causal potency - I am leaving aside moral blameworthiness for the moment - then it does not mean that the person who has been spared the burden, assuming the contributing tortfeasor is solvent, of all but 10 per cent of the damages is in any way removed from the class of persons whose conduct caused the plaintiff’s loss.  Attributable fraction is really no more than, from a different discipline, that is medical science and biostatistics, mostly used for public health purposes.  It is nothing more than assessing what I will call relative causal potency among multiple causes, but they are causes, and it is not a figure that says “and this means they are probably not causes”.  It is a figure that says “their relative potency as an accepted cause is of a lesser order”.

In a sense, this is either a scientific or a philosophical or a statistical inquiry of no moment in a court except to the extent that the figures are so striking that for the legal inquiry the contribution could not be said to be material and, in our submission, anything which contributes to a relative risk being so considerably higher as asbestos does when combined with tobacco, over and above tobacco and, as it happens, also over and above tobacco and asbestos simply independently operating additively, cannot be said not to have made a difference that matters, thus a material contribution.  I will come back to what I call some clinical matters involved in that, including from Professor Musk.

KIEFEL J:   But Dr Leigh was the plaintiff’s witness, is that right?

MR WALKER:   Yes.  The witnesses, however, tended not to disagree with each other on fundamentals.

KIEFEL J:   Quite so.  So from the plaintiff’s perspective, what was the plaintiff going to make of the summary, putting aside the references as has been pointed out to inadmissible statements about causation?  What could the plaintiff make of Dr Leigh’s conclusions?

MR WALKER:   The last sentence – and I do not know the forensic history as to why the first sentence is there, but in any event, it is – Dr Leigh is not doubting causation.  He is not saying there is only a 20 per cent chance that this was causal.  He is saying it was causal but its potency is two to 20 per cent.

FRENCH CJ:   I do not understand what terms like “fraction of causation” mean.  Is that a normative statement or what?

MR WALKER:   It is an attributable fraction of an established causation.  You have got the causes, they are multiple.  If you were inclined to make these numerical statements, you have attributable fraction calculations.  We said below, the trial judge accepted, the Court of Appeal majority accepted, and I am arguing that that has nothing to do with the material contribution inquiry which is the legal question unless and until, unless and until, the figures are so striking that materiality cannot be demonstrated on the balance of probabilities.

KIEFEL J:   Let me put it another way.  What is the highest that Dr Leigh’s evidence could be put for the plaintiff?

MR WALKER:   That is your Honour’s question?

KIEFEL J:   Yes.

MR WALKER:   That tobacco and asbestos operated together in this man to cause his lung cancer.  Next, that asbestos played a part in producing that because of the epidemiology and laboratory work which is in the earlier pages of his report showing that that is a more dangerous exposure than tobacco and asbestos operating independently thus only additively.  Third, and this is what we draw from Dr Leigh’s evidence, that shows a material contribution by asbestos to his lung cancer.  That is the way we use, to use your Honour’s expression, at its highest Dr Leigh’s evidence to support the plaintiff’s case.

HAYNE J:   The point to which attention might usefully be directed is the second of the steps?

MR WALKER:   Yes.

HAYNE J:   The second of the steps that both are implicated?

MR WALKER:   Yes.

HAYNE J:   Can I come at it from this angle, Mr Walker.  The epidemiologists, amongst other things, take a group of lung cancer patients and identify exposures and levels of exposure to carcinogens, do they not?  That is part of the data they take to account.

MR WALKER:   Your Honour, I fear over the years I have learnt too much about it.  That is just one of the many ways they can design a study.

HAYNE J:   I understand that, yes.

MR WALKER:   Yes, they could do that.

HAYNE J:   Because those who are exposed both to tobacco and asbestos have an incidence of cancer greater than would be predicted by adding the singular risks, the exposure to both is treated by the epidemiologist as, one, significant – and we come to what the significance is – two, warranting the conclusion, putting it in neutral terms, that both are implicated.

MR WALKER:   Yes.

HAYNE J:   Three, expressing that conclusion in terms of causation.

MR WALKER:   Yes.

HAYNE J:   It is at this point that I think your argument must confront the need to differentiate between the way in which the scientist deals with questions of causation and the legal issue that arises in this case, was exposure negligent, exposure to asbestos a cause of the plaintiff’s injury?

MR WALKER:   With great respect, I accept all of that, including a statement of what I need to confront.  I have tried to do that in my answers to Justice Kiefel where I have pointed out that the attributable fraction exercise only operates of any use at what I will call the margin of being at the end of a spectrum because it assumes causal effect – it takes, I should say, causal effect.

HAYNE J:   Be it so, the point that you have to confront at the legal significance of causation is that the numbers that are revealed by the epidemiological studies show that asbestos is a – attempting to put it neutrally – a small cause, small chance of causing this kind of cancer.

MR WALKER:   Can I prefer your Honour’s first formulation to your second?

HAYNE J:   I understand why you do, but it is a small chance of causing, overwhelmed by tobacco.  That is the case against you.  That is the case you have to meet.

MR WALKER:   No.  It is the case against me but what the evidence shows and the common ground evidence shows, it is a small contributor.  It is a contributor ‑ ‑ ‑

HAYNE J:   No, to a population result, yes.  It is a small contributor to a population result of whatever your population is.  That I understand.  But we move from population which is the field of the epidemiologist to particular and chance becomes the critical thing, not incidence in population.

MR WALKER:   Can I suggest, with respect, that chance and incidence in population are in fact the same.  The chances are calculated by observing, counting and comparing the incidence of outcome or exposure.  That is what chance is.  For the plaintiff who has suffered the disease, chance or risk is no longer in question.  They have suffered.  What the chance or risk material, which is the epidemiological biostatistical material, is used for is as part, and in a case like this a very large part, of the scientific demonstration and acceptance, common ground in this case, that exposure to tobacco and asbestos is dangerous to the extent I have described and should be treated as implicated biologically.  It is not a mere association statistically.  It is not a coincidence.  It has physical, physiological meaning.  They are both carcinogens independently and combined they represent a carcinogenic entity more dangerous than them operating independently additively.

The chance material, the increased risk material, justifies a statement that in another kind of disease, such as the study of germs and infections, would have been produced by physical scientific observations, namely, it is a tenet of medical science that X causes or can cause Y.  That is what the epidemiology does primarily in this case.  It shows that tobacco and asbestos can cause the lung cancer.  He has the lung cancer.  The question now is, more likely than not, did the asbestos materially contribute to it?  That is the only question.

We accept that the medical science largely composed, and in this aspect wholly derived from the epidemiology, shows that on any view, and regardless of spurious or otherwise precision in the numbers, tobacco is by far the more important or potent causal contributor to the lung cancer.  There can be no doubt about that.  One sees it from a comparison of the relative risks for asbestos alone, tobacco alone and the combination.  The attributable fraction calculations are just a mathematically expressed way of making that same point.  But the attributable fraction statements do not talk about the chance of the asbestos having operated, they talk about the potency of its actual operation. 

It does not say there is an 80 per cent chance that the asbestos had nothing to do with this case, if the figure be taken as 20 per cent.  It says that it is responsible only 20 per cent for that to which it contributed by way of cause.  So it does not defeat cause, it in fact accepts cause and then describes its relative potency.  We accept what all the figures, whether you do it by way of attributable fraction or whether you do it by way of expressing the relative risks, we accept what it says about the comparison between tobacco and asbestos.

To use the language of the Chief Justice in the Court of Appeal in a passage to which I want to come, we accept that tobacco was the predominant contributor to the lung cancer.  We would also accept, perhaps wincing a bit, his epithet that the asbestos was the minor contributor or, as we put in our written submissions, was subsidiary to the tobacco.  But the point is that those epithets are still attached to the noun that says they are a contributor.  So they did cause, they contributed, and the question in law is whether they did so so as to attract the all important epithet material.  It is at that point that it is, in our submission, important to emphasise, I fear, by way of repetition and variation, that that is not a function of any chance or risk calculation.

By the time one is talking about predominant minor, predominant subsidiary in an individual for whom no question of chance or risk remains, it has eventuated, it is the medical science which had used study of chances of risks in populations to say there is a pattern here and it is a pattern that says tobacco and asbestos will make a difference in your lung cancer outcome and there will be more tobacco and asbestos exposed persons in the lung cancer class than there are in the general population or there are more lung cancer people in the tobacco and asbestos class than there are in general population.  It depends on how you design the study.

That was all common ground, that use of chance or risk.  I stress the probabilistic statements that have been expressed in legal submission based upon the attributable fraction arguments are not statements which can truly be seen as reflecting on the chance of asbestos having played a part.  In truth, they can only be attribution of a relative potency, it having played a part.  Our first task, of course, is to persuade a trial judge and now your Honours that it played a part.  The best way we can demonstrate that it played a part is to say, given what medical science says, namely, the lab work, et cetera, shows on its own it works the cellular, et cetera, effects which are though to be implicated in oncogenesis.

Your Honours have the passage at 901 in volume 3 of the appeal book, Dr Leigh’s report, where there is a reference to the laboratory work, that is the top half of that page, which suggests how there may be interaction between these two known independent carcinogens in a way which, when they are in a combined exposure, shows both are interdependent or, as their Honours in the majority called it unfortunately, cumulative.  That is why I call them a third carcinogenic entity and the only one to which this man was exposed.  He was not exposed only to tobacco, he was not exposed only to asbestos, he was exposed to the combination.  So we say that the so‑called increased risk or chance material, the epidemiology from the various study populations, has led medical science and all the experts in this case on both sides and, we think, all the judges, to the proposition that tobacco and asbestos is carcinogenic as a combination. 

When we come to ask the question, but did the asbestos materially contribute to this man’s lung cancer, and we accept that is the question, the first and robust answer is, well, the medical science says that when you add tobacco and asbestos, apparently they operate together.  That means they are both operating.  It is not as if one says, feel free, this is your cell, I will not touch it.  They are both operating.  That is produced by the observations that they apparently produce an outcome of lung cancer in greater relative incidents compared with unexposed populations than would be the case if they were simply operating, as it were, turn and turn about, case by case, independently or on their own.

That is why there is, in our submission, good medical science to support the proposition, both exemplified by and explained by Dr Leigh, accepted by the courts below that in this man much more likely than not both operated together because the medical science shows that when people are exposed to both there is this extra danger of the outcome.  By extra danger I do not mean unrealised possibilities, I mean that they have countered realised events sufficiently often and compared them sufficiently often to show there is what the statisticians call an excess in that group, an excess leading to the relative risk, higher for the combined entity than for the two separate entities operating independently and just added together and that is what ‑ ‑ ‑

BELL J:   You have used the expression “in this man”.  You have used it twice this morning and you have used it in your written submissions.  What is the evidence touching on this plaintiff that gives any content to that?  We understand that this plaintiff is a person for whom the risk came home, that is ‑ ‑ ‑

MR WALKER:   Sorry, for the deceased, I think.

BELL J:   Yes, yes I understand, Mr Walker.  We understand that this person suffered lung cancer.

MR WALKER:   That is right.

BELL J:   What evidence touched on features peculiar to him to give any relevance to the reference in your written submissions at paragraph 56 by way of illustration:

given the finding below that, in this man, the multiplicative effect of tobacco‑and‑asbestos was the cause of his lung cancer ‑ ‑ ‑

MR WALKER:   Now, it is common ground that though a deal is known about lung cancer - that is, it is not completely mysterious - there is also a lot that is not known and is not capable of being known at the moment, perhaps forever.  In particular, one could not by biopsy or autopsy and techniques such as histology or other investigation using physical scientific methods attribute one person’s lung cancer, let alone Mr Cotton’s, to one or other of the certainly multiple and almost certainly equally unknown number of environmental or behavioural influences, putatively suggested to cause lung cancer. 

GUMMOW J:   Now, you used the word “robust” I think in relation to inference. 

MR WALKER:   I think I did, yes.  Perhaps I should withdraw it.

GUMMOW J:   In Wilsher’s Case [1988] AC 190, Lord Bridge said:

Adopting a robust and pragmatic approach to the undisputed primary facts of the case, the majority concluded that it was a legitimate inference of fact that the defenders’ negligence had materially contributed -

Is that the area in which we are?

MR WALKER:   I hope not, for this reason.  We are just asking for an inference to be drawn.  Now, take those words “robust” and “pragmatic”.  It is difficult to understand a court ever describing itself as not pragmatic and so that could be put to one side.  The word “robust” is rather more difficult because it might be a euphemism for a bit rough and ready ‑ ‑ ‑

GUMMOW J:   Yes.

MR WALKER:   I hope courts would not be willingly self‑describing themselves thus.  On the other hand, it is perhaps ‑ ‑ ‑

GUMMOW J:   His Lordship also used the word “legitimate” inference.

MR WALKER:   Quite, on the other hand ‑ ‑ ‑

GUMMOW J:   The question is what processes of inference are legitimate and what are illegitimate, I wonder?

MR WALKER:   Yes.  I wonder if your Honours would forgive me.  I am trying to work out where I should be up to at the moment.  Could I finish just answering Justice Bell’s point ‑ ‑ ‑

GUMMOW J:   What I am asking you is linked to that question because you want to connect the primary facts to this man, and how do you do it?  By inference.  What sort of inference?

