As I predicted in AILA News following my paper delivered at last year’s national conference, the High Court has handed down two important decisions shaping the law on causation. The cases are Amaca Pty Ltd & Ors v Ellis HCA 5/2010 and Tabet v Gett HCA 12/2010.

Each decision was unanimous and involved plaintiffs seeking to establish a defendant’s liability although the probability the defendant’s breach caused the loss was less than 50%. 

In Ellis, the deceased was a smoker who had been exposed to asbestos and contracted lung cancer. Although experts’ views differed on the range of probabilities for each risk factor, each agreed the risk of smoking having caused the cancer was significantly greater than the risk of asbestos exposure, in isolation or in combination with cigarette smoke.

The High Court observed there was no evidence to show smoking and asbestos must work together and the probability or chance the deceased’s cancer was caused by exposure to asbestos (either in isolation or in combination with smoking), did not exceed 23%. In contrast, the risk factor contributable to smoking alone ranged from 67% to 92%. To then describe exposure to smoking and asbestos as more dangerous than exposure to smoking alone was, in the court’s view, ill founded.

In the absence of direct evidence on the cause of the deceased’s cancer, it was necessary for the plaintiff to establish the case should be treated as conforming to the pattern described by epidemiological studies.

Available epidemiological evidence showed smoking was more probably than not, the cause of the cancer and the risks and probabilities associated with the asbestos exposure were low and insufficient to found an inference exposure to respirable asbestos fibre was a cause.

Questions of material contribution arise only if a connection between the deceased’s inhaling of asbestos and developing cancer was established. Knowing that inhaling asbestos can cause cancer does not entail that in this case it probably did.

The decision’s practical implication is that in claims involving more than one cause of injury, it will be necessary for plaintiffs to establish that a particular negligent cause by a particular defendant was, more probably than not, the cause of the injury.  Plaintiffs will no longer be able to rely on loose inferences of logic based on purported material contributions. The High Court distinguished the application of the UK line of authority relating to asbestos exposure, rather than saying it was wrong or they would not follow it.

Tabet’s case considered causation and the law of medical negligence. 

The plaintiff, 6, was suffering headaches, nausea and vomiting and was admitted to hospital under the defendant’s care.  At trial, the defendant was found negligent in not ordering a CT scan.  A day later, the plaintiff suffered a seizure.  A CT scan on that day revealed Tabet had a brain tumor. She suffered irreversible brain damage, 25% of which was caused by the increased intracranial pressure between the time the scan should have been ordered and it being undertaken.

Had a scan been administered earlier, there was an increased chance Tabet would have avoided some of the brain damage. The trial judge assessed that at 40% and the Court of Appeal at no greater than 15%. 

Relying on decisions of the Victorian Court of Appeal in Gavalas v Singh and the NSW Court of Appeal in Rufo v Hosking, the trial judge awarded the plaintiff 40% of assessed damages.

The NSW Court of Appeal declined to follow the two earlier decisions, including its own, and found the loss of a 40% chance of a better medical outcome did not constitute the required “damage” for a cause of action in negligence.

As the plaintiff only established a loss of a 40% chance of a better outcome, the plaintiff could not prove, on a balance of probabilities, the respondent’s negligence caused her damage.

All six High Court judges who heard the case (Chief Justice French did not) held that to allow a plaintiff to recover compensation in negligence actions for only the loss of a chance of a better medical outcome, would diminish the requirement for a plaintiff to prove, on the balance of probabilities, that his/her damage was caused by a defendant’s negligence.

The plaintiff was unable to prove that, had treatment been undertaken earlier, the brain damage would have been avoided. The evidence was insufficient to be persuasive. The requirement of establishing causation is not overcome by redefining the mere possibility that such damage as did occur, might not eventuate as a chance and then saying it is lost when the damage actually occurs. Such a claim could only succeed if the standard of proof were lowered, which would require a fundamental change to the law of negligence.

The decision is likely to have broad impact in personal injury claims, although the court made it clear it does not affect claims for loss of chance in economic loss claims, thus the decision in Sellars v Adelaide Petroleum NL HCA 4/1994 remains good law.

David McKenna 

AILA President