Reilly v Devcon Australia Pty Ltd - [2008] WASCA 84

JURISDICTION : SUPREME COURT OF WESTERN AUSTRALIA

TITLE OF COURT : THE COURT OF APPEAL (WA)

CITATION: REILLY -v- DEVCON AUSTRALIA PTY LTD [2008] WASCA 84

CORAM: STEYTLER P
MILLER JA
NEWNES AJA

HEARD: 6 FEBRUARY 2008

DELIVERED : 17 APRIL 2008

FILE NO/S: CACR 68 of 2007

BETWEEN: PETER JOHN PATRICK REILLY
Appellant
AND
DEVCON AUSTRALIA PTY LTD
Respondent

ON APPEAL FROM:
Jurisdiction              :  SUPREME COURT OF WESTERN AUSTRALIA
Coram  :MURRAY J
Citation  :REILLY -v- DEVCON AUSTRALIA PTY LTD [2007] WASC 106
File No  :SJA 1118 of 2005

Catchwords:

Occupational health and safety - Occupational Safety and Health Act 1984 (WA) - Control of workplace - Contractor - Circumstances in which a principal will be 'deemed employer' of a contractor - Relative expertise

Occupational health and safety - Definitions - Meaning of 'control' - Meaning of 'matters over which he has control' - Meaning of 'practicable'

Legislation:

Factories Act 1961 (UK), s 29(1)
Mines Safety and Inspection Act 1994 (WA), s 9(1)(a)
Occupational Safety and Health Act 1984 (WA), s 3(1), s 5, s 19, s 20, s 21, s 22, s 23
Occupational Health and Safety Act 1985 (Vic), s 21
Occupational Health, Safety and Welfare Act 1986 (SA), s 4(2), s 19(1)

Result:

Appeal dismissed

Category: A

Representation:

Counsel:

Appellant: Mr G W Tannin SC & Mr T C Russell
Respondent: Mr R W Richardson

Solicitors:

Appellant: State Solicitor for Western Australia
Respondent: DLA Phillips Fox

Case(s) referred to in judgment(s):

Chugg v Pacific Dunlop Ltd (1990) 170 CLR 249
Complete Scaffold Services Pty Ltd v Adelaide Brighton Cement Ltd [2001] SASC 199
Hamersley Iron Pty Ltd v Robertson (Unreported, WASC, Library No 980573, 2 October 1998)
Humberstone v Northern Timber Mills (1949) 79 CLR 389
Morrison v De Bono [2005] WASC 271; (2005) 147 IR 454
Nimmo v Alexander Cowan & Sons Ltd [1968] AC 107
R v ACR Roofing Pty Ltd [2004] VSCA 215; (2005) 11 VR 187
R v Associated Octel Ltd [1994] 4 All ER 1051
Reilly v Devcon Australia Pty Ltd [2007] WASC 106
Reilly v Tobiassen [2008] WASC 6
Stratton v Van Driel Ltd [1998] VSC 75; (1998) 87 IR 151

JUDGMENT OF THE COURT: This appeal concerns the construction of s 19(1) and s 19(4)(a) of the Occupational Safety and Health Act 1984 (WA) (Act).
On 18 September 2002 Mr Desmond Kelsh died as a result of the collapse of a building under construction in Myaree, south of Perth. The building under construction consisted of a series of showrooms in an area known as 'Melville Square'. Glenpoint Nominees Pty Ltd (Glenpoint) was the lessor of the land comprising the building site (Myaree site). The respondent (Devcon) was related to Glenpoint. The two companies had common directors and shareholders. Devcon was in charge of the development on the Myaree site. It engaged labour and ordered materials needed for the building process, although invoices in respect of these were paid by Glenpoint.
The showrooms were being built with pre‑cast concrete panels. A foundation concrete slab was poured. The panels, which were to form the walls of the building, were cast and positioned in stacks around the slab. Once ready to be erected, lifting equipment was attached to each panel so as to place it in a vertical position on the slab. Temporary braces were fixed to the newly erected panels. Once panels had been erected on opposite sides of the slab, structural steel rafters were added. Purlins were attached to the rafters. The roof would then be attached to the purlins.
Mr Kelsh was a rigger. He was the director of Kefo Steel Erection & Fabrication Pty Ltd (Kefo). Kefo had been engaged by Devcon pursuant to a written order dated 18 August 2002 to:
Provide all necessary labour on‑site for the supervision and erection of all structural steel and concrete tilted panels at Melville Square as per the agreed rates.
- Rigger supervisor = $45 per hour
- Rigger = $40 per hour.

Collapse of the building

On 18 September 2002 Mr Kelsh and another rigger, Mr Peter Hunt, were working on Unit 3 of the building under construction. By then, three of the walls of that unit had been erected. The fourth wall (the southern wall) was to have been constituted by the northern wall of Units 2 and 3. However, these units, which had previously been constructed, had been dismantled for reasons attributable to the building licence. Steel rafters had been attached to the eastern and western walls of Unit 3 by Kefo employees. Some bracing had been installed on the rafters along the western wall of the unit. A wire rope had been attached to one of the rafters near its apex. This was attached to the slab of the unit at two points and then tensioned, so as to stabilise the rafter to which it was attached. Purlins had been attached to the rafters. Mr Kelsh and Mr Hunt were sitting on another rafter, installing additional purlins. The rafter on which they were sitting, which had not yet been adequately secured, moved and then fell to the slab below. This caused other rafters and some panels to fall. Some of this material fell on top of Mr Kelsh, resulting in his death.

Prosecution of Glenpoint and Devcon

Arising out of this incident, Glenpoint and Devcon were prosecuted by the appellant. He is an officer of Worksafe Western Australia who had been authorised for that purpose by the Worksafe Western Australian Commission. The complaint, dated 15 September 2003, alleged (relevantly) that, being employers, the two companies had:
failed so far as was practicable to provide and maintain a working environment in which [their] employees were not exposed to hazards in contravention of section 19(1) of the … Act and by that contravention caused the death of an employee; contrary to section 19(7) of the Act.
Particulars of the complaint alleged, amongst other things, that it had been practicable for Glenpoint and Devcon 'to have ensured that … there was adequate lateral restraint of the steel roof beams during the erection of steel roof members of the building under construction' and that their failure to do so was the cause of the collapse (pars 4(a) and 10.7 of the particulars).