MR WALKER:   Yes, and that is what I am about to attempt in answering both your Honours’ questions.  So that there was nothing and nobody ever suggested there could have been anything that said you can look at the cancerous cells and say that is a tobacco‑caused cancer.  Now, we think, pace some things that fell from South Australia yesterday, nobody has ever in the course of this litigation suggested that that is a reason for a plaintiff to fail.  But it does not dispense us from still having to prove on the balance of probabilities “in this man”, to use that expression that has attracted your Honour’s attention, the multiplicative characterised combined entity, carcinogenic entity caused the lung cancer. 

Now, it is certainly true that the courts below found that to have been the case.  That was the question.  Was Mr Cotton’s lung cancer materially contributed to by the asbestos?  Yes, came back the answer, because he was exposed to tobacco and asbestos and asbestos was a material contribution to that combined entity.  That is the reasoning that we submit is in accordance with the orthodoxy that we have referred to in our written submissions and I referred to in opening address yesterday.

KIEFEL J:   Is not a difficulty though for any inference that you seek to draw, however you describe it, that tobacco and asbestos on the scientific evidence do not necessarily interact, and if they do not necessarily interact do you not have to look to the chance that they do interact?  Is that not your starting point?

MR WALKER:   No.

KIEFEL J:   And is that not the area where you might then take yourself into the realm of an increasing risk?

MR WALKER:   No is the answer to all of that.  Your Honour, there is no evidence, observational or otherwise, that they do not necessarily interact.  That is a logical possibility left open by ‑ ‑ ‑

KIEFEL J:   I thought that was the evidence of Dr Leigh who said that they simply do not know how and why.  They interact so you cannot come to anything other than there are some hypotheses which he regarded as plausible but no one could take it any higher than that.

MR WALKER:   Your Honour, that is my point.  It is a logical thing that cannot be excluded that they do not necessarily interact, which comes from the lack of knowledge of what I will call mechanisms.

KIEFEL J:   No, it comes from the proven fact that they act independently.  They can, of themselves, be a cause.

MR WALKER:   Your Honour appreciates that does not logically mean that when they are both present that one may not be acting and the other may be.

KIEFEL J:   No, it is just that they do not know how they do.

MR WALKER:   We just do not know ‑ ‑ ‑

KIEFEL J:   Your premises are tobacco alone may cause lung cancer.  Asbestos alone may cause lung cancer.  The probabilities are quite different.

MR WALKER:   Yes.

KIEFEL J:    They may in combination act to cause lung cancer.  It is how you deal with the latter that is difficult and that is, I thought, where the epidemiologists were trying to apply probabilities to try to give an outcome.

MR WALKER:   No, the attributable fraction is not the chance that they did operate together.

KIEFEL J:   That they might.

MR WALKER:   No, the attributable fraction is not a chance that one or other of them did operate in fact.  Attributable fraction is a potency distribution.

KIEFEL J:   I am not saying to the particular person.  I am not extrapolating it.

MR WALKER:   No, in a particular person I am talking about.

KIEFEL J:   I am saying these studies show that in a given group when something has occurred they can attribute it.

MR WALKER:   Could I put it as directly as I can.  The  20 per cent, to take that figure that Dr Leigh concludes with, that does not mean that in 20 per cent of the cases of combined exposure only in 20 per cent of them did asbestos play any part.  That is not what it means.

KIEFEL J:   No.

MR WALKER:   It says, having played a part in this curious way that that mathematical presentation involves, it had a 20 per cent contribution, if you like, but the contribution, that is, having played a part, is a premise of those calculations.

KIEFEL J:   It is a subdivision, is it not, of the combination that we have got to.

MR WALKER:   Exactly.

KIEFEL J:   I understand that.  I do not have a difficulty with that.  But is your difficulty not with the fact that the likelihood of the combination is not high?

MR WALKER:   No, the likelihood of the combination is higher than anything else in this case.  Let me explain.  Tobacco and asbestos together, the combination, is accepted as the most dangerous of those that have been talked about.  It is not necessarily the most dangerous thing to which, if exposed, thought to cause lung cancer, I think that is benzene, but in this case there are candidates for a causal explanation of what in fact was the lung cancer.

The only thing that in fact he was exposed to, relevantly, that is, of all the others, background risk, autogenous possibilities, unknown chemicals, et cetera, the parties did not pursue them.  Neither plaintiffs nor defendants raised candidates other than the combination and its components.

KIEFEL J:   I do not want to take you up too long.  I have no difficulty with the notion that when the combination takes effect it has the multiplying effect that the witnesses speak of and maybe it is higher, but is not the critical question for you whether the likelihood that the combination did affect because you have this difficulty that there is not necessarily an interaction?

MR WALKER:   No, because the higher relative risk close to multiplicative is a demonstration that where there is a combination, it, more frequently than for any of the others that matter, produces the lung cancer.  So, in other words, it is not a freak or unfortunate event that you suffer from the combined effect of them.  It is the more frequently, the usual thing that one – this is the inference to be drawn – the usual outcome of the combined exposure is lung cancer from combined effect because, when you look at the figures, it comes out to be near multiplicative and more than additive.

FRENCH CJ:   You have three alternative explanations relevant to this case for the contraction of the disease.  One is exposure to tobacco alone.  An alternative is exposure to asbestos alone.  A third alternative is the combined exposure.  What you need to get to is a situation that on the balance of probabilities combined exposure is the correct explanation.

MR WALKER:   Did the trick.  Yes.  It was said in our written submissions ‑ ‑ ‑

HAYNE J:   You should not assume I accept that you divide the world into three.  You have to add the fourth, unknown cause.

MR WALKER:   I think I probably started with that in our written submission, your Honour, and that is why I have just said – there could well be more because you might subdivide a fourth into external influences and then what is called autogenous lung cancer which probably means something we absolutely know nothing about.  What we had in this case was, starting with the four that we have posited our written submission because, with respect, what Justice Hayne has said is a starting point, the way in which the parties cast the issues meant that the fourth was winnowed out quickly, that is, the defendants did not propose that any fourth class was a reason to resist the finding which we sought.

HAYNE J:   This is the step that is critical to your argument, is it not, Mr Walker?  See paragraph 52 of your written submissions.  Critical to your argument is the step of winnowing down to your only two candidates in the field, is that right?

MR WALKER:   Yes, your Honour.

HAYNE J:   That, I suggest to you, is a legal fallacy.

MR WALKER:   No, your Honour.

HAYNE J:   It is a fallacy because, firstly, though it is denied there is a shift in burden of proof, you say the defendant has pointed only to these two as candidates.  But the critical question for your side was, was the defendant’s negligence a cause, et cetera?

MR WALKER:   Yes.

HAYNE J:   That is not to be answered, I would suggest to you, by taking a 100 per cent of a field.  Observing of less than the 100 per cent, let us say – and I pluck the figures at random, not by reference to evidence – that 15 is larger than 10 and because these are the only two candidates on the table, 15 being larger than 10, therefore I have proved more probable than not.  Once you have stripped out the 100 per cent down to consideration of the 25 in this very tendentious example I put to you, you have slipped. That is the slippage which I suggest is apparent in paragraph 52 of your argument.

MR WALKER:   Your Honours, obviously I have to confront that directly.  I will try and persuade your Honours that there has been no fallacy or no slippage but, with great respect, Justice Hayne has pinned correctly premises on me.  Yes, that is what we are doing.  Let me seek to rehabilitate its merit.  There are many ways in which sudden cardiac failure can cause death, probably not all known. In Forst’s Case a question arose as to whether the possibility of immediately antecedent physical exertion could be an explanation that ought to be accepted on the balance of probabilities given the striking sequence of events, et cetera. 

Dupuytren’s contracture, we know.  One in 20 was the estimate by the expert as to how often it was associated with the kind of trauma which would apply to the plaintiff’s position.  So, in other words, most of them were not so explained and obviously most people with traumatic use of their hands do not suffer Dupuytren’s contracture.  But that reference to the possibilities, in our submission, is useful only because it is the means by which the medical scientific experts, united in this case, described the medical possibility, biologically grounded, that the exposure in question caused the outcome in question.

Then when it comes to the legal question - using the same material of course, plus more – as to whether the plaintiff satisfies the court on the balance of probabilities that is what did happen in this case, then it is appropriate to have regard to the way in which the parties, particularly in the way in which they present the expert evidence and test the expert evidence of each other, eliminate as not relevant to their dispute possibilities which the science leaves open but the facts of the case do not present as worth fighting.  So in this case some untraceable ghastly chemical from a drycleaner, well known possibly to be implicated in lung cancer, is not pursued by anything in the way in which the parties join issue, and the experts all agree that – in fact the appellants combine to say it is the tobacco that caused his lung cancer.

They do not leave themselves with a purist and unrealistic forensic position of saying it could be any one of a thousand IARC‑named carcinogens plus all the unknown ones.  For those reasons, in our submission, just as in Forst’s Case and in Fernandez’s Case there are observations about possibilities that did not have to be considered because they were not seriously pressed, so in this case, lung cancer at 42, Professor Musk had something to say about that as a clinical observation against the background of the special extra danger of tobacco and asbestos, and that is one of the facts that gets added to.  I mean this is, of course, not a case of simply making an inference from so‑called increased risk by epidemiology.

When one put all of that together, it is clear that no one – and there is no reversal of onus of proof here – none of the experts, plaintiff or defendant, suggested that there was a worthwhile explanation of the lung cancer outside his exposures to tobacco and asbestos.  That does not mean that it has been scientifically proved by the judgment of the court that that is what caused it.  We will never know, and that is something that the experts and the courts hitherto have accepted in the case of unknowable ultimate causal inquiries where one has to proceed by and only to the extent of legitimacy of the inferences from the indirect material.  That is how the fourth came to be eliminated.

The third was fairly rapidly eliminated, and no appellant would resist that, that is, the notion that asbestos alone caused the lung cancer.  That was one for us in a heroic moment to undertake, and it was not undertaken, or at least not persisted in, and for reasons which are plain to demonstration on the face of the expert material on our side, as well on the other side.  It can hardly be held against us that we have left out or slipped, let alone reversed an onus, by declining to seek to prove, to persuade the court that on the balance of probabilities it was asbestos alone that caused the lung cancer, though of cause scientifically, the accepted sufficiency of the exposure to have done so means that that remains a possibility and still a possibility that cannot be excluded if one talks scientifically, but it can forensically in the joinder of issue between parties concerning liability for a tort be eliminated by the way in which the evidence is presented and the factual issues are argued.

That then left the two candidates that we have referred to in our written submissions.  The first thing to be said about the two candidates – and this picks up an expression of the Chief Justice yesterday “competing causes” – is that in a sense they were competing but only in the legal forum.  They did not compete in nature.  There was no tobacco alone.  It was tobacco and asbestos.  Nor did anyone suggest they were alternative in the sense that Wilsher’s Case illustrates, namely, if the event was caused by A, then it was not caused by B, C or D, and ringing the changes on that, alternative in the sense of being mutually exclusive. 

Obviously no one was suggesting anything in the nature of some bizarre or, one might say, hoped for protective effect of smoking if you are exposed to asbestos or of asbestos if you are a smoker.  They are not alternative in that sense.  One does not drive the other from the field biologically.  In fact, all the evidence was to the contrary.  The one makes the other worse and vice versa when combined.

So that these were competing causes only in terms of legal argument.  They were never competing in reality and they were not alternative in reality.  If they had been competing or alternative in reality in nature so that if one, then not the others, we concede, without qualification, that the material shown by the respective relative risks would have made our job well nigh impossible.  I say “well nigh” because there might be facts outside the probabilistic reasoning.  It would be well nigh impossible for us to say if it was a choice between smoking and asbestos, well, you would prefer the asbestos.  That would be silly on the probabilistic material. 

There would need to be much more than that in order to have a hope.  That is only because they would be alternative, that is, truly mutually exclusive competing choices.  All the medical evidence about which all the experts were agreed was that far from being mutually exclusive alternatives or competing causes, these in a fatal way combined the very opposite.  So that the presence of one, in our submission, from the risk figures that the epidemiology shows in a population meant that the usual case – the usual case, and I use those words because of the legal question of probabilities – they were operating together because that is the only explanation for getting the greater than additive effect.  That is how you get a greater additive effect because they are operating together in the usual case.

HEYDON J:   Just because that is so in the usual case does not mean that this is the usual case.

MR WALKER:   I accept that wholeheartedly, with great respect, your Honour.

HEYDON J:   One has to form an actual belief, does one not, in the truth of a proposition.

MR WALKER:   I accept that too.

HEYDON J:   I just do not have any actual belief in it.

MR WALKER:   Your Honour, can I first try to persuade you by the usual case point.  If in the usual case exposure X leads to outcome Y, then in the absence of indicators either of a recognised or, in the particular case, demonstrated kind, removing the instant case from what I will call the ordinary normal or usual course, the plaintiff has, at least prima facie and probably to final determination, a more likely than not foundation for his or her position being the usual case, particularly when one is talking about medical science and human physiology. 

HEYDON J:   Can I just read out something that Chief Justice King of the Supreme Court of South Australia once said. 

the statistical fact that a particular proposition is true of the majority of persons –

perhaps the majority of members of the class –

cannot of itself amount to legal proof on the balance of probabilities that the proposition is true of any given individual.

MR WALKER:   I accept that entirely, your Honour.

HEYDON J:   Dr Leigh’s statement constantly assumes the conclusion it is trying to demonstrate. 

