R v Pegios

[2008] NSWDC 105

CITATION:	R v Pegios [2008] NSWDC 105
HEARING DATE(S):	10,11,12,13, 16,17,18 June 2008
JUDGMENT DATE:	23 June 2008
JURISDICTION:	Criminal
JUDGMENT OF:	Murrell SC DCJ at 1
DECISION:	See paragraph 69
CATCHWORDS:	Manslaughter by gross negligence - dentist - death of patient - judge alone trial.
CASES CITED:	R v Misra [2004] EWCA Crim 2375, applying R v Adomako [1995] 1 AC 171. R v Bateman(1925) 19 Cr App R 8
PARTIES:	Department of Public Prosecution - Crown Dr G Pegios - Defendant
FILE NUMBER(S):	07/11/0232
COUNSEL:	Mr B Hughes - Crown Prosecutor Mr S Littlemore QC - Defendant
SOLICITORS:	The Office of the Director of Public Prosecution - Crown Guild Legal - Defendant

IN THE DISTRICT COURT
OF NEW SOUTH WALES

CORAM: JUDGE H.G. MURRELL SC

23 JUNE 2008

R v Pegios
No: 07/11/0232

JUDGMENT.

1 On 6 November 2002, the accused, a dentist, performed a dental implant procedure upon SC. The accused used intravenous sedation to allay SC's anxiety about the unpleasant 1.5-3 hour procedure. SC suffered a critical loss of blood oxygen saturation. On 8 November 2002, he died of hypoxic brain damage.

2 The accused was charged that, on 8 November 2002 at Kogarah, he unlawfully killed the deceased (manslaughter by gross negligence).

3 The Crown alleged that the accused was grossly negligent in that:

(1) while subjecting the deceased to sedation in his surgery, he negligently administered excessive drugs, causing the deceased to lose consciousness, and thereby risking airway compromise and oxygen desaturation; and
(2) he negligently failed to respond appropriately when the deceased experienced oxygen desaturation.

4 On 7 June 2008, the accused elected to be tried by a judge alone, and the DPP consented. I was satisfied that, before making the election, the accused had sought and received legal advice.

5 I now set out the principles of law that I apply and the findings of fact that I make for the purpose of arriving at a verdict.

General Directions

6 I am aware that the Crown has the task of proving the accused’s guilt beyond reasonable doubt. In other words, the Crown must prove beyond reasonable doubt each legal element of the charge and the essential facts necessary to establish each element.

7 I am aware that, in making findings of fact, I must rely upon the evidence. Matters of medical/dental expertise must be determined solely on the basis of the expert evidence adduced in the trial. In deciding the facts, I must apply my common sense.

8 The accused chose to give evidence on oath. It is not for the accused to prove his innocence but for the Crown to prove his guilt beyond reasonable doubt. However, as the accused chose to give evidence, I assess the reliability his evidence in the same way as I would assess that of any witness, taking account of factors such as inconsistency, inherent improbability and demeanor.

9 Although some of the experts were anaesthetists or specialist dentists, the accused's conduct must be assessed against that of a reasonable general dentist in the accused's position.

10 The experts expressed different - and, in some respects, conflicting - opinions about appropriate medication, about the course of medical events, and about if, when and how a reasonable general dentist would have responded to those events. Except in relation to the evidence of the accused (which may, in some respects, be characterised as expert evidence), there was no attack upon the honesty of any expert witness. In assessing the reliability of each expert's evidence, I must consider the accuracy and completeness of the facts and assumptions upon which the opinion was based. It is not a matter of choosing between the experts. Rather, if I decide that there is a reasonable possibility that an expert is correct about a critical matter and, if so, the Crown is unable to establish an element of the offence, then I must conclude that the Crown has failed to prove the element beyond reasonable doubt.

Elements of the Offence

11 In order to establish the offence, the Crown must prove beyond reasonable doubt that:

(1) the accused owed a duty of care to the deceased;
(2) by his act or omission, the accused negligently breached that duty of care;
(3) the accused's negligent act/omission caused the deceased's death; and
(4) considering the extent by which the accused's conduct fell short of a reasonable standard of care and the associated level of risk of death, the degree of the accused's negligence was so "gross" that it amounted to a crime.