Section 19 of the Act

Section 19(1)(a) of the Act (since repealed) provides that:
An employer shall, so far as is practicable, provide and maintain a working environment in which his employees are not exposed to hazards and in particular, but without limiting the generality of the foregoing, an employer shall ‑
(a)provide and maintain workplaces, plant, and systems of work such that, so far as is practicable, his employees are not exposed to hazards;
The word 'employee' is defined in s 3(1) of the Act. It means, relevantly, 'a person by whom work is done under a contract of employment'. The word 'employer' was defined, so far as is relevant, as meaning 'a person by whom an employee is employed under a contract of employment'.
It was common cause that Mr Kelsh was not an employee of Glenpoint or Devcon within the meaning of the definition. However, the definition is extended by s 19(4) of the Act for the purposes of s 19. That subsection reads as follows:
(4)For the purposes of this section, where, in the course of a trade or business carried on by him, a person (in this section called 'the principal') engages another person (in this section called 'the contractor') to carry out work for the principal ‑
(a)the principal is deemed, in relation to matters over which he has control or, but for an agreement between him and the contractor to the contrary, would have had control, to be the employer of ‑
(i)the contractor; and
(ii)any person employed or engaged by the contractor to carry out or to assist in carrying out the work;
and
(b)the persons mentioned in paragraph (a)(i) and (ii) are deemed, in relation to those matters, to be employees of the principal.

The decision of the magistrate

The magistrate acquitted each of Glenpoint and Devcon. He found that it had not been proved that either had been an employer or deemed employer of Mr Kelsh.

The appeal to Murray J

The prosecutor appealed against Devcon's acquittal. There was no appeal against Glenpoint's acquittal.
The prosecutor asserted, in the appeal, that the magistrate should have found that it had been proved that Devcon was deemed, by s 19(4), to have been Mr Kelsh's employer 'in relation to a relevant matter over which Devcon had control'. The particulars to that single ground of appeal identified the 'relevant matter' as being 'the provision of adequate lateral restraint to the rafters in Unit 3'.
Murray J, who heard the appeal, dismissed it: Reilly v Devcon Australia Pty Ltd [2007] WASC 106. His reasoning was essentially as follows.
He said [28], first, that the question in relation to the application of s 19(4) was:
[W]hether that part of the system of work which involved the hazard of the collapse of the building under construction as a result of the lack of lateral restraint of the steel roof beams was a matter over which Devcon had control, in fact.
He then turned to the meaning of 'control' in s 19(4). There is no definition of that word in the Act. Accordingly, he sought assistance in ascertaining its meaning elsewhere. He considered the objects of the Act enumerated in s 5 and what had been said by Byrne J in Stratton v Van Driel Ltd [1998] VSC 75; (1998) 87 IR 151, 157, to each of which we will later return. Then, he arrived at the following conclusions [32] ‑ [35]:
In the first place, to have control is not at all the same thing as to exercise control. It is the capacity to control with which we are concerned. Secondly, the relevant question for s 19(4) will be whether the defendant is deemed to be the employer in relation to the hazard with which the prosecution is concerned. That will be the relevant matter over which the deemed employer must have control. Otherwise, in relation to the hazard to which the deemed employee was exposed in breach of the duty imposed by s 19(1), the defendant cannot be liable because it will not be an employer within the meaning of the extended definition provided by the Act.
The defendant will have control in relation to the relevant hazard, firstly, if he has by reason of the contractual relationship or otherwise, a legal right of control in the sense that he has a right to give directions which must be obeyed. There is no suggestion that that was the case here. Indeed, the contract in the form of the purchase order reserved the right of control in the form of 'supervision' to Kefo. That was part of what they were hired to do … To find that Kefo had a legal right to control the manner of performance of the work in relation to the hazard which would be created by the failure to provide adequate lateral restraint in the course of fixing the roofing steel rafters would not prevent the conclusion, if the evidence supported it, that the defendant also had control. In this context I agree that control may be joint or several.
Absent a legal capacity to control, the Court will be concerned with control in the sense of a capacity to exercise control by giving directions which would be obeyed. The fact of control will be found where a means of control could in fact be employed which would be effective in the sense that a direction given, for example, would be obeyed. Control within the meaning of the Act would not be found, in my opinion, if the proper conclusion from the evidence was that the person or entity whose activities were to be controlled, if given a direction concerned to eliminate or control a relevant hazard, would and could simply decline to follow it.
If control in this sense is to be found then, in my opinion, it will be a different question whether the control might or might not in fact have been exercised, and in respect of that question the relative expertise of the deemed employer and the deemed employee will be relevant. But that is a question concerned with whether or not there has been a contravention of s 19(1); whether or not there has been a breach of the duty imposed on the deemed employer; whether the deemed employer has done what was 'practicable', as that word is defined in s 3(1), in the circumstances of the case.
Murray J then turned to the facts. He said that, if 'control of the manner of fixing the roofing steel work so as to provide adequate lateral restraint to the rafters was to be found against the respondent, it rested in [Mr Svein] Tobiassen and [Mr Matthew] Fuller' [36]. Mr Tobiassen was a manager employed by Devcon and a registered builder. He was in charge of the building project. Mr Fuller was the site supervisor who reported to Mr Tobiassen. Murray J went on to make the following findings [37] ‑ [40]:
There was no evidence that either gave any relevant instruction, although there was evidence that Tobiassen was the person who arranged the contractors engaged by the respondent and organised when they came on site. There was evidence that Tobiassen gave instructions about the work to be performed in relation to fabrication of the wall panels. Fuller was also involved. He said he would direct contractors as to the timing of the work to be done, and there was evidence that both Tobiassen and Fuller knew what work Kefo's employees were performing on Unit 3 at the relevant time, in circumstances where, because of the dismantling of Units 1 and 2, additional arrangements in relation to the lateral restraint of rafters would need to be made, although Fuller certainly did not appreciate the significance of this.
The Magistrate made findings to the above effect. He found that the respondent, through Tobiassen and Fuller, had the ability and did in fact enforce safety standards on site, for example, in respect of the use of appropriate safety equipment. The appellant had, on 3 September 2002, conducted a site inspection at which a number of matters not related to Kefo's particular expertise and work were required to be rectified. He instructed Tobiassen about that. Tobiassen directed Fuller what needed to be done so that he might supervise the remedial work and Tobiassen was observed to give instructions to persons representing relevant contractors.
But I have been referred to no evidence and, having read the transcript, I have found none for myself, to suggest that Tobiassen and Fuller, or either of them, were at any time concerned to instruct an independent contractor about the manner of the performance of their work in respect of matters which fell within the particular expertise for which they had been engaged. Tobiassen did not give evidence and there was nothing in Fuller's evidence to suggest that either man, on behalf of the respondent, saw it as being within their province and authority to instruct contractors or their employees about the manner in which they should perform the expert work for which they were engaged, or that any such instruction by them would be accepted and followed by the subcontractors. The matters raised by the appellant at the previous site inspection which appear to have been the subject of instructions for their rectification included such things as shifting a brace which was located in a site access area, moving a portable toilet from a position where something might fall on it, and moving a panel which was leaning against another.
On the other hand, there was evidence from Hunt and other employees of Kefo that Mr Kelsh was the supervisor in charge of the rigging work involved in the erection of structural steel and concrete tilt panels. He gave the instructions as to how the work was to be performed. Their evidence, I think, tends to confirm that had they been given any instructions as to the manner of the performance of their work by Tobiassen and/or Fuller, their response would be to confirm with Kelsh that the direction was to be followed rather than that they would have accepted that they were obliged to do what they were told by Tobiassen or Fuller.
Murray J consequently concluded that the magistrate had not erred in the conclusion arrived at by him. However, he added that the magistrate had erroneously had regard to the relative expertise of Kefo and its employees, on the one hand, and Devcon and its employees, on the other, in considering whether or not Devcon had had control of the method of work adopted [41].
Murray J then turned to the question whether, if he was wrong in finding that Devcon had not been a deemed employer of Mr Kelsh, Devcon should be found to have contravened s 19(1) of the Act. He said that the answer to that question turned on what was 'practicable' in the provision and maintenance of the working environment in which Kefo and its employees had worked [44].
The word 'practicable' is defined in s 3(1) of the Act as follows:
'practicable' means reasonably practicable having regard, where the context permits, to ‑
(a)the severity of any potential injury or harm to health that may be involved, and the degree of risk of it occurring;
(b)the state of knowledge about ‑
(i)the injury or harm to health referred to in paragraph (a);
(ii)the risk of that injury or harm to health occurring; and
(iii)means of removing or mitigating the risk or mitigating the potential injury or harm to health;
and
(c)the availability, suitability, and cost of the means referred to in paragraph (b) (iii).
Murray J said, in this respect [47]:
[T]he question in relation to the issue of contravention of s 19(1) would have been whether it was reasonable for those representing Devcon, Tobiassen, the registered builder, and Fuller, the site supervisor, to have inquired into the sufficiency of the system of work employed by Kefo, necessarily taking expert advice as the work progressed to ensure that adequate lateral restraint was provided. It was not that it was impracticable to take measures to eliminate the hazard. The question was whether it was reasonable to require that of the respondent when the measures to be taken all involved the application of expertise which those acting for Devcon lacked, but which was squarely within the special skill and expertise of Kefo and its workers.
He went on [48] to refer to what had been said by Steytler J in Hamersley Iron Pty Ltd v Robertson (Unreported, WASC, Library No 980573, 2 October 1998) 20, in the context of s 9(1)(a) of the Mines Safety and Inspection Act 1994 (WA), as follows:
Here, the personal duty imposed upon the employer is, as I have said, that of providing a safe workplace, so far as is practicable. If that, in turn, requires the employer to call upon expertise which it does not itself have then there is no reason why it should not do so and, indeed, every reason why it should. Moreover, in considering whether it did what it could, so far as was practicable, to ensure that those upon whom it relied in turn exercised reasonable care its own lack of expertise (if any) and the expertise of the independent contractor must be taken into account. If the task undertaken by the independent contractor is one which demonstrably falls within its area of expertise and outside that of the employer and if the task reasonably appears to the employer, who has such knowledge of the matters specified in s 9(1)(b) of the Act as might be expected to be had by employers of its kind, to have been carefully and safely performed by the independent contractor then it would ordinarily be difficult to conclude that the employer had breached the duty put upon it by the Act. It would not, in circumstances of that kind, ordinarily have been practicable for it to have done more.
Murray J said, in that respect ([49] and [50]):
In my opinion, those observations would be apt in this case given that the remedial measures to eliminate the particular hazard which led to the accident which caused Mr Kelsh's death were matters squarely within the expertise of Kefo and given that (as the Magistrate found) Kefo represented to Devcon that it had the necessary expertise, as it appeared that it did. It was not unreasonable for Devcon to rely upon Kefo to apply that expertise so as to discharge the duty imposed on Devcon to do what was reasonably practicable to provide and maintain a safe working environment.
To put the matter in terms of an alleged contravention of s 19(1) [it] would not, in my opinion, in this case be open to find that contravention on the basis that to discharge the duty to do what was reasonably practicable, Devcon was required to do more than to rely upon the known expertise of Kefo. Had I been required by a conclusion that the Magistrate fell into error in this case, to deal with the question of breach of duty, I would not have allowed the appeal because, in my view, the circumstances of this case could not sustain the conclusion that the respondent contravened s 19(1).