MR WALKER:   Your Honour, with respect, that is a stricture that I will not attempt entirely to avoid.  He is perhaps not alone in that, but that is not much comfort to me bearing in mind the reliance in the courts below on him.  He is not an outlier of course in this case.  He did not say things which were different from what anybody else said concerning what I am calling the extra danger of the combined entity.  Everybody agreed on that.  It is that which, with respect, is at the nub of this position.  I accept what Chief Justice King said though in a somewhat different context, if I recall, as I do very vaguely, that case.

HEYDON J:   I am sorry.  I should apologise to you and everyone else.  The reference is State Government Insurance Commissionv Laube (1984) 37 SASR 31 at pages 32 to 33.

MR WALKER:   Yes.  I recall generally the passage, your Honour, and I do not suggest that it is, as an observation, either inapplicable in court or dubious out of court.  In a sense, it is uttering a truism about the difference between the observation of a population and a decision about an individual.  If I may try and link this back to the questions that Justice Gummow has directed to me from time to time and also the proposition, the challenge that Justice Hayne has presented. 

Just as it is true, there are important unknowns and unknowables in a case such as the present and certainly in this case.  As I said to Justice Bell, you cannot look at the cancerous cells and say that is a tobacco outcome.  Equally, the nature of epidemiology means that you cannot say, ever, that the increased incidence or risk or chance of an outcome by reason of an exposure yielded by the numbers in study population means that an individual who comes outside the study population, an individual is more likely than not to be, if you like, representative of one or other of the groups.  It is not a possible form of reasoning.

The epidemiology, as I say, says something about the medical science or natural history.  It says, together with the laboratory work, look, this exposure is dangerous to the human organism.  In some cases, and if it were all cases we would have Cox postulates operating and it would be a dead easy case.  We do not have that in this kind of multifactorial multiple causation disease.  We do not have it.  What you can say is these exposures are dangerous.  We know that because of the pattern, if you like, of overrepresentation of persons thus exposed to this outcome. 

There are other things that can cause the same outcome and people who are exposed – some people who are exposed do not suffer the outcome.  That is material which logically can never permit, as Justice Heydon has, with great respect, properly pointed out, as a matter of logic.  That is either deduction, which it probably would need to be, or induction.  One could never say well, that means that this individual more likely than not.  It simply becomes, like the statement by the professor that exertion can cause, or trauma can cause, in Forst or Fernandez, the background against which the whole of the material is examined for the probabilities of whether the exposure of interest caused the outcome of interest.

HAYNE J:   Justice Kitto in Jones v Dunkel 101 CLR 305 described the process of inference in these terms:

One does not pass from the realm of conjecture into the realm of inference until some fact is found which positively suggests, that is to say provides a reason, special to the particular case under consideration, for thinking it likely that in that actual case a specific event happened or a specific state of affairs existed.

MR WALKER:   That is in line with what Justice Heydon – and I accept that ‑ ‑ ‑

HAYNE J:   Just so.  Now, is that the process of reasoning which you say was to be applied in this case?

MR WALKER:   It was, but whether it was or not, it had to be and it should be.

HAYNE J:   Thus, one passes from a finding of fact which provides a reason special to this particular case that a specific state of affairs existed, namely, that the deceased’s exposure to asbestos was a cause of his contraction of the disease.  What is the fact found, and it will presumably be a complex fact, which positively suggests, that is to say, provides a reason special to this case for arriving at that conclusion?

MR WALKER:   They are under three headings or perhaps they are three.  The first is the obvious one, see Forst’s Case, the danger eventuated in the right temporal sequence; exposure, then disease.  The second is shown partly by the forensic course to which I have referred.  It being well known that there are many other ways that one may come to suffer lung cancer than that for which the defendants were being blamed, including the tobacco, not that I blame for that, none of the experts ‑ ‑ ‑

GUMMOW J:   What do I write down for proposition two?

MR WALKER:   I am so sorry, I apologise, your Honour.

GUMMOW J:   I have got temporal sequence from number one.

MR WALKER:   Number two is elimination of true, that is my word, true competing causes.  Another way of putting it is no alternative explanation offered.  That comes from some discussion to which I was driven last night after Justice Gummow’s question to me in Wigmore, to which I will come in a moment just by way of a reference.

GUMMOW J:   Yes, and three?

MR WALKER:   Three is the observation of the young age of contraction in this individual indicative of the extra danger, the greater threat of the combined entity compared to the components separately, and that is Professor Musk in particular to which I will come.

It is our submission that that is a form of reasoning which is exactly the same as one will find in rather terser form in Forst’s Case, more elaborated in Fernandez, which, in our submission, is an important illustration.  If some of the arguments against us yesterday be correct, then it is inexplicable how this Court came to the conclusions it did in Fernandez’s Case.

KIEFEL J:   In Forst’s Case the temporal argument, I think – the reliance upon the temporal elements was upon a workman collapsing after he had strongly physically exerted himself and he collapsed from a heart attack, but even so, I think Justice Dixon said that there should have been greater reliance on medical explanations rather than assumptions which did not have a concrete factual basis.

MR WALKER:   I think all parties have given some references.  We have given some references.  I will just add one further reference apropos Justice Kiefel’s comment concerning Forst, a decision of the Full Federal Court and thus, I stress, not a case where there was any finding being made by the court about cause, just about the possibilities of having done so, in ATC v Barker (1990) 12 AAR 490 the bench comprised of Justices Davies, Gummow and Hill. Your Honours do not have, I think, this report. It is a reference that has occurred to us.

HEYDON J:   I think we do.

MR WALKER:   You do.  Thank you, your Honour.  I am sorry.  Yes, I have made it available.  You will find a passage at page 493 at about point 7 commencing and going over the page on to 494 down to about two‑thirds of the way.  I will not read any of it.  In our submission, it occurs to us that that is a useful indication of the continued appropriateness in legal reasoning about causation of the kind of approach that one sees taken, and I stress by the majority, in Forst.  Tubemakers of Australia v Fernandez (1976) 50 ALJR 720, if I could go to that and the reasons of Mr Justice Mason at the top of page 724, left‑hand column, you will see that the medical expert was doing what might be called do it yourself epidemiology. I am not suggesting it was a properly designed study, but that was the nature of the evidence in that case; case series I think they called it:

he had treated five cases of traumatic Dupuytren’s contracture and that cases of non‑traumatic Dupuytren’s contracture outnumbered cases of traumatic Dupuytren’s contracture by “something like 20 to one”.

There is a controversy about there being –

no causal connection between trauma and Dupuytren’s contracture, he disagreed . . . it more frequently appeared in persons who had not performed manual labour than in t hose who had performed that kind of work.

So this is a very strong case, this is a fortiori in terms of the kind of reasoning because it is all opposite here.  The combined entity produces lung cancer more frequently than tobacco or asbestos separately or simply additively.  The next paragraph says in relation to the propriety of that material for the factual reasoning, inferential in nature to be carried out by the jury, stands as strong support because of such a fortiori factual circumstances for our argument. 

T25/JLR

It is capable of being understood that trauma was a cause of the contracture.  By that means, the medical science, the natural history was such that Dupuytren’s contracture could be caused by, among other things, such trauma – that is what “a cause” means in that part – and that is was therefore a cause of the respondent’s disability and that would be because there was no other explanation offered.  That fits the kind of reasoning which very much more elaborately in the celebrated part of Wigmore – I have not reproduced this for your Honours and I do not wish to go to it in any detail at all – but your Honours will be familiar with the treatment by that author, including the revising editors who draw to attention controversy and consideration of Wigmore’s views in themselves.

HEYDON J:   These are the revising editors, McNaughton, people like that, not the latest people?

MR WALKER:   I am sorry, your Honour?

HEYDON J:   Not the latest people.  There is a thing called the new Wigmore.

MR WALKER:   Yes.

HEYDON J:   But it is not that?

MR WALKER:   No.  As your Honours appreciate, it is an accretive or palimpsest exercise; some of the originals survive, some of it survives with question marks and exclamation marks added, as it were, and some of it survives pristine.  But it remains, with respect, not least because it draws upon 19th century thinking which plainly can be seen to have had explicit influence on common law judgments since the 19th century under the heading “Modes of Inference and Types of Argument” and in, for example, the Tillers’ revision – and I think these numberings have been continued – it is 30 to 36 to which I draw attention and, in particular, for example, the kind of reasoning that is legitimate, we suggest, in this case might be seen under the discussion in Wigmore under the heading “Method of difference”.  This much has well and truly survived, namely ‑ ‑ ‑

GUMMOW J:   What paragraph is it in Wigmore?

MR WALKER:   In the Tillers’ revision, to which I had access, it is 33 and that happens to be volume 1A and which is headed “Practical requirements of inductive argument”.  Your Honours will recall the famous preference or collapsing by Wigmore of everything to inductive argument, that even the supposed syllogism by way of deduction involved induction for the major premise, but without going to that, which is the subject of considerable academic and professional argument, he refers here to “occasional subordinate tests; method of agreement and method of difference”.  Now, method of difference is very much in the heartland of what we submit is the legitimate use of epidemiological evidence and related materials, such as in this case, and the opening statement simply is:

The canon of the method of the difference is:  “If an instance in which the phenomenon under investigation occurs, and an instance in which it does not occur –

and the phenomenon here would be lung cancer –

have every circumstance in common save one, that one only occurring in the former –

and that circumstance would be exposure to tobacco and asbestos –

the circumstance in which alone the two instances differ is the effect, or the cause, or an indispensable part of the cause –

and that is an expression that certainly conveys material contribution when there are multiple factors at work –

of the phenomenon.

Now, as is well known there are ways of dealing with that which will then determine the admissibility of material marshalled for that purpose for that kind of reasoning and they include, in particular, alternative explanations so as to render not natural or more probable that for which the plaintiff contends.  That is why it is significant here that there is no reasonable explanation put forward for the suffering of the lung cancer, other than exposure to tobacco and asbestos.

Now, it might be said but the whole argument was whether this was really a tobacco case, not a tobacco and asbestos case.  But my point is this.  There was only one exposure.  It was to tobacco and asbestos and all the other many causes of lung cancer known to medical science or believed from medical science were eliminated by the joinder of issue and the content of expert evidence.

That then raised the question, well what does medical science say about the operation in fact in an individual of the asbestos when it is part of the combination tobacco and asbestos?  What the medical evidence said, in fact, was the usual case is that it will operate because that is why you get this near multiplicative outcome study in a population, wherein otherwise it could only be additive.

For those reasons as a step to creating that actual belief to which Justice Heydon, with respect, appropriately points for the discharge on the balance of probabilities of our burden of proof, it is a good and useful start for us to say Mr Cotton’s case presents consistently with – that is a good start – the usual case, tobacco and asbestos both having operated to produce lung cancer.  There is nothing put forward to remove him from the usual run of case, nothing, for example, studied in epidemiology as a special co‑variable or a different factor which might distinguish the matter, notwithstanding the eminence and comprehensiveness of their efforts of the experts on both sides.  The forensic contest, as it were, made its own universe of possibilities winnowing out or discarding, as I said to Justice Hayne.

Then we added, obviously enough – I mean we have to add and we make no apologies for adding the temporal sequence, we have to have that, it is in the nature of things.  Some people say that is enough, we had more than that because we had a disease known to follow from tobacco and asbestos exposure, that being known to operate, as we say, in such an extra dangerous fashion and we had his early onset of it.

Your Honours have been given something called our additional material which reproduces graphically an exhibit at tab 3 which was used to illustrate a point to which I will come in Professor Musk’s evidence.  One can see that at 42 he was in a class of considerably less than 10 in 100,000 concerning the outcomes of lung cancer.  So his was a rare matter, which Professor Musk regarded as a striking circumstance entirely indicative of the extra danger, as I have been putting it, in relation to the combined entity to which he was, in fact, exposed.

Could I take your Honours, please, in volume 1 of the appeal book to page 21 at about line 12:

What age was Mr Cotton when you saw him, professor?‑‑‑43.

I am sorry, I have said 42.

In terms of the potential cause or causes of his lung cancer, did you attribute any significance to that?‑‑‑Well, I thought this person is a young person who has developed cancer and I wonder what increased his risk ‑

What increased his risk -

so early in life.

That means, among other things obviously, over and above his smoking history.

If you have greater risks then it’s more likely you develop it earlier.

That is exactly what he had ‑ greater risks.  The greater risks come from the medical science natural history of the human body confronted or insulted by tobacco and asbestos.

For those reasons, in our submission, we come to the point where the legal argumentation involves this question.  Was tobacco really a competing explanation, an alternative cause to tobacco and asbestos?  The first thing to be noted is none of the experts on either side ever ventured the counterintuitive possibility that the influence of one or the other of these substances would protect from lung cancer by the other, or that if one caused then the other could not cause.  That is because they all joined in pointing out the extra danger of the combination.

Now, that really means that there was no competition between them as causes, there was simply this fallacious argument that because tobacco was predominant and greatly so, asbestos could not be regarded as more likely than not a material contributor, hence the attributable fraction manipulations. 

To complete the argument in relation to how legitimate inferential reasoning can be used, in our submission it sufficed only for us to note that because in the usual case they must be operating together, otherwise the figures would not be produced as they are for relative risk and because there is no alternative explanation or differentiating factor suggested by the medical, social or personal history for Mr Cotton and because of the early onset of a disease compared to what would happen with smoking, it was legitimate for the trial judge to find that more likely than not the asbestos contributed by its combination with tobacco to the lung cancer being contracted.

