Proving Causation in Medical Malpractice Cases – Sienkiewicz v. Greif

Biggest Hurdle?

The biggest challenge a plaintiff in a medical malpractice case usually faces is proving, on the balance of probabilities, that the defendant’s actions (or inaction) caused the plaintiff’s injuries.

Biological vs. Legal Cause

A recent case from the House of Lords in the United Kingdom examines the issue of causation in a wrongful death case and discusses the difference between the “biological cause” of death or injury and “cause in law”.

Although the decision is not binding on the courts here in Canada, the reasoning in the case is helpful for anyone who has to deal with the issue of causation in medical malpractice cases.

In Sienkiewicz v. Greif the court had to consider whether exposure to asbestos caused the death of Enid Costello.

Lord Phillips stated at paragraph 6:

“Methods of Proving Causation

Most claims for death or personal injury result from accidents. In such cases the cause of death or personal injury will seldom be in issue. A body of knowledge which I shall call “medical science” will enable a witness, expert in that science, to describe the precise mechanism by which the accident brought about the death or injury. I shall describe this as the “biological cause” of death or injury. It is sometimes referred to by the more general description of the “cause in fact”. In some cases, however, medical science will not yet have identified the precise mechanism by which an injury gives rise to a particular physical consequence. In such cases it may be possible to deduce that there was a causative link between the two by evidence of what usually happens. Epidemiological evidence that a particular injury or disease usually follows a particular type of bodily insult may enable a court to conclude in a particular case, on balance of probability, that the former was caused by the latter. “Post hoc ergo propter hoc”. A finding of causation based on such evidence is sometimes described as “the cause in law”.”

Lord Phillips’ decision examines the rule of epidemiological evidence in wrongful death cases and discusses whether proof that the defendant’s actions “doubled the risk” of death is the same as proving on the balance of probabilities that the defendant’s actions caused the plaintiff’s death.

Doubling the Risks

The court explained the “doubles the risk” test as follows:

“The “doubles the risk” test is one that applies epidemiological data to determining causation on balance of probabilities in circumstances where medical science does not permit determination with certainty of how and when an injury was caused. The reasoning goes as follows. If statistical evidence indicates that the intervention of a wrongdoer more than doubled the risk that the victim would suffer the injury, then it follows that it is more likely than not that the wrongdoer caused the injury.”

Lord Phillips concluded that:

“Where there are competing alternative, rather than cumulative, potential causes of a disease or injury … I can see no reason in principle why epidemiological evidence should not be used to show that one of the causes was more than twice as likely as all the others put together to have caused the disease or injury.”

Epidemiological Evidence and Causation

The court eventually went on to reject the epidemiological evidence with respect to causation in the plaintiff’s case. However, the case does provide helpful direction to plaintiff medical malpractice lawyers who want to use epidemiological evidence to prove causation in medical malpractice claims.