12 There is no dispute that the dentist/ patient relationship gave rise to a duty of care (to take reasonable care to avoid foreseeable injury), or that the accused's acts/omissions caused the death of the deceased from hypoxic brain damage.

13 The contentious issues are:

(1) the substance of the relevant duty of care (what a fair and reasonable standard of care and competence required);
(2) whether I am satisfied beyond reasonable doubt that the accused negligently breached that duty by administering excessive sedative drugs and/ or by failing to take appropriate action when the deceased experienced oxygen desaturation (rather than simply misjudging the situation); and
(3) whether I am satisfied beyond reasonable doubt that the degree of any such negligence was so "gross" that the accused's conduct amounted to a crime against the State.

Dental Procedures Under Sedation

14 The spectrum of sedation ranges from conscious sedation (the patient is capable of continuous rational communication), through deeper sedation (the patient will respond to extreme stimulae) to unconscious sedation (general anaesthesia). Any sedation tends to depress respiratory function. If sedation goes beyond conscious sedation, it may result in oxygen desaturation (hypoxia) because the patient cannot voluntarily ensure that the airway is clear. If prolonged, hypoxia can damage the brain and heart. Restlessness is a "classic symptom" of hypoxia (Dr Vickers). Cyanosis, the development of a blue colour in the skin, commences when oxygen saturation drops to 80 - 85% (on average, at 83%). As discolouration first appears in the lips, it is easily seen by an operating dentist.

15 Because loss of consciousness may result in oxygen desaturation and the associated risk of serious injury or death, it is important that a health-care professional administering sedation maintain patient consciousness (if the procedure is being conducted under conscious sedation) and/or monitor oxygen saturation (to prevent a patient who is undergoing conscious sedation from falling into deep sedation/unconsciousness, or if the procedure is intentionally conducted while the patient is in deep sedation/ unconscious).

16 The "safe operating zone" is when a patient's oxygen saturation is over 95%. Generally, oxygen saturation should be maintained at a level above 90% (at least) and should be monitored by an oxymeter set to emit an alarm if saturation falls to 90% (or, perhaps, 92 - 93%). Below 90%, a patient is considered to be hypoxic, and the oxygen saturation level and the related partial pressure level (a measure of dissolved oxygen in the blood) may fall sharply. There is a high risk of damage if oxygen saturation falls below 75 - 80% (Dr Padley). A saturation level of 65% is a critical emergency that will "certainly have an adverse outcome" if it continues for 3 - 4 minutes (Dr Kaplan).

17 During dental procedures, bleeding from the mouth may result in airway obstruction, causing or contributing to oxygen desaturation. Suction is used to remove blood from the airway. An increase in blood pressure is associated with an increase in bleeding and the related risk of airway obstruction.

18 In 2002, the Australian and New Zealand College of Anaesthetists/Royal Australasian College of Dental Surgeons guideline on Sedation for Dental Procedures was P 21 (1996). It provided:

"Sedation for dental procedures includes the administration by any route or technique of all forms of drugs which result in depression of the central nervous system. The objective of these techniques is to produce a degree of sedation whereby rational communication with the patient is continuously possible , so that uncomfortable and/or stressful procedures may be facilitated. The drugs and techniques used should provide a margin of safety which is wide enough to render unintended loss of consciousness unlikely .
... it is important to understand ... that over sedation or airway obstruction may occur at any time ...
... if at any time such rational communication is lost, then the operator must cease the procedure and devote his/her entire attention to monitoring and treating the patient until such time as the patient recovers consciousness ... " (my emphasis)

19 In relation to oxygen loss, the P 21 guideline provided:

"3.7 If loss of consciousness, airway obstruction or cardiorespiratory insufficiency occur at any time, both the proceduralist and assistant must devote their entire attention to monitoring and treating the patient until recovery, or until such time as another medical practitioner becomes available to take responsibility for the patient 's care."