Grounds of appeal to this court

There are three grounds of appeal against the decision of Murray J. Omitting particulars, these read as follows:
1.The learned Judge erred in fact and law in failing to find that the learned Magistrate had erred in finding that the matter which constituted the 'hazard' was not something 'over which [the Respondent] had control' within the meaning of s 19(4)(a) of the Occupational Safety and Health Act 1984 ('OSHA').
2.The learned Judge erred in fact and law in characterising the Respondent's alleged breach of OSHA s 19(1) as having been related to the 'system of work' which was adopted by the Kefo employees.
3.The learned Judge erred in fact and law in determining that it had not been established by evidence adduced at trial that it would have been 'practicable' for the Respondent to have removed the 'hazard' (assuming that there had been a finding of 'capacity to control').

Ground 1 - Control

The particulars to ground 1 read as follows:
1.1The learned Judge correctly held that:
(a)the question was whether the Respondent had the 'capacity to exercise control', and not whether it had 'exercised control';
(b)there could be a 'capacity to exercise control' in the absence of any identifiable 'legal right to exercise control';
(c)such a 'capacity to exercise control' would exist where the Respondent could have given directions and/or taken other action which would have resulted in the avoidance of the 'hazard'; and
(d)any 'disparity' in expertise which had been found to exist between the Respondent and the employees of Kefo Steel Erection and Fabrication Pty Ltd (Kefo) was an irrelevant consideration in determining whether that 'capacity' existed.
1.2It followed that the learned Judge upheld Particulars (i), (ii), and (iv) of the Appellant's Ground of Appeal.
1.3The only remaining issue for the learned Judge, raised by Particular (iii) of the Appellant's Ground of Appeal, was whether the evidence established beyond reasonable doubt that there was 'capacity to control'.
1.4The learned Judge could not take into account any 'expertise disparity' in determining that question, and was therefore left only with the 'inferential evidence' which the Appellant had relied upon at trial.
1.5That evidence clearly established that the Respondent had given directions which were obeyed by Kefo employees in relation to matters which were an intrinsic part of the process of construction using the tilt‑up method.
1.6The learned Magistrate provided no reasons to support the distinction drawn between that demonstrated 'capacity to control' and the 'capacity' in issue, once 'expertise disparity' is excluded. Therefore, the learned Judge could not uphold that finding of fact without providing adequate reasons which would support such a distinction.
The appellant accepts, in relation to ground 1, that Murray J correctly identified the relevant 'matter', for the purposes of s 19(4), as the provision of adequate 'lateral restraint of the steel roof beams' of the building under construction. He also accepts that Murray J correctly found that, if Devcon had the capacity to exercise control over the relevant matter, this control rested with Mr Tobiassen and Mr Fuller.

