Snell v Farrell: Causation by Inference — The Robust and Pragmatic Approach to Proving Causation in Canadian Medical Malpractice Law

Margaret Snell was seventy years old and legally blind in her right eye. She had a cataract. Surgery could restore some useful vision. It was an elective procedure (there was no urgency), and her ophthalmologist, Dr. D.H. Farrell, explained the operation and its risks before she consented. What happened during that surgery, and specifically what caused the permanent and total loss of sight in her right eye, became the central question in a case that reached the Supreme Court of Canada and produced the country’s definitive ruling on how causation must be proved in a medical malpractice claim.

Snell v Farrell, decided August 16, 1990, resolved a fundamental tension that had been dividing Canadian courts for more than a decade. That tension arose from a House of Lords decision, McGhee v National Coal Board, which had been applied by some Canadian courts to reverse the burden of proof in malpractice causation cases, relieving the plaintiff of the obligation to prove that the defendant’s negligence caused the injury. Sopinka J., writing for a unanimous Supreme Court, rejected that approach. The burden of proof of causation remains with the plaintiff. But the court also made equally clear that causation does not require scientific precision, that medical experts determine causation in terms of certainties while the law demands only a balance of probabilities, and that in cases where the facts lie particularly within the defendant’s knowledge, very little affirmative evidence from the plaintiff is needed to justify drawing an inference of causation. The result is a framework that is simultaneously principled and pragmatic, one that has governed Canadian medical malpractice causation analysis ever since.

The Clinical History

The accepted procedure for cataract removal in elderly patients in 1984, chosen to avoid the risks of general anaesthesia, was local anaesthetization followed by removal of the cataract and implantation of a prosthetic lens into the anterior chamber of the eye. Local anaesthesia was delivered by inserting a needle underneath the eyeball to inject anaesthetic into the retrobulbar muscles behind the eyeball. These muscles surround the optic nerve and control eye movement.

One complication of this injection, occurring in one to three percent of cases, is haemorrhage in the retrobulbar area. Both experts who testified at trial agreed on what should be done if retrobulbar haemorrhage occurs: the operation should not be continued. The reason is mechanical: making an incision in the cornea removes the tamponade effect created by the intact eyeball, which allows any retrobulbar haemorrhage to flow more freely. The classic signs of retrobulbar haemorrhage are redness of the eyelids where they contact the eyeball and hardness of the eye.

After injecting the anaesthetic, Dr. Farrell noticed a small discolouration, one to two centimetres in diameter, at the puncture site below the eye on the surface of the skin. At his later examination for discovery, he described this as “a very small retrobulbar bleed.” He palpitated the eye and found it was not hard. He waited thirty minutes. Then he proceeded with the surgery. The trial judge accepted Mrs. Snell’s evidence that during the operation Dr. Farrell told the assisting surgeon that he would have to hurry.

The operation itself went normally. After surgery, Mrs. Snell developed excruciating pain. That evening Dr. Farrell removed the patch on her eye and found more blood than had been present at the time of surgery; a retrobulbar bleed had obviously occurred. He found pressure on the eye, though he did not accurately measure it until a month later. Blood was present in both the anterior chamber of the eye (which cleared rapidly) and the vitreous chamber (which took approximately nine months to clear). When the vitreous chamber finally cleared, Dr. Farrell could see for the first time that the optic nerve had atrophied. Mrs. Snell had lost the sight in her right eye permanently and completely.

The Causation Problem: Why This Case Was Difficult

Optic nerve atrophy results from a loss of the optic nerve’s blood supply: the nerve, starved of oxygen, dies. One possible cause of that loss of blood supply is pressure due to retrobulbar haemorrhage. But it is not the only possible cause. Mrs. Snell suffered from controlled hypertension and controlled diabetes (both managed by diet rather than medication) and from severe glaucoma in the right eye only. Each of these conditions can, over time and in certain circumstances, cause optic nerve atrophy or compromise the blood supply to the optic nerve. A stroke in the eye (the destruction of a vessel due to an interruption of blood supply) could occur naturally, without any surgical intervention at all.