That is not the end of the case because we have to have successfully demonstrated that that contribution was material, a matter to which I need to turn.  Before going to that question of materiality, may I take your Honours in volume 1 to page 400.  This is in Professor Berry’s material that is called for the defendants.

KIEFEL J:   May I interrupt you just for this inquiry.  If you have the two - tobacco and asbestos interacting, do you need to consider materiality, if they are actually interacting?

MR WALKER:   In essence, no.  There may be a marginal case.  I have suggested using the crude language of multiplier and multiplicand in my written submission to continue this notion of multiplicative effect.  I have suggested that if a multiplier – treating it as the smaller of the two – was so small that it made virtually no difference, that that is classically the concern of the law not to find somebody liable to compensate.  That would not be material, so it is not quite enough for me to say, look they have operated together, there is the materiality ‑ ‑ ‑

KIEFEL J:   Yes, quite so.

MR WALKER:   In this case, yes.

KIEFEL J:   You do not have to show the asbestos as a sufficient cause, but you had to show it as a material cause?

MR WALKER:   Exactly.

KIEFEL J:   So your levels there may not have to be terribly high.

MR WALKER:   If it is 20 per cent attributable fraction, good, that is fine, it is operative.

KIEFEL J:   I follow that.  The question is whether you get to the interaction.

MR WALKER:   Exactly, and that is why, in trying to answer Justice Heydon’s challenge to me, I am bound to start with what the higher relative risk up and above additives for the combined entity says about what I am calling the usual case and what was it in the evidence considered as a whole with all the forensic testing available, what was it that removed this man from the usual case?  Nothing.  Then we had this extra thing.  What was the extra risk that caused him to get this so early?

It is for those reasons, in our submission, that at first instance this was an example of legitimate causal inferential reasoning entirely on all‑fours with the orthodox approach taken by this Court, and with great respect, done with real elaboration.  The dealing by the first instance judge with the attributable fraction material in particular, the paragraph, I think, is 374, that describes the outcome as enigmatic, comes about because – and one heard this in South Australia’s argument yesterday – the startling proposition appeared to be supported by the arithmetic manipulations that because when you multiply one fraction by another you will get a smaller fraction, that being a law of arithmetic, somehow the combined entity was less dangerous than either of the separate entities, and that was a nonsense, nobody was pronouncing that.

The reason for why that fallacy was introduced was because of the inappropriate use of attributable fraction for the completely specious proposition that that had to do with the chance that something had operated.  Attributable fraction takes as a premise it had operated and then is looking to what I have called relative potency and that is why the figures that Justice Kiefel asked me to consider at the foot of Professor Leigh’s report are not, in truth – although two per cent starts to make one feel a bit itchy as a plaintiff - in truth 20 per cent certainly is not a problem in terms of materiality.

To return to a question of Justice Kiefel yesterday concerning exposure data, I referred to a principle in our law of evidence concerning evaluating evidence by a number of features, including the capacity of parties to adduce it.  I should have added another matter to that which, in our submission, goes to this question of materiality and that is that the exposure in question could only be described by anecdotal – mostly by anecdotal references and we have given references to that in our written submissions.

May I, for clarity, make it clear, without taking your Honours, given the time, to it?  Where one will find this - in relation to the South Australian exposure between 1976 and 1978 you will find references in volume 3, page 1095, paragraphs 95 to 97 and 1097, paragraphs 99 to 100.  You will also find references at page 1096, paragraph 97 and to page 1108, paragraph 121 as well as references in paragraph 106.  The Millennium exposure in the same judgment in volume 3, paragraphs 144 to 154, particularly the conclusion in 154.  There are references in 156 to 170, 171 through to 236 in relation to the actual presence found of asbestos at Millennium.

Now, I should have added in answer to Justice Kiefel yesterday this.  There is an element of the same reasoning that underlies Armory v Delamirie that needs to be inserted into the evaluation of evidence concerning the significant importance of exposure to asbestos.  In 1976, as it happens, Professor Berry himself had published material concerning the so‑called multiplicative effect, in other words when you add asbestos to tobacco or tobacco to asbestos.  Many workmen smoke and many smokers are workmen.

Then he was publishing material in 1976 about that extra effect and one will find that, in particular, in volume 1, page 400 at the foot of the page about line 35.  He was:

part of a working party convened under the auspices of the World Health Organisation by the International Agency for Research into Cancer -0

I referred earlier to IARC –

issued a statement relating to the state‑of‑the‑art, as it were, knowledge regarding the risks of lung cancer –

et cetera.  He is shown the document and page 401, line 20 that remains his knowledge about state of the art back then.  Then at page 402 about line 30 you have the reference to the “multiplicative” effect that your Honours must be weary of hearing about.

So bearing in mind these are appellants who fought but lost on the issue of duty of care and negligence, when we come to the question of causation and the evidence about the importance of exposure to asbestos, these are people who continue to expose men to asbestos, notwithstanding the state of the art was as Professor Berry, one of their own witnesses shows, without monitoring the exposure and thus without any data by way of measurement. 

It would be contrary, in our submission, to a common law approach, both what I referred to yesterday and what one sees in Armory v Delamirie to hold in any way against the plaintiff the necessary inexactitude or impressionistic nature of the evidence very carefully considered by the trial judge supporting his findings about the considerable significance of the exposure to asbestos.  It is for those reasons, in our submission, that there are no weaknesses in the plaintiff’s case shown up by what I call the spurious precision of figurings based upon exposure data.  Rather, if anything, it is to the contrary. 

HEYDON J:   So the means of proving causation in a tort of strict liability are different from the means of proving causation in a tort based on fault like negligence, are they?

MR WALKER:   I think I said yesterday – I may have said yesterday, your Honour, that when - I am talking about causation is for negligence and Armory v Delamirie of course is a deliberate tort conversion.

HEYDON J:   Yes, and it seems to me in a totally different category from the carelessness of those who deal in or expose people to asbestos in 1976.

MR WALKER:   There can be no doubt that the abstraction of the chimney sweep’s diamond is completely different.  It is the principle that if involved in the wrongdoing is the explanation for the lack of detailed evidence, then that ought not to be held against the plaintiff.

HEYDON J:   It is not a question of holding it against the plaintiff, it is just that there is a shortage of evidence.  It is a problem for both sides.

MR WALKER:   If the shortage remained such a null, then it would of course redound to the disadvantage of the plaintiff.  But we had copious ‑ ‑ ‑

HEYDON J:   Is it sort of morally opprobrious to destroy one’s business records within a period of 32 years after the events they record?

MR WALKER:   Your Honour, there are no business records here about exposure or monitoring.  We do not have monitoring measurements.

HEYDON J:   I see.  You are working a great extension of Armory v Delamirie though.

MR WALKER:   Your Honour, I do not wish ‑ ‑ ‑

HEYDON J:   You are really just knocking out causation as a requirement. 

MR WALKER:   No, your Honour.

HEYDON J:   You are just saying there is a hole.  There would not have been a hole if they complied with our opinions on the law of tort, therefore we have proved our case.

MR WALKER:   No, your Honour, and I hope our argument is considerably different from that.  There was copious and detailed evidence about the fact that these men were exposed to asbestos, that is Mr Cotton and his workmates. 

HEYDON J:   You are really just trying to make our blood run cold and make our flesh creep.

MR WALKER:   No, your Honour.

HEYDON J:   I mean, you read us from Sir Anthony Mason describing what a jury might treat as a basis for leading a certain - well, we are now the jury and we are being made conscious of that by this submission.

MR WALKER:   Your Honours, examining the findings of tribunals of fact, that does not make you a jury but there are obvious parallels, however fleetingly, with the tasks in hand ‑ ‑ ‑

HEYDON J:   But there is no question of any court below us being in a superior position, is there?

MR WALKER:   No.

HEYDON J:   It is as if we are looking at it afresh for ourselves.

MR WALKER:   Yes.

HEYDON J:   That is what triers of fact do.

MR WALKER:   But asking the High Court question, what should the Court of Appeal have done?

HEYDON J:   I do not personally find it helpful in assessing causation to be constantly reminded of the moral wickedness, perhaps, in the defendants having exposed Mr Cotton and many other people to asbestos.

MR WALKER:   Your Honours, I do not think at any point I have made any statements about moral wickedness ‑ ‑ ‑

HEYDON J:   You are comparing it to Armory v Delamirie.

MR WALKER:   I am sorry, your Honour, for the purpose of showing that where the wrongdoing involves the loss of the material in question, that ought not to be held against the plaintiff.

HEYDON J:   It is not being held against the plaintiff.  It is just a problem for both sides.

MR WALKER:   Your Honour, ultimately yes, that is true, but we had enough material for the court below to find - indeed it is not seriously contended against us in these appeals that the evidence of exposure was evidence of exposure so slight it may be ignored.  The “so slight” question came about through this notion that if asbestos is minor or subsidiary in the combined entity, then it cannot by dint of some, we submit, legal fallacy, be held more likely than not to have been a material contributor.  We say that is a proposition that bespeaks its own error because it starts with the fact that it has contributed.  The only question then is materiality of the contribution, not whether it contributed, so ‑ ‑ ‑

KIEFEL J:   But in a way you are reversing the onus, are you not?

MR WALKER:   No.

KIEFEL J:   You are saying that the requirements for causation should be lowered.

MR WALKER:   No.

KIEFEL J:   Well, what are you saying we are supposed to draw from the fact that the insufficiency or the shortage of evidence should not be held against your client?  I am not quite sure what you are saying.

MR WALKER:   Your Honours, I have obscured a point unnecessarily.  My argument is that there was enough material on orthodox lines to discharge our burden of proof on the balance of probabilities on relevant facts.  One of the relevant facts was that there was an exposure to asbestos of a kind considerable enough to have produced a combined effect with tobacco of lung cancer in this man, that is, that notwithstanding, there were no measurements because there was no monitoring, matters that we say are tied up in the commission of the negligence and not due obviously to anything on the plaintiff’s part – notwithstanding that, there was enough of the anecdotal, descriptive or impressionistic material to justify the findings, and I stress none of the appellants really are intent to say “Look, there was only a tiny bit of asbestos”.  They do not say that.

KIEFEL J:   But you have a finding of breach of duty?

MR WALKER:   Yes, exactly.  I have over striven, I am sorry your Honours.  The causation question is to be addressed for the purposes in hand which is after duty found, after negligence found, did the negligence cause the outcome in question?  Because it is shaped by the purposes for which it is being asked, in our submission, it becomes legitimate if there be criticisms concerning inexactness of proof, to evaluate the evidence according, one, to the capacity of the parties to adduce it.  Clearly it is the defendants who can adduce measurements if there be any of asbestos.  Two, taking into account that the wrongdoing itself – this is not a moral question, this is an explanation historically of the paucity of material – that the wrongdoing itself may have involved that which produces the lack of exact data.  That is certainly true ‑ ‑ ‑

KIEFEL J:   But therein you have a difficulty which sets it apart from other cases where I think this argument has been raised in Canada.  Here you have two causes, so there is a potential “wrongdoing” by tobacco smoking.

MR WALKER:   Unquestionably, your Honour.  They are not competing causes though, without repeating myself.  The only competition in question is a legal competition.  They were never competing biologically.

KIEFEL J:   I am interrupting you, I realise, but would you mind reminding me, having applied the multiplicative effect, what figures were reached by Professor Berry.  I think he reworked Professor de Klerk’s figures.

MR WALKER:   There is an explanation.  I think these figures may be hypothetical figures ‑ ‑ ‑

KIEFEL J:   I am sure you will explain them to me, but perhaps if I could just have them.

MR WALKER:   They certainly hugely favour us, but I think you will find the figures that I think show Professor Berry more or less – I am not sure he is agreeing with, he is accepting the method of Professor de Klerk, is at volume 1 page 433.  I do not think this is his independent opinion.  He is just agreeing with the result.  It ends up on that page about line 15:

If I was doing this I would multiply the 1.3 –

that is the relative risk for asbestos –

by the 7.7 –

that is the relative risk for tobacco –

which would give me nine point something, I suppose, about 10.

I think it is actually 10.01 or something.  These are the figures that have been reproduced in Millennium’s written submissions and then taken up by us in our written submissions.  I think, yes, that is Professor Berry’s there, your Honours.  Then there is passage that commences at the foot of the next page 434 and goes on to the top of page 435 where there is an explanation.  I do stress, I think these figures might be hypothetical.  They are certainly figures we would like to use.  You see the rather larger numbers there.  It is just a function obviously of when you increase factors you increase the product.  On any view of it, as we have said in our written submissions, this is a difference which the law would not ignore.  It is a difference that matters.

KIEFEL J:   That is just a relative risk figure, is it not?

MR WALKER:   Yes.

GUMMOW J:   These were questions put by the judge, were they not?

MR WALKER:   Yes.

KIEFEL J:   No one ever reduced that to a probability figure?

MR WALKER:   No.  I may not be quite clear what your Honour means by probability figure.  In a sense, relative risks convey a probability calculation, that is, they are a record expressed as a ratio of comparative incidence in two groups.  That can be expressed in probability as a probabilistic calculation, yes.

KIEFEL J:   Yes, I follow.

