Legal Blog

But for

Most of us understand the concept of negligence. We first need a duty of care – from the defendant to the plaintiff. We then need a breach of the duty of care and injury to the plaintiff. However, this concept of negligence is not enough to establish liability. The injured plaintiff must also show causation (i.e. the defendant’s negligence has caused the plaintiff’s injury). Negligence without causation results in a plaintiff receiving no compensation whatever.

A number of Supreme Court of Canada cases over the last 20 years or so have grappled with the causation concept, but the latest, Clements (Litigation Guardian of) v. Clements [2012] 2 S.C.R. 181, seems to tie them together and definitively set out the tests for causation.

Accident

Husband and wife were motorcyclists. In August, they were on a trip from northern British Columbia to Kananaskis, Alberta. Husband was driving and wife was sitting behind him. The bike was overloaded by 100lb and a nail had punctured the bike’s rear tire. Husband accelerated to 120 km/hr to pass a car, the nail popped out, the tire deflated, and the bike began to wobble. Husband was unable to bring the bike under control; it crashed and wife suffered severe brain injuries. She sued husband claiming that his negligence caused her injuries.

Husband, as driver, owed a duty of care to wife. He was negligent, given that he was driving an overloaded bike at a speed that was 20 km/hr more than the speed limit. The real question was whether his negligence caused the accident. Husband’s insurer called an expert witness who testified that the probable cause of the accident was the tire puncture and deflation and that the accident would have happened without husband’s negligence.

The trial judge rejected this evidence. She decided that husband’s negligence materially contributed to the accident and that, accordingly, husband was liable for wife’s injuries. Conversely, she held that, due to the limitations of scientific reconstruction evidence, wife could not prove the accident would have happened “but for” husband’s negligence. In short, she held that husband was not liable under the “but for” test, but was liable on the material contribution test.

The trial judge got both her tests wrong. This is why.

Basic

The “but for” test is relatively simple and often easy to apply. The plaintiff must show on a balance of probabilities that “but for” the defendant’s negligent act, the injury would not have occurred (i.e. the defendant’s negligence was necessary to bring about the injury). This is a finding of fact. The “but for” causation may be demonstrated directly (e.g. he fell asleep at the wheel and hit a pedestrian) or by inference (i.e. it is not proven as a fact by ordinary logic or scientific evidence, but it can be inferred from all of the circumstances).

When “but for” causation can only be established by inference, then the defendant may lead evidence or argue that the accident would have happened regardless of the defendant’s negligence (i.e. it was inevitable).

The trial judge made her first error regarding this test. She held that because wife could not prove scientifically that the accident would not have happened but for husband’s negligence, wife did not satisfy the test. The Court noted that scientific evidence was not necessary. “A trial judge is to take a robust and pragmatic approach to determining if a plaintiff has established that the defendant’s negligence caused her loss.”

Material

Sometimes, though rarely, the “but for” test just does not work. In those circumstances, the court has to determine whether a defendant’s actions materially contributed to the risk of injury that ultimately occurred.

However, this test is limited to one set of circumstances only. There must be multiple actors, each of whom materially contributed to the risk, but it must be impossible to determine which of these actors actually caused the accident. The law will not let these defendants point the finger of blame at each other and leave the plaintiff without a remedy merely because the plaintiff is unable to determine which one of them was the cause.

As an example, take a case that we studied too many years ago. Two hunters each discharged their rifles. One of the blasts hit the defendant. Each hunter blamed the other. The plaintiff could not prove which one had shot him, but it was obviously one of them. Each was held liable.

Difference

The Court noted “‘But for’ causation and liability on the basis of material contribution to risk are two different beasts. ‘But for’ causation is a factual inquiry into what likely happened. The material contribution to risk test removes the required ‘but for’ causation and substitutes proof of material contribution to risk.”  The material contribution test is a policy driven rule allowing the plaintiff to jump the evidential gap because to do otherwise would offend basic notions of fairness and justice. In the hunting example, it would not have been fair to allow the two hunters to escape liability.

The Court stressed that the material contribution test is rarely used and went on to analyse the prior cases to demonstrate how, although mentioned, the test was never actually used in those decisions. The Court limited the test to a situation in which the plaintiff would not have been injured “but for” the defendants viewed globally, but the plaintiff was not able to prove, on a balance of probabilities, which of the defendants actually caused the injuries.

This was the trial judge’s second error. She held husband liable based on the material contribution test. However, that test could not apply. There was only one defendant. The issue could only be whether the accident would not have occurred but for husband’s negligence.

Result

The trial judge had rejected the expert’s testimony that the accident would have happened regardless of husband’s negligence. She used language that seemed to indicate that she felt that wife had established “but for” liability were it not for the judge’s misapprehension of the necessity of scientific evidence. However, she used this language in the context of her discussion of the material contribution test.

The minority (one) agreed with the majority’s analysis of causation and the “but for” test, but disagreed with the result. He felt that wife had not led any evidence regarding what would have happened if the motorcycle had been travelling at a lesser speed without any excess weight. He noted that common sense inferences cannot be pulled out of thin air at the whim of the fact finder. According, he held that the action should be dismissed and did not warrant a new trial.

The majority (8 of them) decided that the trial judge had missed the legal tests so completely that they had to send the case back for re-trial. They simply were not sure what the trial judge would have done had she applied the correct tests.