The plaintiff’s expert, Dr. Samis, examined Mrs. Snell approximately seventeen months after the operation. He found new blood vessel formation in the iris, indicating she had suffered a stroke in the back of the eye at some point. He could not identify what caused the stroke. He testified that a major cause of optic nerve atrophy is a stroke in the eye, most likely in a patient with cardiovascular disease, hypertension, or diabetes, conditions Mrs. Snell had, though in mild, diet-controlled form. He also noted that severe glaucoma in a single eye only, as Mrs. Snell had, was unusual in the absence of “an intervention of some type,” and the only intervention he was aware of was the cataract operation.

The defendant’s expert, Dr. Regan, thought the retrobulbar haemorrhage was “probably the base cause” of the atrophy, but acknowledged he could not say so with certainty. He confirmed on cross-examination that the stroke could have occurred either as a result of retrobulbar bleeding continuing and worsening, or naturally, without any traumatic interference.

Neither expert could express with certainty an opinion as to what caused the atrophy or when it occurred. The nine months of blood obscuring the optic nerve had made it impossible to observe the nerve at the critical time. Dr. Farrell himself, by continuing the operation after noticing the bleed, had made detection during that window impossible.

The Three Courts

Trial — Turnbull J. (1986): Liability Found Using the McGhee Approach

Turnbull J. found Dr. Farrell negligent in continuing with the operation after noticing the retrobulbar bleed. He accepted the evidence of both experts that the operation should have been aborted. He found that Dr. Farrell’s decision to proceed “went beyond a judgment call.” This negligence finding was not contested at any level of appeal.

On causation, Turnbull J. acknowledged that neither expert could say whether the operation had caused the injury. He found that the case fell “within an emerging branch of the law of causation” and applied the approach from McGhee v National Coal Board. He concluded that the respondent had prima facie proved that the appellant’s actions caused the injury, and that the burden having shifted to Dr. Farrell, the appellant had not satisfied it. Causation was accordingly made out.

New Brunswick Court of Appeal (1988): Affirmed

The NBCA dismissed Dr. Farrell’s appeal. The court engaged with the interpretation of McGhee that had emerged from the English Court of Appeal in Wilsher v Essex Area Health Authority. On that analysis, if it is established that conduct of a certain kind materially adds to the risk of injury, if the defendant engages in that conduct in breach of duty, and if the injury is the kind to which the conduct related, then the defendant is taken to have caused the injury even though the precise contribution made by the breach cannot be ascertained. The court found this applied to Dr. Farrell’s conduct: continuing the operation had materially added to the risk of the injury that in fact occurred.

Supreme Court of Canada — Sopinka J. (1990): Appeal Dismissed, Liability Affirmed on Different Reasoning

The SCC dismissed Dr. Farrell’s appeal. But Sopinka J. did so by rejecting the McGhee burden-reversal approach, endorsed instead a principled framework of causation by inference, and confirmed that the inference of causation was fully warranted on the evidence before the trial judge, whether or not the trial judge had intended that inference when he wrote his reasons.

The McGhee Problem and Why the SCC Rejected Burden Reversal

McGhee v National Coal Board, decided by the House of Lords in 1973, had become a touchstone for causation analysis in medical malpractice cases across the common law world. An employee had developed dermatitis from working in dusty conditions. His employer’s breach was the failure to provide washing facilities, which meant the employee rode home caked in grime after each shift. The medical evidence could not say whether the additional exposure during the ride home (the breach period) had caused the disease; the same disease might have developed even if washing facilities had been available. Five Law Lords allowed the claim, but their speeches supported two different theories.

Lord Wilberforce advocated a clean reversal of the burden of proof: if a defendant has, by breach of duty, created a risk, and injury occurs within the area of that risk, the loss should be borne by the defendant unless the defendant shows it had some other cause. Under this approach, the plaintiff need only prove the creation of risk and the occurrence of injury within that risk; causation is presumed unless the defendant disproves it.

The other speeches supported a different theory: that in circumstances where the risk of harm materially increased through the defendant’s breach, an inference of causation was justified, even without scientific proof that the breach was the cause. On this reading, McGhee established nothing new about the burden of proof; it simply permitted a robust inference from circumstantial evidence.

These two interpretations had divided Canadian courts for more than a decade. Some applied the burden reversal; others applied the inference. Sopinka J. resolved the conflict decisively: the burden reversal approach was wrong, and the inference approach was right.