MR WALKER:   Your Honours, then returning to the question of materiality, could I come directly to the passage in Bonnington v Wardlaw [1956] AC 613 which is under attack in this case. Your Honours’ attention has already been drawn to the statement of facts by Lord Reid commencing at page 614 and the second half of 615. There is a reference to the nature of the dust in terms of significance of quality between what I will call the guilty and non‑guilty sources in what was overall said to be a guilty atmosphere. I pick that expression up from the argument to which reference was made yesterday at page 617 by the Dean of the Faculty at about point 6 on that page which uses the expression “not negligible” or “inconsiderable” for the so-called guilty source.

On page 620 the statement of principle concerning what the plaintiff had to prove in accordance, we submit, with the unaltered position in this country at this date, namely, third line, that “such fault caused or materially contributed to his injury” and then there is a repetition of that at the foot of that paragraph at about point 5.  On page 621 there is a reference to the nature of the disease which may require a little bit of distinction from our case to which I will come after I have dealt with the authority.  There is a reference there to the:

pneumoconiosis is caused by a gradual accumulation . . . means, I think, that the disease is caused by the whole of the noxious material inhaled –

Whether or not that is contestable is a matter of medical science.  That is a factual premise upon which the legal reasoning then proceeds.  What I might call the attributable fraction fallacy is dismissed in different language in the succeeding sentences with the conclusion of his Lordship:

It appears to me that the source of his disease was the dust from both sources –

the source of the lung cancer here was the tobacco and asbestos –

and the real question is whether the dust from the swing grinders materially contributed to the disease.

The fact that they may have been subsidiary in terms of the quantity produced is obviously not to the point.  Then there is a statement which surely is correct, namely –

What is a material contribution must be a question of degree.

So far so good.  Then comes the impugned proposition –

A contribution which comes within the exception de minimis non curat lex is not material –

That must, of course, be true and accepted.  The question is whether that is the complete statement of what is not material.  Then his Lordship says –

any contribution which does not fall within that exception must be material.

Now, it is true that this is reasoning which lends itself to a form of parody, that is, what do I mean by “material”?  I mean something that is not immaterial.  One could only apologise if that is all you could ever say about what “material” meant.  In our submission. again you return to the nature of the task in hand.  Why are we asking the question about causation when the duty was imposed because of a risk when the negligence was found because of insufficient efforts to obviate or reduce that risk? 

In our submission it is appropriate to recognise that if the danger in hand is such that it appears that by reason of sequence, by reason of individuating matters – the man’s age in this case – more likely than not the asbestos contributed to the outcome.  Then one goes back to the question, informed by the nature of the duty and breach determinations, and asks, well, could anyone say this does not matter, that this is a contribution that made a difference about which the law does not care in the sense that it will not compensate a person for having suffered the outcome to which, as a premise of this argument, a contribution was made?

FRENCH CJ:   When you have got to the point of completing inference as to contribution, is that the end of the inferential process and is materiality simply a matter of a qualitative assessment or is there some further inference to be drawn about the nature or degree of the involvement of the asbestos and what is the basis for that in this case?

MR WALKER:   It must be the latter, I accept, which means I have to be able to answer the last of your Honour’s questions.  It must be the latter because, as we have said in our written submissions and I have repeated in address, of course there must be cases where accepting combined operation the amount or perhaps, depending on fibre types, the nature of the exposure to asbestos can be seen to have added such slight extra danger, such slight extra danger, that its effect in the combined entity really made no difference.  That is, of course, as Lord Reid said, a question of degree.  It does involve, as the Chief Justice has put to me, some further inferential reasoning in this case. 

That is why I have been perhaps as over sensitive as I have shown myself in relation to the exposure data, because your Honours will recall the exposure data produces from various experts an alarmingly wide range of so‑called attributable fractions and some of them so vanishingly small as the appellants are happy to attach to as obviously to bring me into the danger zone that, well, there has been a contribution but it has not been material.  In our submission, the facts rather, as found by the trial judge, are really very comfortably to the contrary of that as a matter of inference concerning the extent of that exposure.

HAYNE J:   Is the reasoning you would have us adopt on causation accurately captured by Professor Musk at line 33, page 41 of volume 1 in the last three questions and answers appearing on that page, but, in particular, the second‑last question?

MR WALKER:   No, is the answer.  That was a question directed to what I might call independently operating carcinogens and is not directed to the studied entity, tobacco and asbestos.  That is, there is epidemiology on smokers and asbestos.

HAYNE J:   Yes, I had read it with page 31, lines 18 to 22 as an explanation of the professor’s assertion of cause.  I had read it, correct me if you think I am wrong, I had read it as his assertion of cause explained by his answer at 41, line 33, if there are two carcinogens present do not discard either and that that is what he meant by cause.

MR WALKER:   No, but his reference to the studies, which in the intervening pages, are references to the observance of increased incidence in comparison groups that involve asbestos or smoking or smoking and asbestos, and so it is far more than – I cannot say this is no part, because this is a sworn answer, your Honour sees the content – it is far more than that being if there is an exposure then it must have been a cause.  But tobacco and asbestos is more than simply saying it is there; it must have been.  This after all is the man who refers to the extra risk involved by reason of age.  That is more than simply saying it was there.  That is drawing on the science that says, and that has been observed to be more dangerous even than the addition of the two separately.

Your Honours, when it comes to this sentence in Lord Reid’s speech, this case, in our submission, does not provide an occasion, that is it does not require as a necessity, examination as to whether the word “must” in the expression –

which does not fall within that exception must be material -

whether that is an overstatement or an overemphatic or just plain wrong, statement of flip‑flop reasoning.  We have offered some paraphrases of the word “material”, which like the word “reasonable” does not happily lend itself to paraphrase in a court of law, in paragraph 66 of our written submissions, and we have deliberately in those phrasings drawn on and tried to involve notions that recognise the purpose for which this causal inquiry is being made, namely to make a link appropriate for the purposes of awarding compensation to a person where there is a duty owed and there has been a breach of that duty.

There are other expressions in the speech to which I should draw attention though, apart from that impugned sentence.  In page 622, when it came to decide the case, and this of course, is not necessarily describing a minimum case necessary, but you will see that his Lordship in line 5 uses the expression “a substantial contribution”, but before, as I say, that cannot necessarily stand as the minimum required because about 10 lines further on, his Lordship refers to an unavoidable conclusion that –

the proportion which came from the swing grinders was not negligible ‑

and that is the way in which the matter ends at the end of his speech on page 623 about point 5 of the page, so that not negligible appears to be, in English, his Lordship’s rendering of anything not within the maxim, I think.

Lord Tucker certainly took the same approach, end of his Lordship’s first paragraph.  Lord Keith on page 626 importantly considers the very question which is raised by the argument of predominant contributor.  In this case he uses the word “main”, 626 about point 3 or thereabouts:

exposed much more immediately and in a much greater measure to silica dust released from these castings.

That is the so‑called innocent source –

I am prepared to agree, as did all the judges in the court below, that the main source of silica dust inhaled by the pursuer came from this operation, a cause for which it is agreed the defenders were in no way to blame.

So the case presented in a combined cause setting, admittedly the same kind of exposure, but there was the entity of the combination which Lord Reid said has to be treated as the source of the disease.  Lord Keith then refers, just above halfway, to “contributed materially”.  That is repeated just after halfway “materially contributed”.  Then about an inch further down –

Small though the contribution of pollution may be for which the defenders are to blame –

small did not deter his Lordship –

it was continuous over a long period.  In cumulo it must have been substantial –

and I draw that to attention –

though it might remain small in proportion.

That is our point about the asbestos, reading the findings about the asbestos.  This was substantial exposure.  Then at the foot of the page –

I think the natural inference is that had it not been for the cumulative effect –

In our case we say if it had not been for the tobacco and asbestos –

the pursuer would not have developed pneumoconiosis when he did and might not have developed it at all.  The inference, of course, would have been different if it could have been shown that the pursuer could not have inhaled any particles given off from the swing grinding operations –

That is in accordance with the way we have argued the case –

or that the particles negligently released from the swing grinding operations were released at intervals so infrequent, or in quantities so insignificant, even if taken cumulatively, as to make it unreasonable to regard them as a material contributing cause –

That is also in accordance with what we have been putting.  Now, then comes the sentence which is awkward for me because I am not embracing a reversal of onus.  His Lordship does say that –

But that, in my opinion, the defenders are unable to show. 

I do not submit that that is part of the law in this country –

On the whole evidence, I consider that the pursuer has discharged the onus –

that is happier for me –

that is upon him of showing that the defenders’ fault was a –

and I stress the indefinite article –

material contributing cause of his illness.

In our submission, your Honours, the literal and legal meaning of the expression “not negligible” is something that almost assumes its own conclusion.  It means something that cannot be said you do not care, because care in this case, whether you care about something is the test as to whether it would be counted causal or not, it is an entirely circular operation.  Perhaps the only guide that ought to be pronounced is that it is a matter of degree for the reasons particularly emerging from Lord Keith’s discussion of the evidence in that case.

GUMMOW J:   I think Lord Keith may be talking about the defendants being unable to show something in terms of forensic onus.

MR WALKER:   Evidentiary burden in the sense, perhaps - in the same sense that this Court has talked about in Watts v Rake and Purkess v Crittenden - related, not exactly the same.  But it could not be right if it was intended to be a legal shift.  At most it would be an evidential shift.  So the disentangling if it is proved that you have contributed, disentangling to show that your contribution was not material is perhaps a mere evidentiary burden, which is in accordance with orthodoxy in this Court.  See Watts v Rake.

Your Honours, I said I would deal with the difficulty presented by the word “cumulatively” in the majority reasons and this relates as well to the possible difference between some diseases and others.  I apologise, there is an over‑abundance of supposedly specialised nomenclature in this case and it can be confused, as it was in this case, as noted by the Chief Justice concerning the trial judge’s use of the words “divisible” and “indivisible” which were neatly reversed as to their conventional usage by the trial judge without altering the cogency of his reasoning.

“Indivisible” relevantly simply means that the severity of the disease – in this case the lung cancer – is not going to be increased by further or increased dose of the carcinogen.  On the other hand, the risk of getting the cancer is in direct proportion to the amount of the carcinogen to which you are exposed on a fairly obvious probabilistic basis, I suppose, in terms of occasions of risk presented.

Your Honours are spared mercifully the casuistry of so‑called single fibre theories and the like which bedevil this area of litigation.  Divisible injuries, on the other hand, are a bit like industrial deafness.  You may lose the enjoyment of the brass band after some excessive noise, but you may become stone deaf if it continues longer.  It is progressive in that sense.  It exacerbates the actual condition.  Those are the cases where, of course, people who materially contribute may say, “I am liable only for that part or that part of the disease to which I contributed.  I was responsible for the noise that meant you could no longer hear the cornet solo, but I certainly was not on the scene and was not your employer when you were rendered stone deaf by further”.

So those are the differences according to the nature of the factual inquiry, indivisible and divisible diseases.  None of that mattered in this case.  “Cumulative”, of course, is a very unfortunate word because it could describe the cumulation of hammer blows that make people from anything from hard to hearing through to stone deaf.  But that is not how their Honours were using it as can be seen from the passages in question.

Could I take you first to paragraph 311 in volume 4, page 1506.  The, as it were, self‑contained dictionary there is working cumulative, operating interdependently to produce the injury or disease, by contrast, the alternative exemplified by that considered in Wilsher.  One can see also in paragraph 315 the same lexicon by their Honours, “inter-dependent (cumulative)”, and the same can be seen on the next page, 1508, in paragraph 319 in line 23 “operate inter-dependently and thus cumulatively”, et cetera.  It stands in short for what has also been described as synergistically or multiplicatively.

Your Honours, it occurs to us I should have added another reference as well as to ATC v Barker concerning Forst and Fernandez.  I do not wish to take you to it.  I do not think anyone has given it to you.  It is in Fernandez (1975) 2 NSWLR 190 in the Court of Appeal, Mr Justice Glass, at page 197. I do not suggest it adds anything different but, with respect, from that source it is worthy of attention. Can I come now to an argument which was tagged, and this was not the whole of the argument, of course, by Mr Watson, by way of a protest against being rendered liable vicariously, that species of vicarious liability, for the exposures of others. This was, as it were, using resentments among the appellants against us, the first respondent.

BELL J:   Can I just ask before you move to that, in the reasons of the Chief Justice at page 1474, paragraph 208, he says that:

Dr Leigh’s process of reasoning is contrary to the position of all the other experts, whose evidence was to the effect that, within a group of lung cancer sufferers exposed to both carcinogens, there will be some who would have contracted the disease irrespective of their exposure.

Is that just a reference back to the modelling?

MR WALKER:   Yes, that is all it is.

BELL J:   There was no ‑ ‑ ‑

MR WALKER:   There is no medical evidence, there is no biological evidence.  I am going to come to the question of grouping, both for that passage and another passage in the Chief Justice’s argument.  The grouping argument, in short, is completely fallacious, as can be demonstrated by the conclusion to which it tends, which in short in this.  You start with the premise that there are people in groups and you end up with a conclusion that they are all in one group, which is absurd.  No, that notion of it being common ground that within a group, et cetera, there are, no one ever said that that was a tenet of medical science. 

It was only a question of logic designed, as I tried to point out in answers to some of Justice Kiefel’s questions this morning, to deal with the fact that in the absence of knowledge, who knows whether, et cetera.  That is why we look to what the population studies show and apparently, accepting as a matter of logic as one must from our ignorance, of any one person with lung cancer who did smoke and had asbestos, of course it is possible, look at the figures themselves, that they did not get it on account of that exposure.  Of course that is possible.  That must be so, because it is not like enough of a bacillus and a disease, it is not like infectious studies, Cox postulates, where things follow, you can have the exposure and not get it.