20 The University of Sydney conducted a diploma course in intravenous sedation for dentists wishing to perform intravenous sedation in the surgery. Exhibit 7 indicates that the University taught or is teaching that the sedative midazolam may be administered in a total dose of up to15 mg, and that "propofol is a very useful drug to help you through the last part of treatment", although propofol was not recommended if the total dose of midazolam had been administered "and the patient is still not sedated enough to start treatment" (my emphasis). The accused said that, when he undertook the diploma course, he was taught that, if "titrated to effect", 17 mg of midazolam may be appropriate for conscious sedation, and that it was "normal" to administer a combination of midazolam and propofol.

21 After the deceased's death, the accused researched propofol. He now believes that it is dangerous and should not be used in a dental surgery. Other witnesses gave evidence to the effect that, in recent years, propofol has fallen from favour as a sedative agent, although it is used in hospitals as an anaesthetic agent.

The Procedure on the Deceased

22 The deceased was 67 years old. He weighed 96 kg and was in apparently reasonable health for his age. He had a stocky build and a short, thick neck. He gave a history of alcohol abuse (alleged to have terminated recently) and very heavy cigarette use earlier in his life. He did not inform the accused about recent cardiac investigations, nor did he tell the accused that he was taking voltaren and a high daily dose of aspirin. Both drugs increase bleeding.

23 The accused performed a Novum implant procedure on the deceased. The procedure must be undertaken in one sitting. The accused had undertaken the implant manufacturer's training course and had completed 27 such procedures without incident. He had placed over 1,000 dental implants.

24 During the procedure, the accused was assisted by a very experienced registered nurse (who was responsible for checking the monitoring instruments) and two dental assistants.

25 The accused used local anaesthetic for pain management. He decided to administer intravenous sedation to allay the deceased's anxiety during the lengthy and unpleasant procedure. In 1999, he had completed the University of Sydney's diploma course. By November 2002, he had used intravenous sedation during more than 680 procedures.

26 Although he was not a member of either of the associations that had produced the guideline, the accused considered himself to be "bound" by P21 (1996). It had formed the basis of his training in sedation at the University of Sydney.

27 In order to sedate the deceased, the accused administered the drugs midazolam (total amount 17mg) and propofol (total amount 150 mg). He administered nitrous oxide through a nasal mask.

28 The accused employed an oxymeter to monitor blood oxygen saturation. It was set to emit an audible alarm if the deceased's oxygen saturation level fell below 90%. Digital oxymeter readings displayed continuously and were recorded by the registered nurse at five-minute intervals.

29 It was the accused's uncontested evidence that, during the procedure when the oxymeter sounded an alarm, he interrupted the procedure and extended the deceased's neck to open the airway (performed a "chin lift"). He did not recommence the procedure until the oxymeter showed that the deceased's oxygen saturation level had risen to 90%.

30 At about 9.20 or 9:30 am, the accused took a "bite registration" from the deceased. He could not have done so unless the deceased was conscious and cooperative.

31 The accused administered drugs and the nurse recorded the deceased's oxygen saturation levels as follows.

Time	Oxymeter reading	Midazolam	Propofol
8.00	86
8.02	84	1mg
8.10	94	1mg
Surgery commenced
8.14	1mg
8.15	96
8.18	1mg	20mg
8.20	95	1mg	10mg
8.23	1mg	10mg
8.25	96
8.27	1mg	10mg
8.30	95
8.31	1mg	10mg
8.33	1mg	10mg
8.35	84
8.36	1mg	20mg
8.39	1mg	20mg
8.40	89	1mg	10mg
8.41	1mg	10mg
8.45	91
8.48	1mg	10mg
8.50	88
8.52	1mg	10mg
8.55	94
9.00	73
9.05	88
9.10	90
9.15	85
9.20	88
9.25	91
9.30	86
9.35	94
9.40	90
9.45	63

32 At 9.45 - 9.50 am, the registered nurse told the accused that the deceased's blood pressure was falling. Surgery was terminated and emergency procedures were instituted. Unfortunately, before these procedures were fully implemented, the deceased sustained hypoxic brain damage from which he later died.