The reasons were both doctrinal and practical. Doctrinally, reversing the burden of proof would compensate plaintiffs in cases where there is no substantial connection between the defendant’s conduct and the plaintiff’s injury, where the injury may very well have been due to factors unconnected to the defendant and not the fault of anyone. The comparison to Cook v Lewis, the 1951 SCC decision where two defendants negligently fired simultaneously and between them destroyed the plaintiff’s ability to prove which shot struck him, was instructive but ultimately unhelpful as a general principle: in Cook v Lewis both defendants were clearly negligent and their conduct was the indisputable cause of the injury, and the only question was which defendant specifically. It was entirely appropriate there to require the defendants to exculpate themselves. It is a different matter to impose liability on a medical defendant whose breach materially increased a risk where the injury may equally have arisen from the patient’s own pre-existing conditions and no one’s fault at all.

Practically, the experience of the United States, where liberalized rules for malpractice causation had contributed to the crisis of the 1970s, counselled restraint. Insurance premiums had increased by up to 500 percent in some states; major commercial insurers had withdrawn from the market. The Pearson Report (the Royal Commission on Civil Liability in Britain) had reached the same conclusion and declined to recommend burden reversal for similar reasons. The House of Lords had subsequently confirmed in Wilsher v Essex Area Health Authority that McGhee established no new principle of law and that the burden remained with the plaintiff throughout.

The Robust and Pragmatic Approach: What the Law Actually Requires

Sopinka J.’s positive contribution to causation law was to articulate what the traditional approach to causation actually requires when properly applied, as distinct from the rigid, science-demanding misapplication that had generated dissatisfaction and the McGhee detour in the first place.

Principle One: Causation Is a Practical Question of Fact, Not a Scientific Determination

Causation, Sopinka J. affirmed, is “essentially a practical question of fact which can best be answered by ordinary common sense rather than abstract metaphysical theory.” The law does not require scientific certainty. It does not require that experts be able to say with confidence that the defendant’s conduct was the cause. It requires only that the trier of fact be satisfied on a balance of probabilities, more likely than not, that the defendant’s conduct caused or contributed to the plaintiff’s injury.

This distinction matters enormously in medical cases. Medical experts are trained to think in terms of scientific certainties; they deal in probabilities that approach 100% before they are comfortable making causal attributions. Legal causation demands only that something be more probable than not: a 51% standard, not a 95% or 99% standard. When a medical expert says “I cannot say with certainty that X caused Y,” that admission does not mean the law’s causation standard has not been met. The expert’s standard and the law’s standard are different instruments calibrated for different purposes.

As Sopinka J. put it: “It is not therefore essential that the medical experts provide a firm opinion supporting the plaintiff’s theory of causation. Medical experts ordinarily determine causation in terms of certainties whereas a lesser standard is demanded by the law.” The trier of fact, the judge or jury, is the one sworn to make the legal determination, not the medical witnesses. Their role is to bring all the circumstances, including but not limited to the medical testimony, to bear on the legal question.

Principle Two: The Burden Remains with the Plaintiff, but Inference Can Satisfy It

The legal or ultimate burden of proof of causation always remains with the plaintiff. This is the unambiguous principle that Snell v Farrell confirmed against the McGhee burden-reversal approach. But the burden can be discharged by inference drawn from the circumstances, even in the absence of positive scientific or medical opinion evidence supporting the causal theory.

Sopinka J. clarified the language that had muddied the waters. Courts had spoken of the burden “shifting” to the defendant once the plaintiff established a prima facie case. That language was imprecise. What it means is this: evidence adduced by the plaintiff may result in an inference being drawn adverse to the defendant. Whether that inference is or is not drawn is a matter of weighing all the evidence. The defendant runs the risk of an adverse inference in the absence of evidence to the contrary, but this is a provisional or tactical risk, not a true transfer of the legal burden. The legal burden never moves.

In practical terms: the plaintiff adduces evidence pointing toward causation. The defendant then has a choice: adduce evidence to the contrary or risk that the trier of fact will draw the adverse inference. If the defendant does adduce some evidence to the contrary, the trial judge weighs that evidence against the plaintiff’s, having regard to Lord Mansfield’s principle from Blatch v Archer: “all evidence is to be weighed according to the proof which it was in the power of one side to have produced, and in the power of the other to have contradicted.”

Principle Three: The Defendant’s Superior Knowledge Reduces the Affirmative Evidence Required

In many medical malpractice cases, the facts lie particularly within the knowledge of the defendant. The physician was present during the procedure. The physician understood the clinical significance of what they observed. The physician made decisions in real time that the patient had no capacity to evaluate or even observe. Where this asymmetry exists, where the subject matter of the causal allegation lies particularly within one party’s knowledge, very little affirmative evidence on the plaintiff’s part will be sufficient to justify drawing an inference of causation in the absence of evidence to the contrary from the defendant.

