Canada: Supreme Court Of Canada Clarifies Test For Causation In Negligence Cases

On June 29, 2012, the Supreme Court of Canada released its decision in the case of Clements v Clements.1 The majority decision, written by Chief Justice McLachlin, clarifies the analytical approach for determining causation in a negligence context – specifically, when courts should apply the traditional "but for" test versus the "material contribution" test.

Though Clements is a motor vehicle injury case, the Court's analysis may have widespread application to circumstances where a plaintiff alleges loss due to the negligent conduct of two or more defendants.

What are the potential tests for causation in negligence?

Canada's highest court confirmed that in order to establish liability in negligence, a plaintiff must prove that a defendant's negligent conduct was a material cause of the loss suffered. Typically, this is accomplished using the "but for" test, whereby the plaintiff must establish that the loss would not have occurred absent the defendant's negligence. However, in exceptional cases, a lower standard of causation known as the material contribution test may apply. Using this standard of causation, the plaintiff need only establish that the defendant materially contributed to the risk of the loss occurring. The majority decision in Clements clarifies the parameters for employing the material contribution test versus the "but for" test.

Facts of the case before the Court

In this case, the plaintiff, Mrs. Clements, sued her husband, Mr. Clements, for negligence arising out of a motor bike accident. Though Mr. Clements acknowledged negligence in driving the overloaded bike too fast in rainy conditions, he denied that his conduct caused the accident and related injuries sustained by his wife. Mr. Clements put forward expert evidence at trial that a nail puncture to the rear bike tire and resulting tire deflation most likely caused the accident. The trial judge rejected the defence expert's opinion, while also finding that the limitations of reconstruction evidence prevented the plaintiff from establishing liability on a "but for" standard. The trial judge went on to determine that it was appropriate to substitute the material contribution test, and found Mr. Clements liable for his wife's injuries.

On appeal, the British Columbia Court of Appeal overturned the trial judge's decision on the basis that the plaintiff had not met her burden in establishing causation on a "but for" standard and that reliance on the material contribution test was inappropriate in such circumstances.

A majority of the Supreme Court of Canada (Justices LeBel and Rothstein dissenting) overturned the Court of Appeal's decision and ordered a new trial. The majority agreed with the Court of Appeal that a material contribution test should not have been applied in this case. At the same time, the Court found that the trial judge had erred in requiring scientific proof of causation, rather than relying on a pragmatic, common-sense approach in applying the "but for" test. The dissenting Supreme Court justices agreed with the majority's causation analysis, but found that there was no basis to overturn the Court of Appeal's dismissal and require a second trial.

When is the "material contribution" test applied?

The Supreme Court expanded on earlier decisions addressing the material contribution test for causation. The Chief Justice identified the need for a "clear picture" as to when the "but for" test may be replaced by material contribution. The following special conditions were then set out by the Court as providing the basis for application of the test:

  1. The plaintiff can establish that she suffered a loss that would not have occurred "but for" the negligence of two or more defendants.
  2. While each defendant may, on their own, have caused the plaintiff's loss, the plaintiff cannot establish that any one defendant was the "but for" cause of her injury.
  3. As each defendant can point to another defendant as the possible "but for" cause of the plaintiff's injury and loss, thereby defeating a finding of liability, fairness and justice demand recourse to an alternative test for causation.

The Court repeatedly emphasized that the material contribution test should be employed rarely, as negligence law is anchored in "corrective justice that makes the defendant liable for the consequences, but only the consequences, of his negligent act."

Further, and perhaps most significantly, the Court all but eliminated application of the material contribution test in cases with a single defendant. The Court did note, however, that new situations, including those involving mass toxic tort litigation with multiple plaintiffs, may give rise to new considerations and, implicitly, new applications, of the test.

This case may impact complex negligence cases involving multiple defendants. Possible examples include product liability cases, where more than one entity may be involved in the development, testing, manufacturing, marketing and sale of an allegedly defective product, or environmental/pollution cases, where it may be alleged that aggregate acts of multiple industries over time have caused harm. In each case, application of appropriate causation principles will be dependent on the specific facts and it can be expected that further guidance in this complicated area will be provided as the trial courts attempt to apply the principles set out by the Supreme Court.

The decision can be found here.

The authors wish to thank Stephen Taylor, summer student, for his help in preparing this legal update.


1 2012 SCC 32.

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