It’s time to re-think how to use the ‘but-for’ test

This article was produced in partnership with Gluckstein Lawyers

Julius Melnitzer of Canadian Business sat down with Richard Halpern, senior counsel at Gluckstein Lawyers to discuss causation in tort

A veteran member of the plaintiff’s medical negligence bar says it’s time for change in how we think about causation in tort, by clarifying the traditional ‘but-for’ test based on its ‘counterfactual’ foundation, while dismissing, once and for all, any notion that alternative tests exist in tort for finding causation.

“The traditional test for causation, the ‘but-for’ test, which asks what the outcome would have been had the wrongful act not occurred, a ‘counterfactual’ question, can be too narrow and too limiting if it continues to be invoked as a test of ‘strong necessity’ only” says Richard Halpern, senior counsel in the Toronto office of Gluckstein Personal Injury Lawyers’, whose six Ontario locations serve clients throughout Canada. “The perception that but-for is ‘unworkable’ in cases involving multiple causes is misguided.  The problem is with how we pose the causal question.”

By way of illustration, Halpern, who has detailed his views in a paper entitled Causation and the But-For Counterfactual: Vanquishing Material Contribution to Risk, published in the Advocates’ Quarterly, posits the classical case of three small fires that have combined to destroy a plaintiff’s property. Each was not strong enough on its own to cause the damage, but became strong enough when the fires merged.

“Let’s assume, however, that only the strength of two fires was required to cause the harm. If you apply the but-for test to any one of the three fires, as the causal question is commonly posed, you risk finding that none of the fires could be said to have caused the harm. But it can’t be true that none of the fires destroyed the plaintiff’s property.  Therefore, either the test is deficient, or we are asking the wrong question.  The latter is the case.”

As well, a properly formulated causal test, according to Halpern, must be one that accounts for harm arising from multiple causes even where some causes are tortious and others innocent.  He says that courts and lawyers continue to struggle with these situations, with completely inadequate guidance from our courts.

As Halpern sees it, the core difficulty with the but-for test is that its label also substitutes for its definition.   It is important to define a test that is capable of teasing out the ‘role’ that tortious conduct plays in causing harm, even where multiple causal events occur.

Before and since the Supreme Court of Canada’s 2012 decision in Clements v. Clements, however, a so-called “alternative” to the but-for test, referred to in earlier cases as a “material contribution” test and in Clements as the “material contribution to risk” test, has emerged – at least in cases where there are two or more wrongdoer defendants, of which one or more must have caused the harm, but it is impossible to identify which.   Halpern believes that case has added to our muddled understanding of causation in tort.

“The material contribution to risk test is based on the idea that it would be unfair to deprive the plaintiff of a remedy where causation can be clearly attributed to one or more defendants,” Halpern says.

According to Halpern, however, the material contribution to risk test is hopelessly flawed.

“A material contribution test is not a test of causation at all, but a policy-based rule that relieves the plaintiff of the burden of proving causation. Its application is therefore too open-ended and random and does not address the shortcomings of the traditional but-for test.  A material contribution to risk test is not a test where but-for fails because but-for, based on Clements, must be proven globally.  No substitute, therefore, is needed under the latter test.  It, too, fails to address but-for’s shortcomings.”

“The SCC said that the plaintiff still had to prove what it called a ‘global but-for’ against the named defendants.  If that is so, why do we need an alternative test for causation when causation is proven?  What happens when innocent causes are involved?”

Instead, Halpern believes, a proper, principled test takes what he calls a true “counterfactual” approach.  That is, the causal question is asked in a way that allows causation to be found where it exists.  The causal question must tease out the “role” that the wrongful conduct played in causing the harm, even if other factors were at play, whether also wrongful or innocent.  Importantly, according to Halpern, the causal test must not demand that the tortious conduct be “necessary” to bring about the harm.

“The counterfactual seeks to determine cause by hypothetically altering a fact, or facts, and asking if the harm would have been avoided. In the three small fires example, the proper question is ‘Has the plaintiff proven on a balance of probabilities that the destruction of the property was a result of any one of the fires, on its own or in combination with one of the others?”

Under this test, because any combination of two of the three fires would have caused the damage, liability would be established.  “More importantly, it allows causation to be found where it is known to exist.”

“The advantage of the proper counterfactual question is that it properly allows liability to be found where a cause is part of a group of events – a contributor to the result if not necessary to the result,” Halpern says. “The but-for test fails because of the way we have defined it in overly simplistic terms, unnecessarily making necessity the focus.”