40 In WorkCover Authority of New South Wales (Inspector Patton) v Fletcher Constructions Australia Limited (2002) 123 IR 121 the Full Bench considered the requirements of s 53 as follows:
83 There was no question that the respondent had the requisite control over the worksite and, therefore, s53(b) does not arise. Rather, the respondent submitted it had done all that was reasonably practicable. As to what is required when considering a defence under s53(a), regard should be had to the judgment in WorkCover Authority of New South Wales (Inspector Byer) v Cleary Brothers (Bombo) Pty Ltd (2001) 110 IR 182:
[87] It is evident from these authorities that what is required by s53(a) of the Act is a balancing of the nature, likelihood and gravity of the risk to safety occasioning the offence with the costs, difficulty and trouble necessary to avert the risk. At one end of the scale, it could not be reasonably practicable to take precautions against a danger which could not have been know to be in existence: see Jayne v National Coal Board [1963] 3 All ER 220 at 224 and Shannon v Comalco Aluminium Ltd at 362. Similarly, if the happening of an event is not reasonably foreseeable then it will not generally be reasonably practicable to make provision against that event: see WorkCover Authority of NSW (Inspector Mayo-Ramsay) v Maitland City Council (1998) 83 IR 362 at 381; WorkCover Authority of NSW v Kellogg (Aust) Pty Ltd at 259 and Austin Rover Ltd v Inspector of Factories at 627 per Lord Goff and at 635 - 636 per Lord Jauncey of Tullichettle.
[88] At the other end of the scale, there will be cases, such as the present, in which known or obvious risks to safety exist. In these circumstances, the defendant will not have established a defence under s53(a) of the Act where it was reasonably practicable to have complied with the Act by ensuring that persons were not exposed to those risks. This may be the case because no measures were reasonably available or because measures which were available were not reasonably practicable. As has been discussed, the assessment of the reasonable practicability of those steps requires a balancing of the quantum of the risk with the sacrifice (in money, time and trouble) in adopting the measures necessary to avert the risk. In my view, where there is a known risk which entails the potential for serious injury to persons in the workplace, the defendant will generally have to demonstrate that the costs, difficulty or trouble occasioned by the measures significantly outweigh the risk. This must be done by reference to the charge as brought by the prosecutor.
84 Those passages were subsequently approved by the Full Bench in Legge v Coffey Engineering Pty Ltd (No 2) (2001) 110 IR 447 at [38] and in Bultitude v Grice at [71].
85 It may well arise that due to the exigencies of a particular work situation, it may have been impractical to have developed a safe system of work in advance. The particular circumstance may not have been a matter that was reasonably foreseeable in the way that phrase has been used in the authorities: see Bultitude v Grice (at [68]):
Reasonable foreseeability of a risk or detriment to safety is relevant to the extent that it assists in determining whether it was reasonably practicable to avoid the risk.
86 Regard should be had in this respect to the judgment in Kellogg (No.1) (adopted by the Full Bench of the Court in Kennedy-Taylor v WorkCover Authority (at 82), Genner Constructions (at [67] - [68]) and Bultitude v Grice (at [68])):
To establish a defence under s53, the defendant must prove, to a civil standard, either that it was not reasonably practicable to comply with the Act or that the commission of the offence was due to causes over which the defendant had no control and against the happening of which it was impracticable to make provision: see Drake at 48-49; Sydney City Council v Coulson (1987) 21 IR 477 at 480; and Italo Australian Construction Pty Limited v Parkes (1988) 24 IR 428 at 431. So much was accepted by the defendant in this case.