At that point perhaps I should add to the digression.  At one stage my learned friend, Mr Jackson, said of smoking - and I apologise, I do not have it verbatim – in effect, “If you smoke you are probably going to or certainly going to get lung cancer”.  Happily or unhappily, depending upon one’s view about divine retribution, that is not true, and was not regarded as true by the expert whose evidence was cited by my learned friend to that effect.

The evidence that my learned friend went to is to be found on page 14 of volume 1 of the appeal book, where, with respect, correctly and dramatically, statements are made by Professor Musk to the judge which have to do with what happens if you wait long enough in relation to risks.  His saying is:

it will get you –

at line 15.  In fact, however, we do not all live sufficiently long to die from all the risks, slight or great, of our conduct, and that is why on page 13, when actually describing what is actually observed concerning smokers, Professor Musk says this:

Do you have an estimate of the number of heavy smokers who might contract lung cancer from cigarette smoking? ‑ ‑ ‑It’d be only an estimate.  The average regular smoker has a 50 per cent change of dying from a smoking‑related disease of one sort or another –

and they certainly include more than lung cancer –

and lung cancer’s high on that list.  If you mean by “heavy” more than about 30 a day –

Mr Cotton was 15 per day –

I’d say, without having the data to look at, that he’d have a risk of dying of lung cancer of about 5 per cent –

So whether public health authorities like it or not, they are not able to say, “If you smoke 15 a day or 30 a day, you will die of lung cancer, that is, more likely than not you will get lung cancer”.

GUMMOW J:   Wait a minute, there are two steps to it.  You will get, or you will die?

MR WALKER:   If you get it, you are likely to die, so ‑ ‑ ‑

HEYDON J:   There is a slight problem in what he says.  If you smoke 30 cigarettes today, you do not really have any chance of getting lung cancer at all.

MR WALKER:   Not a measurable one, no, your Honour.

HEYDON J:   Your likelihood of getting it depends on how many years you do it for.  What does he have in mind?  Was he talking about Mr Cotton, his length or ‑ ‑ ‑

MR WALKER:   No, your Honour, he is talking very generalised and very sketchy about tobacco epidemiology which could fill even this room, and with respect, of course, as Justice Heydon has pointed out, it has to do with measures which, I think, go by the wonderful expression “pack‑years”, which have to do with estimated daily consumption, apparently, and as Mr Jackson ‑ ‑ ‑

HEYDON J:   How many pack‑years does he have in mind here?

MR WALKER:   I have no idea, it must be over something that makes sense of mortality, and we know from the age‑related mortality that that cuts in after quite some years.  My point is this.  You do not start with the proposition that if you smoke the relevant number of pack‑years, which the evidence did not yield because this was never controversial, you will – that is, you more likely than not will get lung cancer.  All of them are chances.  It is the increased danger of getting lung cancer which leads to the relative risk of 7.7 that was used in the figures that have been adopted for argument in relation to smoking, compared to just over 10 for smoking and asbestos.

GUMMOW J:   Mr Walker, in Forst, which you took us to before, 64 CLR at 567, Justice Starke who was not a person loose with words expressed his conclusion there in the last sentence:

All this satisfies me, as it satisfied the Supreme Court, that the functional disturbance occasioned by the work of the deceased –

who had gone out on the crane and had a heart attack –

was intimately connected with and contributed to the –

condition that killed him.  Is that enough for you for what you say is the product of the inference?

MR WALKER:   Yes.  Everything combines to say ‑ ‑ ‑

GUMMOW J:   I do not know why we get obsessed with Bonnington when we have Sir Hayden Starke, frankly.

MR WALKER:   Your Honours, I think I can escape that stricture.  We have put this to the forefront in our written submissions and I think we have done it in our address.  We say what happened in this case was orthodox Australian law.  We were not trying to jump a gap.  If there is a gap that we could not step over then we fail for the reasons Justice Heydon has pointed out but we were not trying anything illegitimate or outside legal orthodoxy.

HAYNE J:   Does the statutory context enforced, in particular the expression of the question in the last three lines of 539, matter at all?

MR WALKER:   To our argument I think not for the reason that, one, material contribution is the law on what we need to show on the balance of probabilities and, two, materiality is a matter of degree.  Now, it may be more than a matter of degree but it is at least and almost certainly, ultimately, completely a matter of degree.  For those reasons, the statutory setting in which the question was whether it had contributed in any material degree to the condition is one that renders this on all‑fours for our common law purpose, yes.

Now, can I go to the question of so‑called vicarious liability.  If the lung cancer was such that its severity, whether it be fatal or not, for example, or how gruesomely fatal, et cetera, could be separated or divided, segmented, then of course it would be wrong in law for one tortfeasor to be liable for more than the damage to which it had materially contributed.  Lung cancer was not one of those segmentable outcomes.  It was lung cancer or nothing and once it was lung cancer, there it was, that is, in relation to the exposures. 

Hitherto, that is, until the argument in this case, it has not been doubted for over a century that a person proved to have materially contributed by negligence to damage is liable for the whole of the damages to be assessed to compensate for that damage.  That is why the common law doctrine of contributory negligence, the common law aversion to contribution between tortfeasors and then the statutory alteration, reversal to a degree, of both of those positions plays such an important part in actual litigation in negligence in this country. 

This is a common law question and it falls to be determined against the background made obvious by (a) the common law tradition and (b) the fact of legislative alteration of it, that at common law it does not avail any material contributor to say, “But I am only a subsidiary or minor contributor.  You are suing me because I have got money.  Why did you not sue the person more to blame who has no money”, to which normally a plaintiff and a plaintiff’s solicitor has a ready answer.

Mr Jackson referred, with respect, subtly to these considerations at the end of his address yesterday.  There is no call in any of the authorities in this Court to put any pressure on the way in which one would reason factually about material contribution by reference to the fact that upon it being found, liability for the whole of the loss will descend upon that defendant.  In other words, there has never been any statement suggesting that some perception of unfairness, being responsible for other people’s wrongs should intervene to affect the way in which one factually reasons about whether there has been material contribution.  In our submission, it would be a misstep for this Court to travel any way at all in that direction.

Suggestions that one finds in academic commentators, in particular upon both Canadian and English authorities about so‑called better ways being to allocate or segment liability, have to be understood as being, in our submission, not usefully expressed at levels of abstraction or generality.  Of course, close attention to what the damage in question is will mean that in some cases of so‑called divisible disease, for example, for the reasons I put there will be segmentation and if you like apportionment of damage, but not otherwise and, in our submission, the tradition in this country is that that must be left to parliaments to achieve and it has notoriously been achieved in this country in some jurisdictions, allocation of that kind.

It is for those reasons, in our submission, that one can put to one side a complaint, an appeal to some sense of unfairness that there has been a form of vicarious liability.

FRENCH CJ:   Mr Walker, that might be a convenient moment, but can you give us an indication of how much longer you expect to be?

MR WALKER:   I think 15 to 20 minutes, your Honours.

FRENCH CJ:   That will allow us comfortably to complete the balance?

MR WATSON:   Certainly, your Honour.

FRENCH CJ:   Yes, all right we will adjourn until 2.00 pm.

AT 12.46 PM LUNCHEON ADJOURNMENT

UPON RESUMING AT 2.01 PM:

FRENCH CJ:   Yes, Mr Walker.

MR WALKER:   Your Honours, next may I come to the intervening cause argument that was particularly presented by my friend, Mr Watson.  In our submission, it ought to be rejected because in reality it amounts to this.  The tobacco smoking was a predominant or the predominant contribution to the carcinogens which produced the lung cancer.  Without reference to any medical evidence that would support this and, indeed, contrary to the material I relied upon myself this morning, the next step is taken that if that were removed, he would not have got lung cancer, something that we do not know and something which is in abstract belied by the sufficiency of both asbestos and tobacco to cause the lung cancer, but, in any event, uses the predominancy of the tobacco to make it an intervening cause, that is, relevantly in law the only or sole cause to which responsibility may be sheeted home.

That, in our submission, commits the fallacy of searching for sole cause where there is multiple cause.  Multiple cause involves, as the premise of the expression shows, that more than one factor has contributed causally to the outcome.  The predominance of one or other among a number of multiple causes provides no warrant for, is not an occasion for, searching for that which would contradict the notion of multiple cause, namely, a sole legal cause.

The feeling in relation to intervening, just like the feeling in relation to being responsible for what other people have caused, is relieved, we submit, at common law by contributory negligence, particularly in a case like this where the so-called intervening or predominant cause was as a result of contributory negligence and would have been a co‑total defence, of course, at common law, relieved by common form legislative provision so as to permit apportionment such as occurred in this case.  That provides no justification whatever and is the most unsafe background against which for the common law to take a further step and to say that a predominant cause among multiple causes should be treated as sole for the purpose of being an intervening cause breaking a chain.

The next point I wish to go to concerns what we would call the “notional grouping” approach, used probabilistically to achieve the conclusion in the Chief Justice’s reasons in the Court of Appeal, that on the balance of probabilities the attribution of a causal contribution to asbestos in this man’s case could not be made out.  It comes about by a passage – an extended passage – of which I will only be reading or taking your Honours to a very few pieces, commencing in volume 4 of the appeal book 1468, paragraph 195.  But can I quickly skip some passages before I come to the relevant central portion?  At 197 your Honours will see the way the Chief Justice, with respect, appropriately noted the so‑called “multiplicative” or “synergistic effect”, with references from across the parties.

On page 1470, paragraph 201 there is the indivisible disease proposition noted by his Honour and then there enter what I am calling notional groups in that paragraph.  There is no medical science that says of those with lung cancer, having been exposed to the combination, this person has a cancer due to just one of those exposures, this person with just the other and this person with the combination.  It is a habit of thought used for attributable fraction reasoning, it is a notion.  One may think about the group which indifferently appears with lung cancer, having had the combined exposure as if they were grouped for the purposes of argument about, for example, attributable fraction.  But one is not describing anything that has any real biological or physiological corresponding phenomena.

Having set up these notional groups in the way that the biostatisticians and mathematicians do, at page 1472, paragraph 205 the notion of potency and grouping is continued and then the critical paragraphs are paragraphs 206 and 207.  His Honour refers - at about line 43 he says, “within that group there will be some”.  Now, this is a purely notional proposition for the purposes of argument.  No one says that has anything to do with physical fact or medical science.

The group in question after all is the group that produces the increased incidence over and above the mere additive effect of the two of the combined carcinogens.  That one is searching in this exercise for something which is beside the point legally can be seen by the end of paragraph 206, page 1473, line 5 where the exercise in question is as to whether something can be said to be the “sole material cause”.  In our submission this is already taking a logical misstep when one has putatively multiple causes.

In paragraph 207, finally, the numbers are done depending upon exposure levels, as his Honour appropriately points out, the numbers are done so as to produce at line 25 a reference to what his Honour calls the “largest cohort”.  That arises with what is called – the last two lines of that paragraph:

the predominant carcinogen, irrespective of their minor exposure to the other carcinogen. 

Again, this is not physiology or carcinogenesis in any biological sense which is being talking about.  This is attributable fraction thinking.  If, as we have tried to persuade your Honours, attributable fraction thinking starts with the premise, is not aimed at the premise, starts with the premise of all contributing, then this has nothing to do with the inquiry, did it contribute in this case.  But there is another reason why this kind of reasoning ought to be dismissed because it has the effect, inexorably by the supposed logic of this paragraph, that every single plaintiff on probabilities will always be treated as if more likely than not they would belong in what is called the largest cohort. 

So you start an argument by saying let us posit three groups, that if there is a predominant contributor, that will always produce the largest cohort or subgroup and therefore every single plaintiff probabilistically will fail to make out a case that, as it were, required membership of a smaller group.  That, in our submission, cannot possibly be a common law approach to probabilistic reasoning when the so-called small groups derive from an observation in medical science backed up in the laboratory and by epidemiological studies that there are people who get their lung cancer after such a combined exposure. 

It is reminiscent of the spurious need to have a relative risk greater than two which is found peppered throughout American academic literature on this subject and was, up to and including the Court of Appeal in these proceedings, persisted in as an argument on behalf of the appellants.  We have made that observation in our written submissions and we have provided in the booklet of additional material the written submissions and transcript in which, through my learned friend, Mr Watson, who then appeared for all the present appellants, that position was being put. 

That is an argument which says, notwithstanding the epidemiology and the lab science makes out that there is a causal effect of an exposure, unless the relative risk is more than two, you will always be able to say in a notional grouping of the numbers that produced that ratio, the group that does not fall within the so-called excess is always bigger than the so-called excess group and therefore every plaintiff fails.  So again, you start with the proposition some people get lung cancer because of this, but no plaintiff will ever be able to show that.  The relative risk greater than two fallacy is not persisted in this Court, but, in our submission, it is the cousin, it is germane to the fallacy that underlies the Chief Justice’s approach in paragraphs 206 and 207.

HAYNE J:   You say that the reasoning is fallacious.  What is the proper chain of reasoning, step by step, by which you proceed from observations about populations to a conclusion in the singular case with which you are dealing?  You identified earlier, in answer to that question, three considerations:  temporal, elimination of true competing causes and young age of contraction.

