Causation in Negligence Actions: Supreme Court of Canada Limits Application of Material Contribution to Risk Test by Alan Melamud

The Supreme Court of Canada recently revisited the issue of the appropriate test for causation in negligence actions in its decision Clements v. Clements.  Confirming that the test for causation is the “but for” test, the Court went further to circumscribe the application of the one exception, the material contribution approach, to limited circumstances involving multiple tortfeasors.  The “but for” test requires that a plaintiff demonstrate on a balance of probabilities (50%+1) that absent the defendant’s negligent act, the injury suffered would not have occurred.  The material contribution test, to the contrary, requires that the plaintiff show only that the defendant materially contributed to the risk of the plaintiff’s loss, which poses the risk fixing the defendant with liability although it may not be responsible for any injury.  The latter test, therefore, contravenes the fundamental principle of tort law of holding defendants responsible only for injuries they cause.

The Court’s strengthening of the requirement that plaintiffs show that a particular defendant’s negligence was necessary to bring about their injury may appear to be good news for defendants.  The Court however, also reiterated that courts can apply a robust and “common sense” approach to the test, softening the burden plaintiffs must meet.

Traditionally, the material contribution test has been applied in “special circumstances” where a court felt that fairness demanded that the plaintiff be allowed to prove its case on the lower standard.  In its 2007 decision on causation, Resurfice Corp. v. Hanke, the Supreme Court explained that “special circumstances” refer to those situations where: (1) it would be “impossible” for the plaintiff, for reasons outside its control, to prove causation on the “but for” standard; and (2) the defendant unjustifiably exposed the plaintiff to the risk that materialized and caused the loss.

For defendants, this meant that they would be exposed to liability where the limits of understanding an accident after the fact, or the limits of our scientific knowledge, made it “impossible” for the plaintiff to show a defendant’s negligent act actually caused the loss.

In Clements, the Supreme Court of Canada changed all that.  The Court restricted the concept of “impossible to prove” to where there are multiple tortfeasors that caused the loss, viewed globally, but each are able to blame the other making it impossible for the plaintiff to show on the “but for” standard which one is truly responsible.  This would not apply to multiple tortfeasor situations where the plaintiff could show that one or more of the defendants’ negligence was a necessary cause of the injury.  In addition, while not closing the categories of where the material contribution test might apply, the Court did practically foreclose its application where there is only a single tortfeasor.

Significantly, the Court explicitly rejected providing an exception to the “but for” standard where logical/conceptual or factual/scientific limitations make proving causation “impossible”.  The Court reasoned that such situations arise where the plaintiff has simply failed to meet his or her burden or is hamstrung by limitations in technology or scientific understanding.  Consequently, these situations do not warrant undermining the principle of fault that underlies tort law. 

The Court effectively shifted the problem of limitations in factual or scientific knowledge from defendants on to plaintiffs.

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