The Standard of Care

33 The standard of care required of the accused was that of the reasonable person in his position, ie a general dentist undertaking intravenous sedation in his/her surgery in 2002, who was exercising a fair and reasonable standard of care and competence to avoid foreseeable injury.

34 The expert evidence was all to the same effect as the P 21 guideline, ie that a reasonable general dentist would administer a level of sedation such as would enable the maintenance of rational communication throughout the procedure, allowing a margin of safety wide enough to render unintended loss of consciousness unlikely.

35 The accused considered himself "bound" by the guideline. He appreciated the importance of maintaining "rational communication" with the patient throughout the procedure. He acknowledged that "rational communication was essential" and said that, had the deceased become unconscious at any time, then "that was absolutely a breach of the guideline".

36 Although it was only a guideline, in relation to the administration of sedation I am satisfied beyond reasonable doubt that the P 21 guideline accurately expressed the substance of the standard of care expected of a reasonable general dentist in the accused's position in 2002. It would be a breach of that standard of care to administer drugs that were likely to cause a loss of consciousness.

37 All experts and the accused agreed that oxygen desaturation carries a risk of serious injury or death and, consequently, requires an immediate and appropriate response. The terms of paragraph 3.7 of the P 21 guideline - by which the accused considered himself "bound" - are to the same effect. I am satisfied beyond reasonable doubt that the standard of care expected of a reasonable general dentist in the accused's position in 2002 required that, when a patient exhibited oxygen desaturation, the dentist stop the procedure and "devote their entire attention to monitoring and treating the patient until recovery". Unfortunately, the guideline is silent on what constitutes "recovery".

The Expert Evidence on Sedation

38 Associate Professor Woods, a dental practitioner who authored "Guide to the Use of Drugs in Dentistry" (a text used in the University of Sydney course undertaken by the accused), said that the intravenous doses of midazolam and propofol "appear high but not excessive for a large person in good health" who failed to disclose a heart condition and medication regime that may have been relevant. With the benefit of a complete patient history, Associate Professor Woods would have preferred gaseous sedation with local anaesthesia, and would have undertaken shorter procedures. The procedure proved to have been "simply too long" for the deceased to tolerate.

39 Dr Viljoen, a dental surgeon with over 20 years experience in administering intravenous sedation, considered that the deceased was an appropriate patient for intravenous sedation in a dental surgery. He expressed surprise at the dose of 17 mg of midazolam, comparing it to the 5 mg dose usually required in the absence of the "potentiating effect" of propofol. He described the way in which the accused used midazolam and propofol as "very unusual" and referred to the "potentiating" or "synergistic" effect when those drugs were administered together (ie the combined effect of the drugs was not additive, but was multiplied, one drug exaggerated the side effects of the other). He opined that the use of both drugs was "potentially very likely to cause loss of consciousness, with all the dangers associated with the unconscious airway", and said that "loss of consciousness will almost certainly occur", contrary to the P 21 guideline.

40 Dr Jackson, a periodontist who has used intravenous sedation for about 20 years, said that "both the number and dosage of drugs administered in this case were excessive and unlikely to maintain a state of conscious sedation". He considered that 17 mg of midazolam was a high dose. He could not express a view about the propofol dose as he does not use that drug, but he noted the "potentiating effect" of the drug combination.

41 Dr Padley, an anaesthetist experienced in dental procedures, said that the deceased was an acceptable candidate for conscious sedation, but sedation should have been confined to conscious sedation. In accordance with the P 21 guideline, the drug regime should have provided a margin of safety wide enough to avoid loss of patient consciousness. He said that the doses of midazolam and propofol that were administered were "excessive and would be sufficient to render a 67-year-old man unconscious or semiconscious." He would have expected a dose of midazolam of up to 5 mg, but said that a lower dose should be employed when the drug is used in combination with an opanoid, such as the accused employed. The propofol should have been administered in small doses and with caution. The deceased was over-sedated and "was at risk of the complications of hypoxia, which are cardiac arrest and hypoxic brain injury". The combination of drugs was "very likely to have caused unconsciousness", although he could not say that unconsciousness certainly resulted, nor could he say when that occurred.