Relevant evidence and the contentions advanced in respect of it

The evidence relied upon by the appellant in asserting that Mr Tobiassen and Mr Fuller had control over the provision of 'adequate lateral restraint of the steel roof beams' is essentially as follows. Mr Tobiassen was, as we have said, a registered builder. As Murray J pointed out, he did not give evidence at the trial. However, Mr Michael Hodgson, a director of Devcon, said that Mr Tobiassen was 'in control' of the development of the Myaree site. He also said that Mr Tobiassen was responsible for ensuring the 'quality of the construction work' and that Mr Tobiassen and Mr Fuller were responsible for ensuring that the work was carried out in accordance with the Act and regulations made under the Act (regulations). Mr Hodgson said that Mr Fuller, in his capacity as supervisor of construction work at the Myaree site, reported to Mr Tobiassen. Both were physically present at the Myaree site and, hence, in a position to exercise 'control' over it. All decisions concerning who was to be allowed to work on site were made by Mr Tobiassen. He told Mr Fuller which subcontractors would be turning up and when. We have mentioned that Units 1 and 2 had been erected before work commenced on Unit 3. Mr Tobiassen made a decision, given effect by Kefo, to dismantle these units and then to commence the erection of Unit 3. We have said that that direction was given because of licensing considerations. It had nothing to with the quality of the construction work. Other instructions were given by each of Mr Tobiassen and Mr Fuller to various contractors on the site. These were obeyed.
However, there was no evidence of any instruction given by either Mr Tobiassen or Mr Fuller (who gave evidence at the trial) in relation to the manner of erection of tilt panels or steelworks. We have mentioned that the trial judge made the (unchallenged) finding that Mr Kelsh was the supervisor in charge of the rigging work involved in the erection of structural steel and concrete tilt panels. He gave instructions as to how the work was to be performed. We have also mentioned the (unchallenged) findings that:
(a)there was no evidence to suggest that either of Mr Tobiassen or Mr Fuller was at any time concerned to instruct an independent contractor about the manner of the performance of work in respect of matters which fell within the particular expertise for which the contractor had been engaged; and
(b)if employees of Kefo had been given any instructions by Mr Tobiassen or Mr Fuller as to the manner of the performance of their work, they would have confirmed with Mr Kelsh that the direction was to be followed and would not have accepted that they were obliged to do as they were told by Mr Tobiassen or Mr Fuller.
As will be apparent, s 19(4) of the Act provides for the circumstances in which a principal is deemed, for the purposes of s 19, to be the employer of employees of a contractor engaged by the principal, in the course of a trade or business carried on by it, to carry out work for the principal. The subsection provides that the deeming provision will operate 'in relation to matters over which [the principal] has control or, but for an agreement between him and the contractor to the contrary, would have had control'.
Both parties accepted, before Murray J (and presumably before the magistrate), that there was nothing in the contractual relationship between Devcon and Kefo that gave Devcon a contractual right to control the manner in which Kefo performed the work undertaken by it (or that excluded control by Devcon in relation to any relevant matter). There is no challenge to Murray J's finding that Devcon had no legal right of control over the relevant 'matter', in the sense of a right to give directions, which must be obeyed, concerning that 'matter'. As will be apparent, no argument to the contrary had been put to him.
Consequently, the sole basis for the assertion that Devcon had control over the 'relevant matter' identified by the appellant (the provision of adequate lateral restraint over each steel roof beam) is that Mr Tobiassen, as the registered builder, and Mr Fuller, as the supervisor of construction work at the Myaree site, had overall control of the site and of what took place there. Although it is not contended that this control extended to a right to give directions concerning the manner of the provision, by Kefo, of adequate lateral restraints over each roof beam, counsel for the appellant suggested that the two men, or either of them, could have stopped work on the site until adequate restraints had been provided.

The meaning of 'matters over which he has control' in s 19(4)

