S.C.C. Reaffirms Primacy of “But For” Test for Causation

In an important ruling for tort litigation, the Supreme Court of Canada today allowed an appeal from a decision of the Alberta Court of Appeal which dealt with the issues of “foreseeability” and “causation”. In the course of its reasons, the Court put the brakes on what some might view as the ascendancy of the “material contribution” test of causation.

In Resurfice Corp v. Hanke, the plaintiff had been severely burned while operating an ice-resurfacing machine. Water had been mistakenly introduced into the gasoline tank of the engine. The explosion and fire resulted from vapourized gasoline escaping and being ignited by an overhead heater.

The plaintiff sued the manufacturer and distributor of the resurfacing machine. His case against them was based on the allegation that the water and gasoline tanks on the machine were situated too close together and were similar in appearance, making it easy to confuse them.

However, in the course of his evidence at trial, the plaintiff admitted that he knew the difference between the two tanks. The trial judge found that he had not, in fact, been confused.

Accordingly, at trial, the action was dismissed. The trial judge said that the plaintiff had failed to show that it had been reasonably foreseeable, that an operator of the ice-resurfacing machine would mistake one tank for the other. He also held that the plaintiff had not proved that the defendants had caused the accident.

On appeal to the Alberta Court of Appeal, a new trial was ordered. The Court of Appeal held that the trial judge had erred in both his foreseeability and his causation analyses.

The Supreme Court of Canada said that the Court of Appeal was wrong and it restored the trial judgment, dismissing the action.


The disposition of this issue turned largely on the facts. The Court of Appeal felt that the trial judge had not analyzed the evidence properly, failing to give proper weight to some parts of it. The Supreme Court disagreed, finding that the Court of Appeal had been wrong to interfere. One interesting aspect of this part of the case was that the Court of Appeal had said that the trial judge had “failed to to consider policy matters, namely the seriousness of the injury and the relative financial positions of the parties”. The Supreme Court did not mince words in rejecting such an approach:

Foreseeability depends on what a reasonable person would anticipate, not on the seriousness of the plaintiff’s injuries (as in this case) or the depth of the defendant’s pockets.


The more significant part of today’s judgment was on the issue of causation. The Court of Appeal had suggested that where there is more than one potential cause of an injury, the “material contribution” test must be used and that the trial judge had erred in failing to do so. The Supreme Court disagreed, saying that the Court of Appeal was wrong:

To accept this conclusion is to do away with the “but for” test altogether, given that there is more than one potential cause in virtually all litigated cases of negligence. If the Court of Appeal’s reasons in this regard are endorsed, the only conclusion that could be drawn is that the default test for cause-in-fact is now the material contribution test. This is inconsistent with this Court’s judgments in Snell v. Farrell, [1990] 2 S.C.R. 311, Athey v. Leonati, at para. 14, Walker Estate v. York Finch General Hospital, [2001] 1 S.C.R. 647, 2001 SCC 23, at paras. 87-88, and Blackwater v. Plint, [2005] 3 S.C.R. 3, 2005 SCC 58, at para. 78.


Arguably, some courts have been quicker, in recent decisions, to apply the “material contribution” test in circumstances where the “but for” test does not bespeak liability on the part of the defendant. The Court of Appeal’s decision in Aristorenas v. Comcare is a very recent example in which the material contribution test was discussed. There, the Court of Appeal said that “it would seem that the material contribution test is applied to 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 the causal chain.” This might be overstating the availability of the doctrine a bit, in light of today’s ruling.

The Supreme Court’s decision has made it clear that “but for” remains the primary test of causation, even in cases of multi-cause injuries. If the plaintiff cannot meet this test, he or she will lose, unless the case involves the kind of “special circumstances” that permit the material contribution test to be used. As Chief Justice McLachlin (writing for the court) said in today’s decision, generally speaking, there are two requirements that must be met in order for “material contribution” to be invoked:

First, it must be impossible for the plaintiff to prove that the defendant’s negligence caused the plaintiff’s injury using the “but for” test. The impossibility must be due to factors that are outside of the plaintiff’s control; for example, current limits of scientific knowledge. Second, it must be clear that the defendant breached a duty of care owed to the plaintiff, thereby exposing the plaintiff to an unreasonable risk of injury, and the plaintiff must have suffered that form of injury. In other words, the plaintiff’s injury must fall within the ambit of the risk created by the defendant’s breach. In those exceptional cases where these two requirements are satisfied, liability may be imposed, even though the “but for” test is not satisfied, because it would offend basic notions of fairness and justice to deny liability by applying a “but for” approach.

Today’s ruling makes it clear that the causation requirements of tort law have not been watered down and the “but for” requirement remains as strong as ever.

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