42 Dr Kaplan, an anaesthetist who has worked with dentists for 14 years, said that anything beyond conscious sedation was inappropriate in a dental surgery because of the risk of airway obstruction and associated complications. Disregarding the propofol dose, the quantity of midazolam used was excessive. Normally, a maximum of 5 mg of midazolam was required for a lengthy procedure. The maximum that he had used was 8 mg, and that was for a 4.5 hour procedure. Further, the drug combination was "synergistic". Propofol "potentiates" midazolam. The combined effect of the drugs "would certainly have made (the deceased) deeply sedated or possibly anaesthetised and there is some evidence that that is the case".

43 Dr Vickers, an oral and maxillofacial surgeon experienced in working with patients under intravenous sedation, gave evidence that, with the benefit of hindsight, the deceased was "totally unsuitable" to undertake a Novum procedure by a general dentist employing intravenous sedation. High-alcohol use patients can be difficult to sedate, and short, stocky patients such as the deceased have potential airway difficulties. Further, in his opinion, a dentist should not sedate a patient for as long as 1.5 - 3 hours (the period required for the Novum procedure) in a dental surgery. The overall undertaking was "far beyond the capacity of a general dentist". The deceased's death "was likely attributable to over-sedation and failure to maintain an airway", resulting in hypoxia. The deceased "was probably rendered unconscious by the sedation", although the time at which unconsciousness commenced was unclear. Dr Vickers described 17 mg of midazolam as "a high dose". He was scathing in his condemnation of the use of propofol, a general anaesthetic agent, for conscious sedation in the dental surgery. He said that even a small dose of propofol could lead to unconsciousness. He considered that it "was a fundamental error" for the University of Sydney Dental School sedation course to recommend the use of propofol in the dental surgery. Generally, Dr Vickers agreed with the views of Dr Padley, but he went further in relation to the use of propofol.

44 Dr Berne, a general dentist with long interest and great experience in implant surgery and intravenous sedation, said that the accused's conduct "would be widely accepted by our peers as competent", and "met the standard of reasonable care and skill required". Although he described the dose of midazolam as "above average for the normal patient" and said that "more drugs than usual were used during the procedure", Dr Berne disputed that the dose of midazolam was excessive. He strongly disagreed with the experts who expressed reservations about the use of propofol, describing its use as "almost mandatory in a dental surgery". Because of the very short half life of propofol, Dr Berne considered the drug to be harmless. Bravely contradicting the other experts (including Dr Vickers, who was called in the accused's case), he said that the deceased "was not adequately sedated during the procedure". He observed that heavy drinkers are often difficult to sedate or anaesthetise. Because the deceased had low oxygen saturation levels prior to the administration of any sedatives, Dr Berne disputed that sedation had depressed the deceased's oxygen saturation levels. When Dr Berne saw a picture of the deceased, it rang "an alarm bell" because of the danger of airway compromise associated with the deceased's short, thick neck. However, the prospect of having to perform many chin lifts to maintain the deceased's airway would not have deterred Dr Berne from undertaking the procedure.

Were Drugs Administered Negligently?

45 In order to establish negligence, more is required than medical error or misjudgment.

46 Disregarding the evidence of Associate Professor Woods and Dr Berne, the evidence was that, in isolation, the dose of midazolam greatly exceeded a dose appropriate to maintain conscious sedation. When the "synergistic" or "potentiating" effect of the drug combination was taken into account, the drug regime was likely to result in deep sedation, if not unconsciousness. In other words, the drug regime was likely to achieve an inappropriate loss of consciousness that was associated with a serious risk of injury.

47 The evidence of Dr Berne as to the harmless nature of propofol and the continuing "almost mandatory" need to use that drug in a dental surgery was fundamentally inconsistent with the evidence of all the other experts. It was contrary to the accused's current, well-informed view. I consider that Dr Berne's opinion on this subject is mistaken. I disregard it when determining whether the accused's drug regime was negligent.

48 However, the view of Associate Professor Woods that, given the deceased's known medical history, the doses of midazolam and propofol were "high but not excessive" cannot be ignored. Further, his view is reasonably consistent with the - albeit ambiguous - University of Sydney document that is Exhibit 7. Exhibit 7 does not clearly support but nor does it clearly contradict the accused's assertion that, during the University of Sydney course, he was taught that it was acceptable to give up to 17 mg of midazolam and "normal" to administer both midazolam and propofol.