That brings us back to the statute, and to the meaning of the words 'matters over which [the principal] has control'. Those words must be considered in their context, having regard for the purpose of s 19 and the objects of the Act.
We have said that the objects of the Act are listed in s 5. Those that are presently relevant read as follows:
(a)to promote and secure the safety and health of persons at work;
(b)to protect persons at work against hazards;
(c)to assist in securing safe and hygienic work environments;
(d)to reduce, eliminate and control the hazards to which persons are exposed at work …
A 'hazard' is defined in s 3(1) to mean (relevantly) anything that may result in injury or harm to the health of a person.
Section 19 is directed at ensuring, so far as is practicable, that employees will have a safe working environment. Subsection (4) promotes that objective by providing that responsibility for the safety of workers at a workplace is not to be the exclusive concern of the employer of the workers concerned. The principal who has engaged an employer to perform work at a workplace is to share that responsibility where it has control over a matter or matters affecting workplace safety.
Section 19 is one of a number of provisions in Part III of the Act that are designed to ensure workplace safety and health. Section 20 places duties on employees to ensure their own safety and health at work and to avoid adversely affecting the safety or health of others. Section 21 requires an employer, or a self‑employed person, to take reasonable care to ensure his own safety and health at work and, so far as is practicable, to ensure that the safety or health of a person, not being his employee, is not adversely affected by the work in which he or any of his employees is engaged. Section 22(1) provides that:
A person who has, to any extent, control of ‑
(a)a workplace where persons who are not employees of that person work or are likely to be in the course of their work; or
(b)the means of access to and egress from a workplace,
shall take such measures as are practicable to ensure that the workplace, or the means of access to or egress from the workplace, as the case may be, are such that persons who are at the workplace or use the means of access to and egress from the workplace are not exposed to hazards.
Section 23 places obligations concerning safety on designers, manufacturers, importers or suppliers of plant for use at a workplace.
Looked at in its overall context, s 19 is designed to ensure that those who are most directly responsible for the safety of workers (their employers and principals who have contracted with their employers and who have actual control over matters affecting their safety) should be held liable for default in exercising that responsibility. That the control must be actual control (encompassing a right of actual control, whether exercised or not) over the particular matter affecting safety seems to us to be evident from the words used, read in their context.
It is significant that s 19(4) is directed to 'matters' over which the principal has control, unlike s 22(1) which is directed to a person who has, to any extent, control of 'a workplace' or of the means of access to and egress from it. This suggests that s 19(4) is concerned with actual control over a particular matter affecting safety, rather than general responsibility for, or control over, the workplace. That reinforces the notion that the legislature did not intend to impose upon a principal who has engaged a specialist contractor (who is not ordinarily susceptible to direction as to how to perform its work: see, for example, Humberstone v Northern Timber Mills (1949) 79 CLR 389, 404 (Dixon J)) a general obligation to supervise the manner in which the contractor (having an expertise that the principal lacks) goes about the performance of the work entrusted to it.
A construction that imposed such a far‑reaching obligation on a principal would produce unworkable consequences. There is no real scope for a principal (lacking the requisite expertise) to exercise actual control over the detailed manner of performance of work by a specialist subcontractor. If it endeavoured to do so, this would be more likely to lead to hazards than to avoid them. Counsel for the appellant suggested, in this respect, that the principal might be required, in such a case, to engage an expert to oversee the method of work adopted by the expert subcontractor. That solution seems to us to be unworkable. A builder (for example) would have to 'double up', at significant cost, on contractors having specialist expertise. Work performed by a plumber or electrician would have to be overseen by another plumber or electrician (whose manner of supervision of the work of the first plumber or electrician would, on this construction, also be subject to the control of the builder).
Moreover, the construction that we prefer is consistent with that given to similar legislation in other States.
It is not in conflict with that given by Byrne J to s 21 of the OccupationalHealth and Safety Act 1985 (Vic) in Stratton. That section imposed duties upon employers to take steps to protect employees from injury. Section 21(3) reads as follows:
(3)For the purposes of sub‑sections (1) and (2) ‑
(a)'employee' includes an independent contractor engaged by an employer and any employees of the independent contractor; and
(b)the duties of an employer under those sub‑sections extend to such an independent contractor, and the independent contractor's employees, in relation to matters over which the employer ‑
(i)has control; or
(ii)would have control but for any agreement between the employer and the independent contractor to the contrary.
Byrne J said that [19]:
Given the great variety of circumstances in which s 21(3) may apply, it is neither desirable nor profitable for me to attempt anything like an exhaustive analysis of the word 'control' or the expression 'have control over' and I do not do so. In the present case, that which is the subject matter of the alleged duty is the manner in which [the worker] went about his work on the roof without protection from the risk of injury should he fall. The question for determination is in what circumstances, if at all, it might be said that this activity was under the control of [the employer of the independent contractor] where no direction was given by [it] as to this activity. In such a case, [the employer of the independent contractor] would, in ordinary speech, be said to have control over the activity in at least two situations. The first is where it had a legal right to direct that [the worker] not perform the work in that way. The second is where, notwithstanding that the person has no right to give it, the employer saw it as within its area of authority to give such a direction and, importantly, the worker would accept it and act upon it. It matters not in either situation that other persons might also have control over the same activity.
Our preferred construction of s 19(4) is consistent with that given to s 4(2) of the Occupational Health, Safety and Welfare Act 1986 (SA) (OHSW Act) in Complete Scaffold Services Pty Ltd v Adelaide Brighton Cement Ltd [2001] SASC 199. Section 19(1) of that Act requires an employer, in respect of each employee employed or engaged by it, to ensure, so far as is reasonably practicable, that, while at work, the employee is safe from injury and risks to health. Section 4(2) provides that:
For the purposes of this Act, where a person ('the contractor') is engaged to perform work for another person ('the principal') in the course of a trade or business carried on by the principal, the contractor, and any person employed or engaged by the contractor to carry out or to assist in carrying out the work, shall be deemed to be employed by the principal but the principal's duties under this Act in relation to them extend only to matters over which the principal has control or would have control but for some agreement to the contrary between the principal and the contractor.
The case concerned an accident that had taken place when a worker employed by a company, Allied Engineering Pty Ltd (Allied), fell from unstable scaffolding that had been erected by the appellant (Scaffolding). Allied had entered into a contract with the respondent (ABC) to carry out maintenance work for ABC at its premises. ABC had contracted with Scaffolding to provide and erect the necessary scaffolding.
Doyle CJ (Williams & Martin JJ concurring) said ([56] and [57]):
'Control' in s 4(2) of the OHSW Act should be read as referring to actual control, that is to things which the deemed employer is managing or organising. Unless s 4(2) is limited in this way, its reach would be very great. Control over this task rested with Scaffolding, as the expert contractor hired to perform the work. Nor was the placement of scaffolding something over which ABC would have had control 'but for some agreement to the contrary between [ABC] and [Allied]'. To the extent that ABC surrendered control over the erection of scaffolding, it did so pursuant to an agreement between ABC and Scaffolding. The same conclusion can be reached through the provisions of s 19(1) itself. On the evidence, ABC did 'ensure so far as is reasonably practicable' that [the worker] was safe. The arrangements that it made, and the precautions that it took before work began, were all that it was reasonably practicable for ABC to do, short of itself supervising Allied and Scaffolding in all the details of the performance of their work. I cannot think of any precaution that ABC should have taken, which one would regard as something that was reasonably practical, that is likely to have prevented the accident occurring. I accept that the duty imposed by s 19(1) is a higher duty than is imposed at common law, but it is not an absolute duty.
In what I have said so far I proceed on the basis that as a deemed employer ABC is not to be treated as responsible, as of course, for a failure by Scaffolding. One must consider … what it was reasonably practicable for ABC to do as a deemed employer of [the worker] who was on site as a worker employed by a contractor, the contractor being hired to carry out specialised work for ABC. In short, in my opinion, it was not reasonably practicable for ABC to exercise supervision at the level that would have been required to prevent this accident occurring.
Counsel for the appellant placed considerable reliance upon the judgment of EM Heenan J in Reilly v Tobiassen [2008] WASC 6. That case involved a successful appeal against the acquittal of Mr Tobiassen, by a different magistrate, on charges arising out of his overall supervision of the Myaree site. None of the charges brought against Mr Tobiassen alleged a breach of s 19 of the Act. Each of the charges against him alleged breaches of one or other of s 21, s 22 and s 23 of the Act or of the regulations.
Of the allegations that were made against Mr Tobiassen, the most relevant for present purposes is one that practical measures could have been taken by him in relation to a foreseeable hazard (the risk of the collapse of the steel roof rafters and the concrete tilt panels) by ensuring that there was adequate lateral restraint of the steel roof beams in Unit 3 during, and following, the erection of the rafters. In the course of dealing with this allegation, made in respect of a charge brought under s 22(1) of the Act (quoted earlier in these reasons), EM Heenan J found it necessary to consider the concept of 'control' for the purposes of that section. He said [91] ‑ [92]:
The analysis adopted by the learned magistrate proceeds on the footing that there can only be one person in 'control' of the workplace in the relevant sense, and for that control to exist it must contain an element of knowledge, skill and experience and the ability to recognise the need for corrective action and the power to enforce it. No doubt, if all those features existed, it could be rightly said of a person who possessed those attributes, that he or she was in control of the particular situation. However, to conclude this does not exclude the possibility that someone else may also have control, even if it be of broader scope or at a higher level of responsibility. For example, a power to order a subcontractor to cease work or to leave the site or to suspend operations, possessed by a supervisor or, for that matter, by the builder, would be to have control of the workplace because, through the exercise of that power, the conduct - at least the non-conforming conduct - of the contractor or its workers can be controlled.
The word 'control' is not specifically defined by the Act but in s 22(3), as it then was, it is provided that:
'A reference in this section to a person having control of any workplace or means of access to or egress from a workplace is a reference to a person having control of that workplace or that means of access or egress in connection with the carrying on by that person of a trade, business or undertaking (whether for profit or not)'.

