C.A. Clarifies Causation Rules in Negligence Cases

In a 2-1 decision, the Court of Appeal allowed an appeal in a medical malpractice case, finding in favour of the defendants. The decision hinged on what evidence a plaintiff must lead in order to show that the defendant’s negligence caused (or “materially contributed to”) her injury. The Court’s reasons illustrate how the issue of causation is to be addressed in cases in which a plaintiff cannot show that “but for” the defendant’s negligence, the injury would not have occurred.

The case was Aristorenas v. Comcare Health Services and Dr. Jeffrey Gilmour. The plaintiff developed necrotizing fasciitis (“flesh-eating disease”) after delivering a baby by Caesarean section. She had been treated, over an ensuing period of two weeks, by the defendants.

At trial, Justice Sidney Lederman had found that both defendants had been negligent and he assessed damages of $50,000. The defendants did not appeal either the findings of negligence or the assessment of damages. Their appeal was limited to the issue of causation. The defendants argued that the trial judge had erred in concluding that the defendants’ negligence had caused the necrotizing fasciitis. Two of the three members of the panel that heard the appeal agreed.

At trial, Justice Lederman had found that necrotizing fasciitis was one possible outcome of an infected wound being left untreated, but that “whether or not necrotizing fasciitis would have otherwise developed in the plaintiff is not a matter susceptible of scientific proof and none was led by any of the parties”. His Honour felt that, in the absence of such evidence, he could not find that causation had been established on the traditional “but for” test. Instead, he elected to apply the “robust and pragmatic approach” to causation that had been endorsed by the Supreme Court of Canada in Snell v. Farrell.

He considered the fact that the fasciitis had developed in the same location as the untreated wound and had been discovered near the time that the defendants were treating the plaintiff. This led Justice Lederman to say that, “as a matter of common sense I conclude that the plaintiff has established, on a balance of probabilities, that the defendants’ negligence materially contributed to the injury”.

In the Court of Appeal, Justice James MacPherson would have upheld the trial decision. For one thing, he felt that the appellants had fallen far short of demonstrating “palpable and overriding error” on the part of Justice Lederman. But further, he agreed with the way in which the trial judge had analyzed causation.

The majority (Justices Paul Rouleau and Marc Rosenberg) felt that while the trial judge had been right to apply the “robust and pragmatic approach” to causation, he had erred in his “articulation and application of that test”. There was, they believed, insufficient evidence to support a finding that the necrotizing fasciitis had been caused by the defendants’ negligence. The reasons of the majority are important, as they are the latest appellate guidance on the difficult subject of causation. The highlights of those reasons appear below:

  • the two approaches to causation that have been sanctioned by Canadian courts are the standard “but for” test and the “material contribution” test, the latter to be employed in cases where the “but for” test is unworkable, for one reason or another;
  • both tests require the court to apply a “robust and pragmatic approach, but this test is to be applied to the evidence. It is not a substitute for evidence;
  • the “material contribution” test is to be used in “cases that involve multiple inputs that all have harmed the plaintiff. The test is invoked because of logical or structural difficulties in establishing ‘but for’ causation, not because of practical difficulties in establishing that the negligent act was a part of a causal chain”;
  • while causation need not be established “with scientific precision”, there must still be evidence “and other considerations that, when viewed pragmatically and robustly, would satisfy a trier of fact on a balance of probabilities that there was causation”;
  • the Court pointed to the Supreme Court’s decision in Snell, to the effect that it is not sufficient for a plaintiff to prove that the defendant’s negligence created a risk that the injury would occur.

In this case, the majority felt that a vital element was missing from the trial judge’s causation analysis. Even if it were assumed that there is a link between delayed treatment (alleged against the defendants here) and the development of necrotizing fasciitis, there was no evidence here to show what the effect of the delay in this case had been. Other possible explanations had not been ruled out: “There are many theories of causation, and the evidence leaves us in a position where we do not know which one is correct or the most probable. None of the evidence provided by the parties provides a link between the negligence of the defendants and the harm suffered by the plaintiff….Eschewing scientific certainty does not eliminate the need for any evidence to support causation. If causation can be inferred in the absence of any proof, then it is indistinguishable from reversing the burden of proof, something Sopinka J. clearly disapproved of in Snell.”

In the result, the Court of Appeal reduced the plaintiff’s award from $50,000 to $1,000 (given that the findings of negligence were unchallenged on appeal).

The case reminds us, that despite the “material contribution” theory of causation endorsed by the Supreme Court in Athey v. Leonati, ultimately, the plaintiff must lead evidence that allows the court to infer, on a balance of probabilities, that there is a causal link between the injury and the defendant’s actions.

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