MR WALKER:   Your Honour may recall with the second I said “or alternative explanations”, which is much the same.

HAYNE J:   Yes.

MR WALKER:   I do not wish to add to that.  The next topic of ‑ ‑ ‑

HAYNE J:   Because the fallacy to which you point is said to be demonstrated by moving from the population to the individual case back to population by saying all plaintiffs must fail.

MR WALKER:   That is right and it is saying of the person for whom risk or chance is no longer the question, risk or chance in a population is why medical science says this is dangerous stuff.  But then you come to the person for whom risk or chance is no longer the point and you say, in the case of the relative risk needs to be greater than two point, no plaintiff ever succeeds.  We are happy to accept that this does cause it, but you will never show more likely than not.

CRENNAN J:   If there is a risk that all plaintiffs fail, applying an orthodox approach to causation, from what you have said so far and in particular from what you said at the outset, you are not offering us some alternative legal path, having regard to the fact that we know that in the cohort that has dual exposure, asbestos will be implicated in the lung cancer of some of them.

MR WALKER:   That is all I need, your Honour.  May I say this about the way your Honour started the question.  We are not saying that all plaintiffs will fail in an orthodox legal causation test, far from it.  We say that it is wrong to use the notional grouping of people to produce an excess that shows the causative effect of an exposure from population studies, the method of difference that Wigmore talks about, it is a mistake to use that at that later stage.  The stage we have reached is there is a contribution by all the factors in a multiple causation case.  Is it material?  That is the real question here. 

We do not need to propose anything different.  I hope I have made clear that we say that what was done and what needs to have been done was completely orthodox in accordance with authority, and I stress the spectre of all plaintiffs failing that I have raised does not come about because of orthodox legal reasoning.  It comes about because it is an inappropriate application of a chance or risk question at a point after somebody has suffered the disease.  There is no risk or chance of suffering the disease then.  You then ask, more likely than not, was the exposure in question which these risk or chance calculations or observations show can cause, more likely than not did it cause in his or her case?  If yes to that, but only because it was a factor among others, was its contribution material?  That is, in our submission, entirely orthodox.

HAYNE J:   But there is a significant intermediate question, is there not, presented by the passage from observation of incidence, which is the population study, to attribution of legal responsibility for the particular occurrence.

MR WALKER:   I think, your Honour, at more than one step.  I entirely accept that.  I think in our written submissions and address I have supplied them.  Yes.  The notion of leaping – and it would be a leap – from epidemiology to legal liability is, in our submission, impossible unless – and I have never seen this – the epidemiology amounted to 100 per cent risk, where of course it would.  You are not talking about multifactorial or mysterious processes then.  Could I then move to the “but for” orthodoxy and to at page 1506, paragraph 309 of the reasons in the majority to which reference was made in my opening.

It is true, and one would find it peppered, for example, throughout Hart and Honoré and other areas, it is true that where one posits multiple causation and severally sufficient factors, it has often been said sine qua non “but for” does not apply.  With respect, that is an ellipsis, because all it is really saying is that it does not apply to each of them severally.  At a moment’s thought, linguistic rather than philosophical, to say why that must be so, if you have more than one sufficient factor operating at the same time, then by definition from the word “sufficient” neither can be said to satisfy sine qua non.  The other is sufficient therefore, et cetera.

The law long ago said, well, that is just a ridiculous way for defendants to point fingers at each of and all to escape, but that does not involve any exception or distortion of the necessity nonetheless for the basal propositions of justice involved in a negligence action that there be the capacity to say “but for” as a negative criterion, as a screen.  It is but for the causes which operated would the damage have occurred.  That has to be answered, but for it would not have occurred.  Then one says, of the sufficient causes severally, asking the question appropriate to each defendant or to an absent person if a defendant is blaming an absent person, was the contribution by the sufficient cause for which the defendant is liable material?

If it is truly sufficient, and I stress, if it is truly sufficient then that question will answer itself.  It would be very difficult to see why a sufficient concurrent cause will not by definition be material.  We are close to that in this case, bearing in mind what the medical science says about asbestos, but I accept that the numbers do require to be done in particular cases as the experts in our submissions have pointed out.

FRENCH CJ:   Does an acceleration by – let us suppose asbestos accelerates a disease process initiated by tobacco.

MR WALKER:   Or the other way around.

FRENCH CJ:   Or the other way around.  Let us just take my first example.  Can you apply the - does the asbestos acceleration of something which was happening in any event by reason of tobacco exposure pass the “but for” test?

MR WALKER:   I am not sure.  It depends upon what acceleration means.  If acceleration means bringing forward the time ‑ ‑ ‑

FRENCH CJ:   Let us say the promoting phase.

MR WALKER:   “Acceleration” may not be the right word for promoting ‑ ‑ ‑

FRENCH CJ:   I see what you mean, yes.

MR WALKER:   If it means bringing forward in time something which was going to happen, which certainly was going to happen then questions arise as to whether dying earlier is compensable and usually the common law answer to that is yes and certainly the survivors who have actions would say yes.  Sometimes, however, the word “acceleration” is used, as it might perhaps apply in this case, to refer to something happening at a time which is earlier than might be expected if the putative or impugned factor was not at work.

That certainly would result in but for, that is, this disease phenomenon, when it occurred, would not have happened but for the combination of those carcinogens and if this disease phenomenon suffered when it was is itself compensable, it is legal damage as it is, then the “but for” test has been supplied.  So in paragraph 309, with respect to their Honours, there is support to be found in the literature for what is said about the “but for” test not applying to multiple sufficient causes but only if you understand that as meaning to each of them, in which case the proposition is of course axiomatically true.  It comes from the word “sufficient”.

The sentence that precedes that is one that in our submission goes further than is necessary.  Perhaps it should be understood in light of the succeeding sentence.  It suffices to say that for the reasons we put yesterday “but for” does have to be satisfied and is satisfied where there are multiple factors at work by asking the question about the multiple factors.  Then as to the factor for which an attempt is being made to hold a particular defendant liable the question is, having contributed, did it contribute materially?

CRENNAN J:   I take it there is nothing in any relevant civil liability statutes that eases your client’s burden of proof?

MR WALKER:   I think it is fair to say that there is nothing any Civil Liability Act provision that eases anything for any plaintiff, your Honour.

HEYDON J:   What about section 5D of the New South Wales Act?

MR WALKER:   I apologise for my facetiousness.  No, there is nothing that eases the way in relation to either material contribution or multiple factors.

CRENNAN J:   I had in mind a cognate to 5D of the Civil Liability Act (NSW) – I think it is 5D – raising an exception in relation to the “but for” test.

MR WALKER:   I do not think that will ease our way though, because we still have to prove on the balance of probabilities that the asbestos exposure more likely than not materially contributed.

CRENNAN J:   I just wanted to check whether there was anything that was relevant.

MR WALKER:   Thank you, your Honour.  There are two ways of answering it.  No, there is nothing that affects the position we are in, two, there is certainly of course nothing in it that could have any effect on common law doctrine obviously.

GUMMOW J:   It would be a question for the South Australian statute, would it not?

MR WALKER:   Yes, your Honour.

CRENNAN J:   Which is quite an old statute, I think.

FRENCH CJ:   A second exposure was in Western Australia, was it not? 

MR WALKER:   There are two jurisdictions in question, yes.

GUMMOW J:   But the timing is anterior to the statute regime, is it not?

MR WALKER:   Yes.  So it does not affect our position at all.  I think Justice Crennan’s question may have been more conceptually rather than about my plaintiff.  For my plaintiff, no, it does not make any difference.

CRENNAN J:   I have just got in mind that there have been developments elsewhere in relation to situations which are not dissimilar, where suggestions have been made about, as you put it in your opening, circumventing the “but for” ruling, a context like this one, but I think at the outset you said very explicitly you are not pursuing any of those paths.

MR WALKER:   No, and I stress, we would certainly not, in any event, attempt an argument that says that anything in a Civil Liability Act can be used to shape or influence the way the common law should be and there are a number of obvious reasons for that I do not need to develop.  The answer has to be, to Justice Crennan’s question, no, it does not affect this case and, no, it does not affect the doctrine for which I am arguing in this case, but, as Justice Crennan correctly points out, in any event, my stance is that “but

for” should not be discarded, it is necessary, it has to be asked about the correct thing, and in this case it is the thing that did operate or was there, namely, the combined exposure.  What he was exposed to was the combination.

A number of your Honours have asked my friends, given flaws in the Court of Appeal expression of reasons, what would one be left with in relation to the first instance judgment.  I do not wish to repeat what is already sufficiently in written submissions, but by way, as it were, of convenient collection of matters which, in our submission, show correct questions being asked by his Honour in an orthodox fashion, legitimate inferential reasoning from the epidemiological and related evidence being engaged in can be seen in the conclusions to which I will not go, but give you these references instead.  Volume 3 of the appeal book, pages 1274 to 1284 under the heading “Further conclusions”, and then the conclusions of course in the same volume, pages 1322 to 1347.  Those, in our submissions, are correct and appropriately expressed forms of common law reasoning to factual causation in this case.  May it please the Court.

FRENCH CJ:   Thank you, Mr Walker.  Yes, Mr Watson.

MR WATSON:   Your Honours, in reply I just wanted to offer some assistance in answering the question by Justice Kiefel regarding the evidence of Professor Berry about the attribution to the various matters.  If your Honours were able to get access to the appellant’s submissions in the Amaca appeal – Justice Kiefel, we have set these out in paragraphs 46 and following.  If I could just explain what they do, it includes Professor de Klerk as well as Professor Berry.

In paragraph 46, we have set out what was in Professor de Klerk’s report.  Professor de Klerk having made the calculations based upon assumptions that the risk from smoking was 7.7 whereas in truth it was 15 and the risk from asbestos was 1.3.  I will come back to how much that risk was, and there your Honours can see how that was apportioned by Professor de Klerk.  That is incidentally, your Honours, where the figure of 23 per cent came from which figures in the plaintiff’s submissions, but if one adds B and C together, that is where they get their 23 per cent.

Your Honours, in paragraph 47 – I have checked incidentally and subject to one matter I have checked these figures and footnote references, these come straight from the reports, your Honours.  In paragraph 47, we set out what Professor Berry had to say, and his assumptions, which were wrong in respect of smoking, but were very close to accurate in respect of asbestos.  With the asbestos reduced, the factors come down so that only 14 per cent is attributable to asbestos alone or in combination with smoking.

Your Honours, may I say this.  Both of those calculations are themselves in favour of the plaintiff because they underestimate the effect of smoking.  The trial judge’s finding was a risk of 15, and your Honours can see that each of Professor Berry and Professor de Klerk used lower numbers.  We also say that those calculations overestimate asbestos.  I will not labour it, but as your Honours know, we submit that the South Australian exposure only gave rise to a risk of 1.03 to 1.08 and in paragraph 49 we have set out the detail of that and the evidence that we rely upon in respect of it. 

Your Honours, no expert gave a calculation based on precisely the correct figures, but in paragraph 50 we get one of Professor Berry’s calculations based upon a relative risk from smoking of 15, which was right, and a relative risk from asbestos of 1.01, which, as your Honours can see, is too low.  On that calculation, asbestos comes down to one per cent.  Then in paragraph 51 I set out some matters which related to that evidence I read to your Honours yesterday about the 100 to one chance and in that instance Professor Berry was actually using a relative risk due to smoking of 10, which is too low, but a relative risk of asbestos of 1.08, which is spot on at the top end of the range.  Professor Berry then said it was a ratio of 100 to one.  May I correct one matter in footnote 22.  The pages should read 391 to 392 and there should also be a reference to page 395.  Subject to your Honours’ questions, that is all I had intended to say in reply.

FRENCH CJ:   Yes, thank you, Mr Watson.  Yes, Mr Abbott.

MR ABBOTT:   If the Court pleases, I would like to briefly make three points.  First is a matter your Honour Justice Kiefel raised and that is Dr Leigh’s report.  Your Honour referred to the ratio or the percentages that he gave of two to 20 per cent, which we can find in book three, page 912.  It is the last figure in his report where he says:

on an apportionment model, the fraction of causation attributable to asbestos is 2-20%.

He gave another number, I merely draw this to the Court’s attention, at page 904 at the last line where, applying some assumptions, he said that the figures in that paragraph, which I will not read out:

indicates an approximate apportionment of damages to asbestos of 2‑12% depending on model used.

There was some examination or cross‑examination about these matters.  That is contained in book 1, page 262 and following where he is asked about one model or one of his sets of figures producing – page 262, line 12.  He is talking about the two to 20 per cent and he explains it – but I will not read it out – but at page 263, line 3 he is talking about the two to 12 per cent.  There is more of that on page 264, at line 15 where Mr Watson says:

I just want to ask you, doctor:  with the modelling exercises which produced different figures of 2 per cent to 12 per cent, they were based upon that which you had said in your report, being a cumulative exposure in the two places of employment of eight fibre mil years?---Yes.

GORDON, MR:   Sorry, I think it’s 2 per cent to 20 per cent.

WATSON, MR:   No.

Doctor, you can clear it up for us.

HEENAN J:   2 to 12?---2 to 12 was one model, yes.

It appears that the majority accepted two to 12.  I refer the Court to appeal book 4, page 1510, paragraph 329 of their judgment.  The only figure I have been able to find in the majority’s judgment is what they say at paragraph 329:

Dr Leigh said that indicated an approximate apportionment to asbestos of between 2% ‑ 12% depending on the model used.