Then, after having made some additional comments, EM Heenan J went on to say, first, that all persons who share in the control of building operations or work at a worksite have the obligation to exercise that control by taking practical measures to ensure that the workplace does not expose other persons on site to hazards [95]. He went on to say that the degree of obligation and the nature and extent of the duty will vary according to whether the influence of the particular person who bears the designated duty is greater or less; and that there was 'no reason to approach this legislation on the assumption that there are no concurrent or overlapping duties by the persons or categories of persons upon whom the statute has placed obligations' [97]. He also said [98]:
In my view, within the context of s 22(1)(a), 'control' means the ability of any person to whom the section applies (that is, who is constructing the building and who is not an employee) to use the influence associated with that control to install, maintain and enforce appropriate safe working practices and to avoid ascertainable hazards so far as is practicable.
He reached the following conclusion concerning Mr Tobiassen's liability under s 22 [99]:
The terms of the respondent's employment, his powers and duties under the Builders' Registration Act and his associated ability to give directions, means that this respondent did have control over this workplace to ensure that all others working at the site, including sub-contractors, complied with the terms of their contracts and the statutory and other duties to ensure that safe working measure and precautions were taken in the performance of their work. The respondent had the power to require the riggers to perform work to acceptable standards and could, if he had wished, order a halt or suspension of their operations until they did so. He never attempted to do this. However, it cannot be doubted that he had the power to do so, and that amounts to the influence or 'control' of which the section speaks.
Finally, for present purposes, in the course of making a number of factual observations concerning the evidence that had been before the magistrate in that case, EM Heenan J mentioned [100] that s 22(1) of the Act imposed a duty upon any person who has 'to any extent' control of a workplace. He referred to Morrison v De Bono [2005] WASC 271; (2005) 147 IR 454 [12] (Le Miere J) in support of the proposition that 'control', for the purposes of that section, consequently encompassed 'various degrees of control'.
For the purposes of this appeal it is unnecessary to express any opinion concerning the proper construction of s 22, or in respect of the conclusions arrived at by EM Heenan J with regard to the extent of the control over the workplace that Mr Tobiassen had for the purposes of that section. It is enough to say that, in our opinion, the reasoning of EM Heenan J is not apposite to s 19, for the reasons we have given. As we have said, s 19(4) is directed to 'matters' over which the principal has control and is concerned with actual control over a particular matter affecting safety, rather than general responsibility for, or control over, the workplace. We have also said that the legislature should not be taken to have intended to impose upon a principal who engages a specialist contractor some general obligation to supervise the manner in which the contractor (having expertise that the principal lacks) goes about the performance of its work. We have mentioned that this construction accords with that given to similar legislation in other states, particularly the South Australian legislation considered in Complete Scaffold Services.
We have also said that in the present case it is (and was) not contended that Devcon had any 'legal right' to direct Kefo as to the appropriate means of providing 'adequate lateral restraint' to the rafters, being, as we have stressed, the relevant 'matter' identified by the appellant. Nor is it suggested that the evidence at the trial established that the lack of adequate lateral restraint to the rafters was apparent, or should have been apparent, to Devcon, notwithstanding its lack of relevant expertise (we should add that the evidence at the trial was that rigging work can only be done by a person certified by Worksafe as qualified for that purpose). The only evidence in that respect was given by persons with rigging expertise (one of whom was the appellant). They said no more than that, relying upon their specialist knowledge of rigging practices, they considered that the method of work adopted by Kefo had been unsafe because the steel rafters had lacked adequate lateral restraint at the time of the collapse.
Finally, we have stressed that there is no challenge to the primary judge's finding [40] that Kefo's employees took instructions as to how their work was to be performed from Mr Kelsh and that, had either Mr Tobiassen or Mr Fuller instructed them in that respect, they would not have regarded themselves as obliged to follow that instruction unless directed by Mr Kelsh to do so.
It follows that Devcon was not proved to have been in control, for the purposes of s 19(4), of the only relevant 'matter' identified by the appellant and was rightly acquitted of the charge brought against it. Ground 1 consequently fails.
Although it is unnecessary for us to consider grounds 2 and 3, we will do so.

Ground 2 - System of work

The particulars to ground 2 (which asserts that the primary judge erred in characterising the alleged breach of s 19(1) as having been related to the 'system of work' adopted by Kefo's employees) read as follows:
2.1The Respondent was charged with having failed to provide a safe working environment; there had been no election to proceed on the more narrow basis of a s 19(1)(a) failure to provide a safe system of work.
2.2The Kefo employees were not exposed to the 'hazard' by the 'system of work' they were adopting, but by the state of the premises (in Unit 3). Unit 3 was dangerous to anyone in the vicinity, not merely to the deceased and Mr Hunt.
2.3The 'working environment' was a 'hazard' on the day of the accident, not because of any improper 'system of work' then being adopted by the Kefo employees, but because the rafters lacked adequate lateral restraint.
2.4The 'working environment' had been in that 'hazard[ous]' state since the erection of the steelwork the previous day. The question was whether the Respondent failed to ensure that it was not in that state on the day of the accident.
2.5There was no 'safe system of work' which could have been adopted once the 'hazard' had come into existence.
2.6The Respondent needed to identify the 'hazard' and stop any work in Unit 3 until it had been removed.
2.7It was not the prosecution case that the Respondent's failure consisted only in not preventing the 'hazard' from coming into existence. The failure extended from its creation to its manifestation in the accident.
It is important to read these particulars in the context of the case that was made against the appellant at the trial. As we have stressed, the breach relied upon was Devcon's alleged failure to ensure, relevantly, that there was adequate lateral restraint of the steel roof beams during the erection, by Kefo, of steel roof members of the building under construction. What was done by Kefo in that respect formed part of the process ordinarily adopted by it when erecting buildings of this kind and in that sense related to the 'system of work' adopted by its employees, as found by Murray J. As we understand the reasons of the primary judge, it was only in this sense that he said [43] that the prosecution was concerned with 'the system of work employed by Kefo and its workers in fixing the structural steel such that the rafters were … deprived of adequate lateral restraint'.
Murray J did not overlook the appellant's contention that the system of work adopted by Kefo in fixing the structural steel rafters had the result that Unit 3 was, at the material time, in a state that constituted a hazard to people working in the vicinity. Nor did he overlook the contention that Devcon had an obligation to identify the hazard and stop work at the site until the hazard had been removed. He consequently made no material error in these respects. To the extent that the particulars to ground 2 raise additional matters of substance, these have already been addressed when dealing with ground 1.
Ground 2 consequently fails.