This is not a reversal of the burden. It is a recognition that the amount of evidence needed to draw a permissible inference is inversely proportional to the defendant’s relative informational advantage. The greater the defendant’s knowledge of the relevant events, the easier it is for very slight plaintiff evidence to shift the risk of an adverse inference to the defendant who is best placed to rebut it.

Principle Four: A Defendant Who Destroys the Means of Detection Creates a Strong Foundation for Inference

One of the most practically important aspects of Snell v Farrell is the principle that emerges from the specific facts: when a defendant’s negligent conduct makes it impossible to detect or assess the very injury that may have been caused, that impossibility is itself a powerful foundation for drawing an inference of causation.

In Mrs. Snell’s case, Dr. Farrell’s negligent act of continuing the operation despite the retrobulbar bleed had the direct consequence of making it impossible to observe what was happening to the optic nerve during the critical nine-month period when blood obscured the chamber. The incision opened the tamponade, permitting the bleeding to flow more freely. The patching of the eye concealed the post-operative state. The blood in the vitreous chamber prevented observation of the optic nerve for nine months. It was Dr. Farrell’s breach that created these conditions of invisibility. Having made detection impossible, he was in a weak position to argue that the injury must have been caused by something other than the bleeding he facilitated.

Causation on the Facts: How the Inference Was Drawn

Applying these principles to the evidence, Sopinka J. found that an inference of causation was fully warranted on the facts, whether or not the trial judge had consciously intended such an inference when he concluded that the burden had shifted and been unsatisfied under the McGhee approach.

The critical factual elements were these. First, the trial judge had “virtually ruled out natural causes” as the source of the stroke; his finding was that retrobulbar bleeding was facilitated during the operation, and he was not inclined to the view that the atrophy resulted from natural causes. The appellant himself had confirmed in re-examination that there was “no indication” that his patient’s systemic conditions had caused the stroke, while acknowledging that the anaesthetic (the retrobulbar injection and the bleeding it caused) was part of the picture. Second, there were only two possible causes, natural and surgical, and the evidence strongly disfavoured the natural explanation. Third, Dr. Farrell’s own negligent act had made independent detection impossible: by continuing the operation, he occluded the eye with blood and made it impossible for anyone to observe what was happening to the optic nerve for nine months. Fourth, the defendant’s expert’s evidence, read carefully, pointed in the plaintiff’s direction: Dr. Regan had stated in chief that “probably the base cause is the retrobulbar hemorrhage” and had confirmed that the systemic conditions showed no “indication” of having caused the stroke.

In these circumstances, Sopinka J. was confident that had the trial judge appreciated that he did not need a positive medical opinion to draw an inference of causation, he would have drawn that inference. The court accordingly dismissed the appeal and confirmed liability.

What Snell v Farrell Establishes

Principle One: The Plaintiff Always Bears the Burden of Proving Causation

Snell v Farrell establishes without ambiguity that the burden of proving causation in a medical malpractice case rests on the plaintiff and does not shift to the defendant. This was the explicit rejection of the McGhee burden-reversal approach. A plaintiff cannot succeed by simply proving that the defendant created a risk and that injury occurred within the area of that risk. The defendant is not required to disprove causation once a risk has been established. The legal burden lies with the plaintiff throughout and is satisfied only on a balance of probabilities.

Principle Two: Scientific Precision Is Not Required — Causation Is a Practical Inference

Causation in law does not require a positive medical opinion, does not require scientific certainty, and does not require that experts be able to say with confidence that the breach was the cause. The function of the trier of fact, namely the judge, is to make a legal determination of causation based on all the evidence, including but not limited to medical testimony. The trier of fact may draw an inference of causation even when no medical expert has been willing to make a firm causal attribution, provided the circumstances justify the inference. An expert who says “I cannot say with certainty what caused this” has not answered the legal causation question. The judge, bringing ordinary common sense to the facts, may answer it differently.

Principle Three: Very Little Plaintiff Evidence Can Suffice Where Facts Lie Within the Defendant’s Knowledge

The defendant’s superior access to the relevant facts is a factor in assessing how much affirmative plaintiff evidence is needed to create the conditions for drawing an inference. Where the relevant events occurred within the defendant’s knowledge and the plaintiff had no capacity to independently assess them, the threshold for inference is lower. The defendant who fails to adduce countervailing evidence in these circumstances runs a serious risk of an adverse inference being drawn against them.