KIEFEL J:   Do I take it that you consider Dr Leigh is speaking of the same thing in those two different passages?

MR ABBOTT:   Yes.

KIEFEL J:   In the summary he is talking about the same thing?

MR ABBOTT:   Yes, but in our case of course at the end of the day whether it is two to 12 or two to 20, neither is enough.  Indeed, Dr Leigh was unable to say, as we have heard, what was the medical cause of lung cancer.  In his report and his evidence he speculates, in our submission, that it is cumulative in every case.  He plainly said in his report on two occasions that the state of medical evidence could not say that this was so.  Those two references are in appeal book 3 at page 900, approximately two‑thirds of the way down, where he said:

Even though Mr Cotton was a smoker, the asbestos exposure would have been a significant independent risk factor and would also have had a synergistic effect with tobacco in causing the lung cancer and thus made a material contribution to causation.

So he is not ruling out independence of the asbestos exposure.  At page 901 in the passage that has received attention, the last line two‑thirds of the way down, he starts off by saying:

While the precise mechanism of interaction between ‑ ‑ ‑

He concludes that by saying –

It is however true that exposure to either factor alone is capable of causing lung cancer.

One of the major errors which we identify in the submissions of my learned friend, both implicit in their written submissions and explicit in their oral submissions, is the assumption that tobacco and asbestos could not act independently when a person was exposed to both.  Of course, the corollary of that is that if it is cumulative in every case, why would you then ignore the background exposure from asbestos in determining whether a contribution was or was not material? 

May I pass then briefly to my second point.  My learned friend’s list of special facts.  When pressed he identified a number of special matters.  In our respectful submission, two of them are plainly not special.  The sequencing, in our submission, could not on any view be a special fact in this case.  The sequence is pretty much the same as his graph demonstrated and as the evidence demonstrates whether the cause be tobacco alone or asbestos alone or a combination of asbestos and tobacco together. 

The other special fact on which he relied was the young age.  In our respectful submission, that also is not a special fact.  It cannot be indicative of what he described as the so‑called extra damage from the combination of carcinogens because the death occurred within, as we learned, the bracket of normalcy.  I rely upon the passage from Chief Justice Martin in his judgment at book 4, page 1490, paragraph 257, of which I have already referred to in my submissions so I will not read it out again.  That contains a reference to a passage in the trial judge’s judgment which is to be found in appeal book 3 at page 1233, paragraph 400 of the trial judge’s judgment.

My third and last point in reply is that the claim by the respondent at paragraph 52 of their written submissions that, and as explained by my learned friend ‑ ‑ ‑

GUMMOW J:   What do you say about Mr Walker’s point 2?

MR ABBOTT:   I am sorry, your Honour?

GUMMOW J:   Mr Walker put to us three special links.  You dealt with two.  What about the other one, namely, elimination of true competing cause and, as an aspect of that, no alternative explanation?

MR ABBOTT:   We say there is an alternative explanation.  His explanation depends upon the cumulative operation at all times and we say that the medical evidence does not support, and indeed no evidence supports the cumulative operation at all times.  The claim by the respondent that the candidates for explanation of the cause of Mr Cotton’s lung cancer had been reduced to two by the time of trial is a claim which we say is not borne out, at least on our reading of the transcript.  My learned friend’s submission I think was to this effect that by the time the trial came, or at least by the time of judgment, or at least indeed by the time of appeal, there were only two candidates, tobacco and asbestos acting multiplicatively, and tobacco.

In our submission, on our reading, there were always four categories, on the evidence, tortious asbestos alone, tobacco alone, tobacco and tortious asbestos together or none of the above and the suggestion that although the medical evidence and the epidemiological evidence proceeded on three categories but in reality there were only two candidates in the field available for judicial consideration by the time the Full Court came to deal with the matter in our submission ignores the fact that there were four categories.

Of course, the consequence of the collapsing of the categories, as the respondent would have it, assumes that the carcinogens only act in accordance with the two categories in every case, that is, the collapsing of the categories is premised on the assumption or the proposition that the cause in every case could only have been tobacco or tobacco and asbestos, which, as I have said, is not on the whole of the evidence in our submission the evidence on which the Court could and should act.  Those are submissions.

FRENCH CJ:   Thank you, Mr Abbott.  Yes, Mr Jackson.

MR JACKSON:   Your Honours, may I say first of all, if your Honours were to go to the transcript of the argument yesterday afternoon at page 75, paragraph 3270, our learned friend, Mr Walker, he asked:

may I make it crystal clear it is always about causation in negligence actions.  It may or may not be exactly similar to causation in crime or causation in deliberate torts or causation in contract.  For the purposes of this argument, it is causation in negligence actions.

Well, of course, the judgment against us is a judgment in contract.  It is a judgment in contract for the reasons which appear in volume 3 at page 1370, paragraph 757, to put it shortly, your Honours, so that there would be no apportionment for contributory negligence.  You will see that at the bottom of page 1370, the top of page 1371, based on Astley. 

Now, your Honours, it is a case in contract and to prove more than nominal damages against us it is necessary to prove the damage occasioned by the breach of contract.  Now, your Honours, that reflects itself in two ways.  One is that it is necessary, in our submission, to isolate the effects of exposure to asbestos and, secondly, it is necessary to isolate the effects of exposure to asbestos while employed by us. 

Your Honours, even if one takes the view that the appropriate result on the evidence is that one can say that both were causes of the onset of the condition at the time when it occurred, to put the case at the highest, really, for the plaintiff in the matter, there is no reason in our submission why the right result would not have been – and your Honours, I use the past element of that tense for a reason, to which I will come in a moment – there is no reason why one would not have to attribute what proportion of the damage suffered by the plaintiff, or plaintiff’s family, was attributable to exposure to asbestos and in particular, exposure to asbestos during the term of our employment.

Your Honours, could I come back to dealing with why I say that was in the past tense.  I say immediately that the particular point was not taken at the trial, and that is why one does not see that issue discussed, but the issue does arise if one is trying to identify questions of causation and what is and how the issue operates in a particular case.  It does apply in relation to the second part, which I mentioned earlier and that is the question of the extent to which our negligence, our breach of contract relevantly is to be treated as responsible for the plaintiff’s damage.  Your Honours, I mention that also because the particular issue does not highlight the extent to which it is necessary to draw in the end a connection between exposure to asbestos and the damage - what is the connection?

Could I come then to the second aspect, and that is response to our learned friend’s submissions that this is a case of smoking plus asbestos, the two together, not two separate things.  Could I say a couple of things about that, your Honours.  The first is that there is no doubt, and your Honours, I know I am being repetitive in saying so, that either of the two matters, smoking or exposure to asbestos, can be a cause of lung cancer.  Your Honours, if one goes to the passage from Dr Leigh, the central passage relied on by the majority in the Court of Appeal at page 1512 of volume 4, one sees that it is the very thing that he said, either can be a cause. 

Your Honours, that has the consequence that one has to ask, was it caused in this case by smoking, was it caused by exposure to asbestos or was it cause by both?  In the passage to which I mentioned from Dr Leigh’s evidence, there is a recognition of the existence of those possibilities and it does become necessary in the particular case for immediate purposes to identify whether the evidence supported the contention that exposure to asbestos did play a part in the lung cancer.  If one went to look to see what was the evidence that might demonstrate that it did, Dr Leigh’s suggestion, of course, was that one went to the epidemiological modelling to arrive at the answer.  Your Honours, one then had to deal with the question whether that was material and, your Honours I will not take that further now.

Could I just say one further thing about it.  Our learned friend said this morning that all the medical evidence was to the effect that they combined and I think, your Honours, there may have been what would be in our favour something of a flourish to the effect that if the evidence was not to that effect then the respondent’s case failed.  Your Honours, I do not know that that necessarily follows but could we just say that if one goes to the evidence of Berry, it really does not seem to support the notion that inevitably there was a combination.

I wanted to go, your Honours, to three passages in his evidence.  One is a passage – it is in volume 1 – the passages commence at page 395.  It is really lines 1 to 20.  Your Honours have been taken to this passage already.  The particular part I wanted to refer to was the passage about line 15 to line 20 where he identified the fact that one could not say what was going on in a particular person’s body.  From there, your Honours, one goes to page 397 and you will see in the passage commencing line 21 to line 30 that he speaks about:

A clinical examination would say this person has got lung cancer and perhaps certain other things, but I don’t think it would assist in saying –

to put it shortly, what the cause was.  Then one comes to page 399.  At the bottom of page 399 in the last four lines:

an experienced clinician could express a view that because a certain person had been exposed to asbestos, and that exposure was before the disease, and because, based on epidemiological studies using the criteria which you have gone through, because from that we know that asbestos can cause lung cancer, then a clinician could say it might have caused lung cancer in this particular individual.

Either alone or in combination with cigarette smoking?‑‑‑Yes.

So, your Honours, one sees that there is an absolute clarity, absolute unanimity in saying, of course they operate in combination, except perhaps one can say there are de minimis cases.  The reality is that there remain possibilities.  Each could be a cause, could be caused in combination.

Could I come then, your Honours, to the question of inference and the couple of ways in which our learned friend’s case was put to the Court.  In reality, in our submission, the case on inference comes down to a summation of these things.  Exposure to asbestos is a possible cause of lung cancer.  The deceased was exposed to asbestos while working for us.  He died from lung cancer.  He was at the lower end of the range of people who may die from lung cancer. 

Now, your Honours, if there were no other possible cause, if he was a man who did not smoke, no other identified cause apart perhaps from the background group of people who, some quite famously, who die from something where there has been no smoke, or anything of that kind, but if there were no more, perhaps one might draw the inference that lung cancer was the cause of the – I am sorry – the exposure to asbestos was the cause of the lung cancer.

Your Honours, one does live in the real world and in the real world one sees that the predominant cause of lung cancer is smoking.  He was a smoker.  My learned friend cavilled a little at what I said at the commencement of our submissions yesterday.  The evidence at page 14 was to the effect that if you smoke and you smoke continuously and you live long enough and nothing else happens in between, you will end up dying of lung cancer.

So one sees that the predominant cause of lung cancer is smoking.  In the real world, in our submission, one would have to form the view that smoking caused the lung cancer.  But how then, if one is looking at the case as one of inference, is one to arrive at the view that the exposure to asbestos was also a cause?  Your Honours, it never remains, in our submission, more than a possibility and a possibility at a relevantly low level.

Your Honours, could I just say something more about the matter that was emphasised this morning, and that is the relatively young age of the deceased.  What our learned friend did was to refer to the evidence at page 21, volume 1, and in particular the passage between lines 16 and 20, where really all that was said was:

I thought this person is a young person who has developed cancer and I wonder what increased his risk so early in life.  If you have greater risks then it’s more likely you develop it earlier.

Your Honours, if one had a situation where, as was the case here, the age at which the deceased died was an age within the cohort, if I can use that word, or within the range of age of which people die from lung cancer, then all you have is that he is one at the lower end, the people at the higher end – you have to get a range from somewhere.  But to say that he is a young person but in the range, really does not, in our submission, advance the matter, and that is referred to by Chief Justice Martin at page 1490 in volume 4, paragraph 257.

Your Honour, may I conclude by saying something about the synergistic effect that was referred to and if I could just say this about it.  The synergistic effect is an observation drawn from the statistically higher incidence of cancers among persons who had been exposed to both agents.  Could I give your Honours a reference to where you will find that.  I will take your Honours to it.  It is Professor Musk in volume 1, page 8, lines 30 to 33, and Dr de Klerk, volume 1, page 374, lines 6 to 10.

There are various hypotheses as to why there is a synergistic effect.  By that I mean that there are various hypotheses about what biological processes explain the observation that there is a higher risk of cancer for persons exposed to both.  But the hypotheses, your Honours – and I will give reference to this in just a moment – are based around the fact that asbestos and tobacco act at different stages of cancer development and it is in that sense that they, in a sense, multiply rather than add to the risk.  You will see the reference to stages in Professor Musk at page 8 in volume 1 about lines 25 to 30 and perhaps a little earlier than that, but the answer commences about line 23.  Your Honours, I will not read it out, but you will see the reference to different stages in that answer.  That is the reference to the stages.

Then one sees a somewhat similar reference in the report of Dr Leigh at volume 3 page 900.  Your Honours will see a reference at the bottom of that page to the fact that there may be different stages involved and it goes over to the top of the next page and the reference to later stages in the third line at page 901.  Your Honours, the multistage model or the explanation or hypothesis for the synergistic effect does assume that the two agents act independently and, as a result of that, there is a form of multiplication of the independent probabilities to arrive at the probability that both will act.

The model, if I could go to Dr de Klerk’s evidence at page 373 in volume 1, and it is a passage, your Honours, that commences about line 20 on page 373 and it goes over to page 374, about line 13, but it has the effect that by the multiplication of the independent probabilities you arrive at the additional possibility that both agents will act and the result is that if one takes the figures that result from it, you do have, taking into account the independent activities at the different stages, you then have added to that a

figure that results from the multiplication of the two and in that way, if one looks at the results, the epidemiological evidence does take into account the synergistic effect and it takes into account by having it as an identified separate element.  Your Honours, those are our submissions.

FRENCH CJ:   Thank you, Mr Jackson.  The Court will reserve its decision.  We will adjourn until 10 o’clock tomorrow morning.

AT 3.01 PM THE MATTER WAS ADJOURNED