Ground 3 - Practicable

As will be apparent, ground 3 relates to the provisional finding by the primary judge that, assuming Devcon had control over the relevant 'hazard', it had not been established at the trial that it would have been practicable for Devcon to have removed it. The particulars to that ground read as follows:
3.1The learned Judge erred in taking into account the alleged 'expertise' of the Kefo employees in determining whether or not the particularised 'solutions' were 'practicable'.
3.2Once the Respondent was a deemed employer, as a result of the operation of OSHA s 19(4), the scope of its duty was identical to that which an actual employer would have in the same situation under OHSA s 19(1).
3.3There is no situation in which an employer can rely entirely on the 'expertise' of its employees (ie the very persons to whom the employer owes that duty) as an answer to a charge that reasonably practicable steps were not taken.
3.4The case of Hamersley Iron Pty Ltd v Robertson … relied upon by the learned Judge provides no authority for a contrary conclusion. No analogy could be drawn between the third party expertise hypothesised in that case, and the supposed expertise of the Kefo employees. A 'non‑delegable' duty cannot be discharged by relying on the persons to whom it is owed; if it was possible to do so, then there would in fact be no duty owed.
3.5An employer is required to take into account the possibility of mistakes, inadvertence etc by employees in discharging its duty. The evidence clearly established such a 'mistake' by the deceased as to the adequacy of the measures taken to provide lateral restraint to the rafters in Unit 3.
3.6The prosecution also clearly established that the only third party called upon by the Respondent … was not engaged to address construction issues (cf Hamersley).
3.7The learned Judge also purported to take into account the 'reasonableness' of the Respondent's reliance on the Kefo employees, when the OSHA definition of 'practicable' provides no basis for an additional test of 'reasonable conduct'; ie additional to the criteria of the definition.
Once again, it is important to bear in mind that the case against Devcon, so far as it is presently relevant, is solely that it was practicable for it to have ensured, and it should have ensured, that there was adequate lateral restraint of the steel roof beams.
Assuming that Devcon had control over that 'matter' for the purposes of s 19(4) (in the necessarily wide sense that would then have to be accorded to the word 'control'), we are unable to accept that the evidence established that it was 'practicable' as defined, for Devcon to have ensured that there was adequate lateral restraint of the steel roof beams during the erection of the building under construction.
We have earlier referred to the definition of 'practicable'. It means 'reasonably practicable' having regard, where the context permits, to the severity of any potential injury and the degree of risk of it occurring; to the state of knowledge about the injury, the risk of it occurring and the means of removing or mitigating it; and to the availability, suitability and cost of the means of removing or mitigating it.
It can be accepted that the 'state of knowledge' referred to in this definition is objective. The fact that a person who is in control of a particular 'matter' affecting safety does not know something that should have been known by a person in that position cannot answer the question whether it was reasonably practicable for that person to have done something about the matter. However, the words 'state of knowledge about … the risk … and means of removing or mitigating the risk … ' encompass not only what is known concerning those matters, but also who might ordinarily be expected to have that knowledge. Consequently, when considering, for the purposes of s 19(1), whether it was reasonably practicable for a deemed employer to have avoided a particular hazard, it would be a relevant consideration that the expert knowledge required to avoid the hazard fell within the province of the specialist contractor which had been engaged to do the work that gave rise to the hazard and outside that of the deemed employer. In Morrison [22], Le Miere J said, in the context of s 22(1) of the Act, that in order to secure a conviction the prosecutor 'must prove either that the defendant actually knew of the risk of injury or harm to health occurring or that a reasonable person in the position of the defendant [our italics] would have appreciated or foreseen the risk … of the injury or harm to health occurring … '. It is important, also, to bear in mind that the definition of 'practicable' provided by s 3(1) requires regard to be had to the considerations there specified only 'where the context permits'.
This approach to the meaning of 'reasonably practicable' is consistent with that adopted by the court in Complete Scaffold Services. We have said that Doyle CJ (agreed with by the other members of the court) did not regard it as 'reasonably practicable' for the purposes of the similar legislation there under consideration, for the principal to supervise contractors 'in all the details of the performance of their work' [56]. We have mentioned that he said that one must consider what it was reasonably practicable for the principal to do 'as a deemed employer of [the worker] who was on site as a worker employed by a contractor, the contractor being hired to carry out specialised work for [the principal]' [57].
However, counsel for the appellant relied, in this context, on what was said by EM Heenan J in Tobiassen as follows [118] ‑ [124]:
In Chugg v Pacific Dunlop Ltd … there is … a clear dictum (at 260) in the reasons for decision of Dawson, Toohey and Gaudron JJ that 'overmuch significance' ought not to be given to 'the relative knowledge of an employer or an informant', because in many instances the questions of practicability do not involve special knowledge. Insofar as the reasons of Dawson, Toohey and Gaudron JJ adopted (at 262), with approval, the observations of Lord Upjohn in Nimmo v Alexander Cowan & Sons Ltd [1968] AC 107, 125‑ 126, it is also apparent that the duty, resting upon the employer or other person obliged to exercise care, is 'with his experts to consider the state of the place of work in all its circumstances and to take whatever steps he could, so far as reasonably practicable, to make it safe'.
Far from limiting the objective state of knowledge to the subjective state of knowledge of the particular builder (in the present case) or persons in comparable positions, the legislation, in my view, casts an obligation upon all persons, upon whom comparable duties are imposed, to acquaint themselves with practicable measures existing in the industry for the maintenance of safety and the avoidance of hazard. They will not be excused from a failure to perform this obligation simply because of the limits of their own subjective knowledge, except on occasions where, as Steytler J said in Hamersley Iron Pty Ltd v Robertson (Unreported, WASC, Library No 980573, 2 October 1998), it is knowledge of a special kind attributable to a specialised contractor and outside the scope of the knowledge to be expected of a builder. I must say, with all respect, that I have hesitations in limiting the scope of practicability even to that extent, because the definition of 'practicable' within s 3 of the Act speaks about 'state of knowledge' in the broad, without limiting the state of knowledge to any particular trade, profession or occupational experience. This is consistent with the policy of the Act which, in my view, is intended to achieve a situation that if, objectively speaking, there is known within an industry that there are hazards of a particular kind which may be injurious to the health and welfare of persons on worksites, and that there are means available of avoiding or reducing those hazards, then, having regard to factors such as the degree of risk, the means of removing or mitigating the risk and the availability, suitability and the cost of the means to reduce the risk, the decision about practicability will then be taken in a balanced and objective fashion.
The crucial point of this statutory language, however, is that it lends no support at all to a view of practicability which is associated with a limited knowledge by some person within the industry who, by hypothesis, is oblivious to the existence of objective knowledge within the industry which identifies the risk and suggests means of addressing it. Certainly, there is a balancing judgment to be made, having regard to the degree of risk involved, the means available of reducing the risk and the associated costs, but that balancing exercise needs to be performed once it is established that there is an objective state of knowledge within the industry which exposes the hazard and suggests a means of coping with it. That state of knowledge is not limited to occasions when the risk is known and appreciated at lower levels, or by the individual on whom the duty is cast.
As framed, the obligation requires persons on whom such duties are cast to acquaint themselves with the objective state of knowledge within the industry and, as implied by Lord Upjohn in his remarks in Nimmo v Alexander Cowan & Sons Ltd, to take advice from experts and others to supplement his or her own appreciation of the situation. Failure to do that does not displace the existence of an objective state of knowledge or excuse a failure to perform the duty if, otherwise, it were practicable to perform it. This is, if I may say so with respect, the essential error which pervades this aspect of the decision at first instance; namely, to associate the objective state of knowledge with the scope of knowledge actually possessed or to be expected of such a builder. In my view, that significantly understates the extent of the statutory and regulatory duties here under consideration. In Hamersley Iron Pty Ltd v Robertson, Steytler J expressly contemplated that in relation to a personal duty to provide a safe workplace, so far as is practicable, that latter phrase determines the extent of the obligation:
'If that, in turn, requires the employer to call upon expertise which it does not itself have then there is no reason why it should not do so and, indeed, every reason why it should (20)'.
Indeed, it was accepted in Hamersley Iron Pty Ltd v Roberston, as following from Ertech Pty Ltd v Reid (Unreported, WASC, Library No 9174, 6 December 1991), that the state of knowledge which forms part of the component of practicability, is that possessed by persons generally who are engaged in the relevant field of activity and not the actual knowledge in fact possessed by a specific employer in particular circumstances. See, also, Pullin J in Silent Vector Pty Ltd v Shepherd [[2003] WASCA 315] [12].
This is entirely consistent with the legislative policy to bring work safety standards into compliance with objective safety criteria known to industry as a whole, rather than to define the duty and measure the obligation with reference to the variable standpoint of an individual self-employed person, employer or employee, or other persons filling those positions who might only have a limited appreciation of the objective standards available within the industry as a whole. Lest this appear too onerous, or indifferent to hitherto prevailing standards of the uninformed, it can be said that it means no more than that a reasonable employer, employee or self-employed person in any of the positions postulated by the Act, will be a person who is informed and cognisant of the objective standards of dealing with hazards existing within the industry in which he or she may be working, even though this may require that person to seek advice from experts or others better informed than himself or herself so as to become acquainted with that objective standard.
Consequently, in the present prosecutions, once the learned magistrate was satisfied, as he was, that objective knowledge did exist within this industry about the hazard presented by torsional forces operating on steel rafters without adequate lateral restraint, and that means were available of dealing practicably with that risk, it was wrong to find that the measures which the prosecution asserted should have been taken by the respondent, in the first, second and third charges, were not practicable.