Principle Four: A Defendant Whose Breach Destroys the Means of Detection Cannot Easily Resist an Inference of Causation

Where the defendant’s own negligent conduct makes it impossible to detect or observe the injury that may have been caused, whether by obscuring the relevant evidence, by preventing independent assessment, or by creating conditions that masked the causal mechanism, that impossibility is itself probative evidence supporting an inference of causation. A defendant who creates these conditions cannot easily argue that the plaintiff has failed to prove causation that the defendant’s own conduct made undetectable.

Principle Five: Cook v Lewis Is a Special Case, Not a General Principle

Cook v Lewis, 1951 CanLII 26 (SCC), [1951] SCR 830, where both defendants negligently fired simultaneously and destroyed the plaintiff’s ability to identify which shot struck him, was appropriately decided by permitting an adverse inference against both defendants. But that case is materially different from the ordinary malpractice case. In Cook v Lewis the injury was unquestionably caused by one of the two negligent defendants. In a typical malpractice case, the injury may have arisen from natural causes that are the fault of no one. Cook v Lewis cannot be extended to support burden reversal in every case where the plaintiff faces difficulty proving causation.

Snell v Farrell in the Causation Series

Snell v Farrell is the foundational Canadian authority on the causation framework in medical malpractice law. It should be read alongside Clements v Clements, 2012 SCC 32, [2012] 2 SCR 181, which the Supreme Court decided twenty-two years later and which developed the framework further, in particular by defining the exceptional circumstances in which the material contribution to risk standard may substitute for the but-for test when but-for causation is genuinely impossible to establish. Together the two cases define the outer boundaries of causation doctrine: Snell v Farrell confirms the robust pragmatic approach to the but-for test and the use of inference; Clements v Clements identifies the narrow lane in which a different approach, material contribution to risk, is available.

In the context of the cases in this series that address causation: Wilton v Genik (1998 ONCA) illustrates causation failure even after breach is established; KS v Willox (2018 ABCA) illustrates breach established but causation failing on the evidence of what intervention was available; Murray Estate illustrates causation failure on the evidence in a general negligence context. Snell v Farrell provides the legal framework within which all of those determinations are made, the standard by which the trier of fact answers the causation question once the breach is proved.

Snell v Farrell is also relevant to every article in this series that addresses a malpractice claim dismissed at causation. The robust pragmatic approach was the applicable standard in all of them: the question was always whether, applying inference from the circumstances without requiring scientific certainty, the evidence supported a conclusion of causation on a balance of probabilities.

Quick Reference: Snell v Farrell

Case Details

• Snell v. Farrell, 1990 CanLII 70 (SCC), [1990] 2 SCR 311, 72 DLR (4th) 289 — https://canlii.ca/t/1fstw | File No. 20873 | Sopinka J. (unanimous) | August 16, 1990
• On appeal from the Court of Appeal for New Brunswick | Appeal dismissed; trial liability upheld
• Trial: 1986 CanLII 5365 (NB QB) — Turnbull J. | NBCA: 1988 CanLII 8128 (NB CA)

The Parties

• Plaintiff: Margaret Snell — age 70 at trial; legally blind in right eye; lost all sight in right eye following cataract surgery due to optic nerve atrophy from a stroke in the eye
• Defendant: Dr. D.H. Farrell — ophthalmologist; performed left cataract removal; found negligent for continuing the operation after noticing signs of retrobulbar haemorrhage

The Clinical Facts

• Procedure: cataract removal under local anaesthesia: retrobulbar injection, then incision and lens implant
• After retrobulbar injection: Dr. Farrell noticed a small discolouration (1-2 cm) at the puncture site, described on discovery as “a very small retrobulbar bleed”
• Both experts agreed: if retrobulbar haemorrhage occurs, the operation must not be continued
• Dr. Farrell palpitated the eye (not hard), waited 30 minutes, then proceeded, telling his assistant he would “have to hurry”
• Post-operatively: excruciating pain; blood in vitreous chamber obscured the optic nerve for nine months
• When chamber cleared: optic nerve had atrophied, and Mrs. Snell permanently and totally lost sight in her right eye
• Negligence not contested at any level: continuing the operation after the bleed was negligence
• Causation problem: neither expert could say with certainty whether the operation or natural causes (hypertension, diabetes, glaucoma) caused the stroke that led to the atrophy
• Additional problem: Dr. Farrell’s continuation of the operation made it impossible for anyone to observe the optic nerve during the critical nine-month period