49 The views of the other experts are very persuasive but, given the view of Associate Professor Woods, the contents of Exhibit 7 and the accused's uncontradicted evidence about the content of the University of Sydney diploma course, I am not satisfied beyond reasonable doubt that the accused's sedative drug regime breached the relevant standard of care in that, having regard to the deceased's known medical history, it should have been considered likely to cause a loss of consciousness.

The Expert Evidence on Terminating the Procedure

50 In Dr Viljoen's experience, it was rare for oxygen saturation to fall below 90%. He disapproved of the procedure continuing after 8.35 am as, from that time, the deceased must have been "mostly hypoxemic".

51 Dr Jackson said that "for a period of almost one hour, the dentist failed to take appropriate action to manage the situation when the pulse oxymeter was constantly alarming and the physical signs of hypoxia would have become increasingly apparent." In his opinion, "the physical signs of hypoxia (such as depression of respiration and cyanosis) would have been apparent long before (9.45am)." In Dr Jackson's opinion, the accused should have terminated the procedure after 8.40 am because "stopping the surgical procedure and extending the patient's neck to improve the airway was clearly and demonstrably failing to reverse the situation of a patient becoming increasingly hypoxic". Dr Jackson "absolutely would not have continued" past 9 am. Appropriate action would have included confirming that the patient was conscious and responsive, clearing the airway, administering oxygen using positive pressure ventilation, administering flumazinal to reverse the effect of midazolam, and contacting paramedics.

52 In Dr Padley's opinion, when the deceased's oxygen saturation level dropped to under 90%, the procedure should have been discontinued until the deceased was able to respond to rational communication. If necessary, antidote drugs should have been administered. Dr Padley would have stopped the procedure at 9 am, when the oxymeter gave a reading of 73%, as one should "always assume that the low pulse oxymetry reading is correct and only consider machine error when patient hypoxia has been definitely excluded." In his niew, the periodic interruption of the procedure was an inadequate response as the deceased must have been deeply sedated or unconscious.

53 Dr Kaplan said that, in the context of the preceding low readings, the reading of 73% at 9 am would have caused him to stop the procedure, provided that was possible.

54 In the context of the accused's lack of medical training, Dr Vickers expressed the opinion that "any error (the accused) made was one that an ordinary competent dentist could also have made".

55 Dr Berne said that, if he could not maintain a patient's oxygen saturation above 90%, then he would abandon the procedure.

Was the Accused's Response Negligent?

56 The accused stated that, when the deceased's oxygen saturation fell to 90% and the oxymeter alarm sounded, he interrupted the procedure. If the deceased's saturation level did not recover spontaneously, he performed a chin lift and waited until the oxygen level recovered. The deceased did not lose consciousness until 9.50 am. He formed that view because "the patient was moving his arms". There was "absolutely no doubt" that he maintained rational communication with the deceased up to that time.

57 The accused said that he remembered the occasion when the oxymeter reading fell to 73%. That reading was an artefact (false reading, often the product of patient movement causing the oxymeter sensor to become detached from the patient's finger). He firmly reattached the sensor and the oxygen saturation reading recovered spontaneously.

58 The accused said that "a lot of the readings were artefact". In cross examination, he went further, asserting that every reading under 90% was an artefact. Despite holding that view, he did respond to each low reading by interrupting the procedure until the reading recovered to over 90%. He agreed that, had the readings under 90% been accurate, he should have stopped the procedure. He did not terminate the procedure because he did not believe that the low readings were accurate.

59 Except for Associate Professor Woods (who did not comment on this issue, other than to say that the procedure was "too long") and Dr Berne (who considered that repeated chin lifts were an acceptable way to address a recurring problem of desaturation), the experts agreed that, because of the degree and duration of oxygen desaturation indicated by the oxymeter (and, according to some, by clinical signs which must have been present), the procedure should have been terminated by 9 am at the latest, and appropriate measures should have been taken to restore oxygen saturation. They disapproved of the lengthy delay between 9 am and 9.45 am, when the procedure was terminated and emergency action was taken.

