“The Court of Appeal reversed in two sets of concurring reasons. Kasirer, J.A., writing for the majority, held that the trial judge erred in law in failing to apply an “unfavourable inference” of causation against the defendants. The “unfavourable inference”, first set out by the Supreme Court in Snell v. Farrell,  2 S.C.R. 311 and confirmed in a Quebec medical malpractice setting in St. Jean v. Mercier,  1 S.C.R. 491 provides that in certain cases, “very little affirmative evidence on the part of the plaintiff will justify the drawing of an inference of causation in the absence of evidence to the contrary” (Snell, p. 329).