In Clements v. Clements 2012 SCC 32 (“Clements“), the Supreme Court of Canada (“SCC” or the “Court”) dealt with the issue of causation in negligence actions. More specifically, the Court set out the criteria for determining when the material contribution test may be substituted for the usual “but for” test of causation.
The Clements litigation involved a personal injury claim. On August 7th, 2004, Mr. and Mrs. Clements were riding a motor bike from Prince George, B.C. to Kananaskis, Alberta, to visit their daughter. Mr. Clements was driving the bike, with Mrs. Clements riding behind him in the passenger seat. The weather was wet and the bike was about 100 pounds overloaded. Unbeknownst to Mr. Clements, a nail had punctured the bike’s rear tire (Clements, para 1).
Mr. Clements accelerated, in a 100km/h zone, to at least 120km/h in an attempt to pass a car. However, as Mr. Clements passed the centre line, the nail fell out, deflating the rear tire, which caused the bike to wobble and crash. Mrs. Clements was thrown off the bike, and suffered a severe traumatic brain injury (Clements, para 1).
Mrs. Clements then sued Mr. Clements for negligence. Mr. Clements’ negligence was not disputed. The only issue was whether his negligence caused the injury to Mrs. Clements.
At trial, Mr. Clements argued that the likely cause of the accident was the puncture and subsequent deflation of the rear tire, and that the accident would have occurred even in the absence of negligence (Clements, para 2).
The trial judge found that Mr. Clements’ negligence did contribute to Mrs. Clements’ injury; however, due to limitations of the scientific reconstruction evidence, the plaintiff was unable to prove “but for” causation. Due to this impossibility, the trial judge dispensed with the “but for” test, instead applying the material contribution test. On this basis, Mr. Clements was found liable (Clements, para 3).
On appeal, the B.C. Court of Appeal set aside the trial judgment because “but for” causation had not been proven, and the material contribution test did not apply (Clements, para 4).
In the SCC, McLachlin C.J. defined the “but for” and material contribution tests, reviewed the relevant caselaw on the development of the material contribution test, and set out the circumstances in which the material contribution test may be substituted for the “but for” test of causation.
The “but for” test of causation in negligence requires the plaintiff to show “on a balance of probabilities that ‘but for’ the defendant’s negligent act, the injury would not have occurred. Inherent in the phrase ‘but for’ is the requirement that the defendant’s negligence was necessary to bring about the injury…” (Clements, para 8).
In contrast, the material contribution test asks whether or not the defendant’s negligence materially contributed to the risk that the personal injury would occur (Clements, paras 14-15).
There have been multiple cases dealing, either implicitly or explicitly, with the relationship between the two tests. Among these cases are: Cook v. Lewis,  S.C.R. 830 (“Cook“), Snell v. Farrell,  2 S.C.R. 311 (“Snell“), Athey v. Leonati,  3 S.C.R. 458 (“Athey“), Walker Estate v. York Finch General Hospital, 2001 SCC 23 (“Walker Estate“), and Resurfice Corp v. Hanke, 2007 SCC 7 (“Resurfice“).
In Cook, three men were out hunting when two of them fired their guns, hitting a fourth hunter with a single shot. Because each shooter could point to the other as the possible cause of the injury, it was impossible to prove “but for” causation against either of them (Clements, para 18).
In finding both defendants liable, the Court relaxed the usual “but for” test on the basis of fairness. Even though it could not be determined which defendant actually caused the injury, it was clear that both of them had breached their duty of care to the plaintiff, subjecting him to an unreasonable risk of injury that in fact materialized (Clements, para 19). To deny recovery in such circumstances would not have met the negligence law goals of compensation, fairness and deterrence, in a manner consistent with corrective justice (Clements, para 19).
In Snell, the plaintiff suffered, in the course of cataract surgery, bleeding that, for nine months, obscured the fact that the plaintiff’s optic nerve had atrophied, causing loss of sight in one eye. It was unclear what caused the atrophy or when it had occurred.
The SCC affirmed recovery, but did so on the basis of a robust and common sense application of the “but for” test. However, Sopinka J. suggested that, had it been necessary and appropriate, a material contribution test might have been applicable: “If I were convinced that defendants who have a substantial connection to the injury were escaping liability because plaintiffs cannot prove causation under currently applied principles, I would not hesitate to adopt one of these alternatives” (Clements, para 20).
In Athey, a plaintiff who suffered from pre-existing back problems got into two car accidents, suffering a herniated disc. He sued the drivers of the other motor vehicles in negligence.
The SCC found the defendants partially liable on the application of a robust and common sense application of the “but for” test; however, in this case, the causation requirement was satisfied by a finding that the defendants’ negligence was a “material contribution” sufficient to meet the “but for” test (Clements, para 23).
Major J. emphasized that the “but for” test permits an “inference of ‘but for’ causation from evidence that the defendant’s conduct was a significant factor in the injury” (Clements, para 23).
In Walker Estate, the plaintiff contracted HIV from tainted blood. Her estate sued the supplier for negligence in failing to prevent blood donations from those with a high risk of HIV. The suppliers argued that “but for” causation was not established because any attempt to screen out high risk donors could not prevent donations from those either unaware or unconcerned about their high risk status (Clements, para 24).
In finding the supplier liable, the Court (and more specifically, Major J.) alluded to situations, often involving multiple independent causes capable of causing injury, in which the “but for” test would be inadequate. Indeed, in obiter, Major J. set out that, in an appropriate case, it might be possible to apply the material contribution test in substitution for the “but for” test “where the ordinary principles of causation are inadequate to the task and result in unfairness and inconsistency with the underlying principles of negligence” (Clements, para 25).
In Resurfice, the plaintiff ice-maker suffered a personal injury (a burn) when he accidentally caused a fire by pouring water into the gas tank of the ice-making machine. He sued the manufacturer and distributor of the machine, alleging negligence in not making clear the distinction between the water and gas tanks (Clements, para 26).
The SCC decided that “but for” causation was not established, and that the material contribution test was inapplicable; however, the Court affirmed that in special circumstances, the material contribution test should replace the “but for” test. Such replacement would occur where it is “‘impossible’ for the plaintiff to prove causation on the ‘but for’ test, and where it is clear that the defendant breached his duty of care in a way that exposed the plaintiff to an unreasonable risk of injury” (Clements, para 27).
Thus, prior to Clements, the SCC, despite never in fact applying the material contribution test, has accepted that such a test might be appropriate in special circumstances… and it is in Clements that those circumstances are finally defined.
In Clements, the Court set out the criteria for determining when the material contribution of risk test may be substituted for the usual “but for” test:
“Exceptionally, a plaintiff may succeed by showing that the defendant’s conduct materially contributed to risk of the plaintiff’s injury, where (a) the plaintiff has established that her loss would not have occurred “but for” the negligence of two or more tortfeasors, each possibly in fact responsible for the loss; and (b) the plaintiff, through no fault of her own, is unable to show that any one of the possible tortfeasors in fact was the necessary or “but for” cause of the injury, defeating a finding of causation on a balance of probabilities against anyone” (Clements, para 46).
Ultimately, the SCC allowed the appeal and ordered a new trial (Clements, para 54), having found that the trial judge made two errors: first, the trial judge wrongly insisted on scientific reconstruction evidence as a necessary condition of finding “but for” causation; and second, the trial judge wrongly applied the material contribution test. The application of the material contribution test was faulty because “the special conditions that permit resort to a material contribution approach were not present in this case” (Clements, para 50).
Continue reading: Causation in Negligence (Part 2)