60 In my view, it is necessary to decide whether the reading of 73% may have been an artefact, which was dismissed by the accused for good reason. If it was a genuine reading, then, arguably, it was so low that it called for immediate and drastic action.

61 Beneath the recorded reading of 73%, the registered nurse noted an upward arrow, consistent with the spontaneous recovery of oxygen saturation. The reading was very much lower than the surrounding recorded readings. A reading of 73% was well into the range where any cyanosis would have been obvious. According to the expert evidence, had the reading been genuine, one would have expected an associated change in blood pressure and pulse rate. There was no such change. Further, the accused impressed as a diligent person who wanted to maintain high standards. I accept that, had cyanosis been obvious, he probably would not have proceeded. In my view, the reading of 73% may have been an artefact which was dismissed by the accused for good reason.

62 On the other hand, there was no reason to dismiss all the other low readings on the basis that they were artefact. None of the experts - including Dr Berne - did so.

63 The accused said that, although he considered them to be false, he responded to the low readings, waiting for the oxymeter reading to rise and, apparently, accepting that the higher readings were accurate. In my view, the accused's evidence that he considered the low readings to be false probably reflects a mistaken recall of his thinking at the time. More likely, at the time, he accepted that most of the readings were accurate but pressed on because most were only a little below 90% and he was able to restore oxygen by repeated chin lifts. Further, he may have misinterpreted restlessness (the "classic symptom" of hypoxia) as rational communication. It does not really matter what the accused thought at the time because he is to be judged by an objective standard.

64 Disregarding the reading of 73%, it is the case that, between 8.35 am and 9.40 am, the accused continued to operate on the deceased although, according to the recorded oxygen saturation levels, the deceased was never in the "safe operating range" of at least 95% blood oxygen saturation. Of the 14 recorded readings, 10 readings were 90% or lower. The accused himself agreed that, if the readings under 90% were accurate, he should have stopped the procedure. I have no doubt that - with the exception of the 73% reading - most, if not all, of the low readings were accurate. Given the recurring low readings, lack of sustained recovery, and the serious risks associated with oxygen deprivation, a reasonable dentist in the accused's situation would have terminated the procedure well before 9.45 am. I am satisfied beyond reasonable doubt that, in this respect, the accused was negligent.

Degree of Negligence

65 The offence of manslaughter requires gross negligence in circumstances where what is at risk is the life of the individual to whom the accused owes a duty of care: R v Misra [2004] EWCA Crim 2375, applying R v Adomako [1995] 1 AC 171.

66 As to the degree of negligence needed to establish manslaughter, in R v Bateman (1925) 19 Cr App R 8 at 11, the Lord Chief Justice said:

"judges have used many epithets, such as "culpable," "criminal," "gross," "wicked," "clear," "complete." But, whatever epithet be used and whether an epithet be used or not, in order to establish criminal liability the facts must be such that, in the opinion of the jury, the negligence of the accused went beyond a mere matter of compensation between subjects and showed such disregard for the life and safety of others as to amount to a crime against the State and conduct deserving of punishment." (my emphasis)

67 On this issue, I found the view of Dr Vickers to be helpful. Dr Vickers said that "any errors of judgment (in sedation management) ... must be assessed in the light of (the accused 's) lack of medical training and knowledge that caused him to be unable to manage the many medical (as opposed to dental) crises that developed."

68 The accused had undertaken the standard University of Sydney diploma course for dentists wishing to use sedation in the dental surgery. He knew that repeated low oxygen saturation readings should cause a dentist to terminate a procedure, but, in the face of low readings, he negligently failed to terminate the procedure. However, that was probably because he did not fully appreciate the extent of the medical (as opposed to dental) crisis that was developing. One could not expect that a reasonable general dentist practising sedation would have been better informed that the accused. The deficiency was largely a deficiency in training and accreditation. The accused's negligent conduct fell well short of that which would "amount to a crime against the State and conduct deserving of punishment."

69 There will be a verdict of not guilty.