Proving causation on the basis of an adverse inference in medical malpractice claims.
by Chris Wullum
In the realm of medical malpractice lawsuits, one of the most important, and at times, most difficult issues for a plaintiff to establish is the legal element known as causation. In order to succeed with a medical malpractice claim, not only must the plaintiff prove that the doctors or nurses fell below the standard of care in the provision of their medical services, the plaintiff must also establish, on a balance of probabilities, that the breach of the standard of care was the legal cause of the person’s injuries.
But For Test
The longstanding legal test for proving causation in Canada has been expressed as requiring the plaintiff to show that but for the actions or conduct of the defendant, the plaintiff would not have suffered the harm or injury. This has come to be known as the “but/for test”.
With the onus placed on the plaintiff to meet this legal test for establishing causation, there can often be circumstances that arise in the complex arena of medical science whereby having available evidence to meet this burden can be a challenge for a plaintiff.
Adverse Inference of Causation
Of particular interest to lawyers who practice medical malpractice law, the Supreme Court of Canada recently issued its decision in the case of Benhaim v. St.-Germain,  2 SCR 352, in which the Court discusses the concept of when a Court may draw an adverse inference of causation against the defendants where the facts available to prove causation lie particularly or uniquely within the knowledge of the defendants.
The claim in Benhaim v. St-Germain was pursued by the estate of an otherwise seemingly healthy middle aged non-smoker who was diagnosed with stage 4 lung cancer and ultimately passed away from the disease. The case was advanced on the basis that if the lung cancer had been diagnosed earlier, it would have been at a stage that was more treatable, and from which the defendant would more likely than not have been cured. The trial judge in Quebec found against the plaintiff’s claim on the basis that the plaintiff had not convinced her that but for the delay in diagnosing the cancer, the plaintiff would likely have survived. The Quebec Court of Appeal however, reversed this decision of the trial judge and stated that an adverse inference of causation arose against the defendants when two criteria were established.
Those criteria were, firstly, that the defendant physician’s negligence undermined the plaintiff’s ability to prove causation, and secondly, that the plaintiff had adduced at least some affirmative evidence of causation. Once these points were established, it would be open to the defendant to rebut the inference of causation by leading evidence to the contrary. In this fashion, the Quebec Court of Appeal was drawing from the Supreme Court of Canada’s discussion of causation from Snell v. Farrell,  2 SCR 11 and St-Jean v. Mercier,  1 SCR 491 where the Court noted that in many medical malpractice cases, the defendant is often in a better position than the plaintiff to determine the cause of the injury and that in such cases, very little affirmative evidence on the part of the plaintiff would be required to justify the drawing of an adverse inference of causation in the absence of evidence to the contrary.
Of particular note in Benhaim v. St-Germain, the affirmative evidence of the plaintiff included statistical evidence that 78% of cancers found fortuitously (as was the situation for the plaintiff) are at stage 1 and that such a stage has a 70% cure rate.
Supreme Court Decision
This Quebec Court of Appeal decision was appealed to the Supreme Court of Canada, and in a split decision, the Supreme Court overturned the Court of Appeal and instead deferred to the trial judge’s factual analysis on causation stating that a decision as to whether to apply an adverse inference of causation is to be done on a purely discretionary basis as determined by the trier of fact based on all of the available evidence.
The important legal point on causation made by the Court in this decision, is that the trier of fact is not mandated to draw an adverse inference of causation in medical liability cases whenever the defendant’s negligence undermines the plaintiff’s ability to prove same and the plaintiff has adduced at least some evidence of causation. It is a purely discretionary inference that the Court is permitted to draw (not one that it is required to draw) where these factors may exist.
Further, while the Supreme Court stated that the a trier of fact may take statistical evidence into account when determining causation, it cautioned on the use and weight to be given to statistics stating that their probative value will vary according to factors such as methodology, how clearly the statistics reveal a trend, and the resemblance between the underlying conditions related to the statistics and the condition of the plaintiff. So while statistical evidence can be used in establishing causation in a case, without an evidentiary bridge to the specific circumstances of the plaintiff in the case, statistical evidence in and of itself may be of limited value.
Reconfirming the adverse inference principle
While the Supreme Court’s decision may limit the seemingly strict application of the adverse inference of causation suggested by the Quebec Court of Appeal, it does still reconfirm that such an argument on causation may be applicable in cases where the relevant factors are found to exist. One might surmise however that it will be applied infrequently in cases and that the “but/for test” will continue to be the necessary standard of proof in most medical malpractice cases. As such, it is still important as always in medical malpractice cases to develop medically based proof of causation.
If you require advice on a medical malpractice issue, please contact a lawyer from our Medical Malpractice Practice Area at Tapper Cuddy LLP.