Coote v S & P Jackson Pty Ltd  NSWCA 385 considered the following issues:
- The requirement for a Court to reach "a definite conclusion affirmatively drawn" for a finding of negligence.
- When considering competing theories of causation one must emerge as more likely than the other as opposed to equally likely.
In this Alert, Senior Associate Brooke Jacobs and Solicitor Abbey Wilkinson consider how the courts will approach causation in negligence when there are competing expert opinions.
The plaintiff was working as a plant operator clearing a blocked dust extraction 15 metres above ground.On 17 June 2006, he was working from a workbox lifted into place by a 15 tonne Tadano crane.The Tadano crane and crane operator had been hired by the plaintiff's employer from the defendant.When the crane operator adjusted the height of the workbox holding the plaintiff about 30 to 45 minutes into the job, it unexpectedly fell 15 metres to the ground below and the plaintiff suffered significant injuries.
The plaintiff commenced proceedings against the defendant claiming damages for negligence for failing to maintain the crane.The plaintiff also commenced proceedings against the defendant under the Motor Accidents Compensation Act 1999 (NSW) (MACA).
The decision at first instance
At first instance, the trial judge found that the defendant was not liable in negligence and that the plaintiff's claim under the MACA failed because his injuries were not sustained in a "motor accident".The plaintiff appealed the decision of her honour in relation to the negligence action only.
The decision on appeal
Both the plaintiff and the defendant obtained expert evidence regarding the cause of the crane failure and freefall of the workbox.
The plaintiff's expert maintained that the clutch selector valve in the crane failed, causing catastrophic loss of hydraulic pressure in the clutch. The expert attributed this failure to wear affecting the valve. The wear was evident on dismantling the clutch unit post accident.
The defendant's expert agreed that the hydraulic pressure in the clutch had failed, although he considered that it happened very rapidly (within a second or less). He considered that the more likely cause of the workbox entering sudden freefall after 30 to 45 minutes of work was a contaminant the size of a pinhead lodging itself in the clutch.
Also in evidence was a report by Safe Cranes Pty Ltd that the crane had been stripped down and reassembled in 2007, using the same clutch parts, and had been in use since that time without further incident. It was, however, conceded that an accumulator had now been fitted which helped to maintain hydraulic pressure in the clutch.
The defendant's expert gave evidence that the occurrence was a rare unforeseeable event. In cross examination, the plaintiff's expert conceded that any wear would only have been detected on the 10 or 25 year service when the clutch would be removed and dismantled. The crane was 24 years old at the time of the incident and the plaintiff's expert accepted that any wear may not have been detectable at the time of the 10 year service.
The Court of Appeal observed that an examination of the issue of negligence must be preceded by a consideration of what caused the accident.
Referring to the decision in Jones v Dunkel  HCA 8), the Court of Appeal observed that:
'In examining an issue which provides the foundation for a finding of negligence, it is necessary for the Court to reach "a definite conclusion affirmatively drawn". It is not enough if the evidence gives rise only to conflicting inferences of equal degree of probability so that the choice between them is a mere matter of conjecture.'
The Court of Appeal ultimately preferred the evidence of the defendant's expert because he was able to point to a specific reason for the freefall of the workbox whereas the plaintiff's expert could only account for the failure and not the sudden nature of it.
The Court of Appeal otherwise held that, on neither theory of causation was causative negligence proved. On the defendant's theory, the event was unforeseeable. On the plaintiff's theory, any wear would only have been detected on the 10 or 25 year service and a reasonable person in the position of the defendant would not have taken any further or other precautions.
The plaintiff's appeal was dismissed.
- In the case of catastrophic machinery failure, expert engineering evidence as to the cause can exculpate the defendant - particularly if the evidence can demonstrate that a reasonable person in the position of the defendant would not have taken steps to identify the potential for failure before it occurred.
- In a contest between expert theories on how an accident occurred, one theory must emerge as more likely than the other in order to satisfy the civil burden of proof "on the balance of probabilities".
- For a finding of negligence, a Court must reach a definite conclusion in relation to causation and not engage in mere conjecture.
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