Nothing said by EM Heenan J in these paragraphs (and we should mention that he appears not to have been referred to Complete Scaffold Services) causes us to doubt the conclusions at which we have arrived in the context of s 19(1) of the Act. We endorse what was said by Steytler J in Hamersley Iron.
That case concerned s 9(1)(a) of the Mines Safety and Inspection Act 1994 (WA), which provided that 'An employer must, so far as is practicable, provide and maintain at a mine a working environment in which that employer's employees are not exposed to hazards … '. The word 'practicable' was defined in s 4 of that Act in terms that are relevantly identical to the definition that applied in this case. As will be apparent, in the extract from the judgment of Steytler J quoted and applied by the primary judge in this case, Steytler J said that, if the obligation to provide a safe workplace requires an employer to call upon expertise that it lacks, then it should do so. However, he added that, if the employer had relied upon a specialist contractor to perform a task which demonstrably fell within its area of expertise and outside that of the employer, and if the task reasonably appears to the employer (who has such knowledge of the matters specified in the definition as might be expected to be had by employers of its kind) to have been carefully and safely performed by the specialist contractor, it would ordinarily be difficult to conclude that the employer had breached the duty put upon it by the Act.
That construction seems to us to be appropriate. In our respectful opinion, a construction imposing a greater burden on an employer of the kind there under consideration would be unreasonable and unsupported by the language of the section, read in its context. For the reasons we have given, the same appears to us to be true of s 19(1) of the present Act (read with the definition of 'practicable' in s 3(1)).
We should add that nothing said by Dawson, Toohey & Gaudron JJ in Chugg v Pacific Dunlop Ltd (1990) 170 CLR 249, 260 seems to us to be inconsistent with the construction we have adopted. The court was there concerned with s 21(1) of the Occupational Health and Safety Act 1985 (Vic), which required an employer, 'so far as is practicable' to provide and maintain a safe working environment. 'Practicable' was defined as 'practicable having regard to ‑ (a) the severity of the hazard or risk in question; (b) the state of knowledge about that hazard or risk and ways of mitigating or removing that hazard or risk; (c) the availability and suitability of ways to remove or mitigate that hazard or risk; and (d) the cost of removing or mitigating that hazard or risk'. What was said by Dawson, Toohey & Gaudron JJ in the passage referred to by EM Heenan J was that overmuch significance should not be given to the relative knowledge of an employer and an informant (who may have superior knowledge than an employer on some matters bearing on the question of practicability) because, in many cases, questions of safety and practicability raise issues of common sense rather than special knowledge. Plainly, where that is so the difference in knowledge will have no bearing on the question of practicability or, under the Western Australian Act, that of reasonable practicability. However, as we have said, that was not proved to have been the position in this case.
Also, the adoption by Dawson, Toohey & Gaudron JJ (262) of what was said by Lord Upjohn in Nimmo v Alexander Cowan & Sons Ltd [1968] AC 107, 125 ‑ 126, to the effect that (under s 29(1) of the Factories Act 1961 (UK)) it is the duty of an employer 'with his experts to consider the state of the place of work … and to take whatever steps he can, so far as reasonably practicable, to make it safe', seems to us, with due respect, to say nothing about a circumstance in which a principal engages specialist contractors to do work in respect of which the principal lacks the requisite expertise and in which questions of safety and practicability are not matters of common sense rather than specialised knowledge.
As Stuart‑Smith LJ said in R v Associated Octel Ltd [1994] 4 All ER 1051, 1063 (approved by the Victorian Court of Appeal in R v ACR Roofing Pty Ltd [2004] VSCA 215; (2005) 11 VR 187 [68]):
… the question of control may be very relevant to what is reasonably practicable. In most cases the employer/principal has no control over how a competent or expert contractor does the work. It is one of the reasons why he employs such a person ‑ that he has the skill and expertise, including knowledge of appropriate safety precautions which he himself may not have. He may be entitled to rely on the contractor to see that the work is carried out safely, both so far as the contractor's workmen are concerned and others, including his own employees or members of the public; and he cannot be expected to supervise them to see that they are applying the necessary safety precautions. It may not be reasonably practicable for him to do other than rely on the independent contractor.
But there are cases where it is reasonably practicable for the employer to give instructions how the work is to be done and what safety measures are to be taken …
The question of what is reasonably practicable is a matter of fact and degree in each case.
We should add that, contrary to the contention advanced on behalf of the appellant, the construction that we prefer would not have the consequence that a non‑delegable duty imposed by the Act would be discharged by relying upon the persons to whom it is owed (and it is important to bear in mind that, in this context, those persons are 'deemed … employees' and not actual employees of the principal). The consequence of that construction is only that, in circumstances such as those in this case, no duty of the kind contended for is imposed by the Act.
Ground 3 consequently fails.

Conclusion

The appeal should be dismissed.