The McGhee Question and Why It Was Rejected

• McGhee v National Coal Board [1973] 1 WLR 1 (House of Lords): dermatitis caused by working conditions; employer in breach (no washing facilities); no proof the extra exposure during the breach period caused the disease; House of Lords allowed claim
• Two interpretations of McGhee: (1) Lord Wilberforce, burden reversal: plaintiff proves risk created and injury in area of risk; (2) inference approach, common sense inference from circumstances without scientific proof
• Wilsher v Essex Area Health Authority [1988] 2 WLR 557 (House of Lords): Lord Bridge: McGhee established no new principle; affirmed that burden remains with plaintiff; endorsed “robust and pragmatic approach” to inference
• SCC in Snell v Farrell: REJECTS burden reversal; ADOPTS the robust and pragmatic inference approach
• Reason for rejection: would compensate plaintiffs where injury may be due to natural causes unconnected to the defendant; the Cook v Lewis special case (both defendants clearly negligent, means of proof destroyed) cannot be generalized

The Robust and Pragmatic Approach — Core Principles

• The legal/ultimate burden of proving causation remains with the plaintiff throughout; it never shifts to the defendant
• Causation is an essentially practical question of fact answerable by ordinary common sense, not a scientific determination requiring expert certainty
• A positive medical opinion supporting the plaintiff’s causal theory is NOT essential; inference from the circumstances suffices
• Medical experts determine causation in terms of scientific certainties; the law demands only a balance of probabilities (more than 50%); the trier of fact, not the medical expert, makes the legal determination
• Where facts lie particularly within the defendant’s knowledge, very little affirmative plaintiff evidence is needed to justify drawing an inference of causation in the absence of defendant’s contrary evidence
• A defendant who adduces no contrary evidence runs the risk of an adverse inference; this is a provisional/tactical risk, not a true shift of the legal burden
• A defendant whose breach makes it impossible to detect or observe the alleged causal mechanism provides a strong foundation for drawing an inference of causation
• If the defendant does adduce some contrary evidence, it is weighed by the trial judge according to Blatch v Archer: evidence is weighed by reference to what each party was in a position to produce and contradict

Application on the Facts

• Negligence: Dr. Farrell continued the operation despite a retrobulbar bleed; not contested
• Two possible causes of the stroke: (1) natural (systemic conditions); (2) retrobulbar haemorrhage from continuing the operation
• Trial judge “virtually ruled out natural causes”; Dr. Farrell himself confirmed no indication systemic conditions caused the stroke
• Dr. Farrell’s own expert: “probably the base cause is the retrobulbar hemorrhage”
• Dr. Farrell’s breach made detection impossible: blood in the vitreous chamber obscured the optic nerve for nine months; palpitation had failed to disclose the bleeding; the incision removed the tamponade and permitted the bleed to flow freely
• Inference of causation was fully warranted on these facts; SCC drew the inference and dismissed the appeal

Key Cases Referenced

• McGhee v National Coal Board [1973] 1 WLR 1 (HL): NOT FOLLOWED on the burden-reversal interpretation; considered for the inference interpretation
• Wilsher v Essex Area Health Authority [1988] 2 WLR 557 (HL): CONSIDERED; Lord Bridge’s “robust and pragmatic approach” endorsed
• Cook v Lewis, 1951 CanLII 26 (SCC), [1951] SCR 830: simultaneous negligent shooting; burden can shift where both defendants clearly negligent and destroyed means of proof; distinguished as a special case not applicable to ordinary malpractice causation
• Clements v Clements, 2012 SCC 32, [2012] 2 SCR 181: subsequent SCC decision defining material contribution to risk as a limited exceptional alternative to but-for causation; separate article in this series

Related Cases in This Series

• Clements v Clements, 2012 SCC 32 — the SCC’s subsequent framework for when material contribution to risk may substitute for but-for causation; companion case in this series
• Benhaim v St-Germain — adverse inference from failure to investigate; applies the Snell v Farrell inference principle; article in this series
• Wilton v Genik, 1998 ONCA — causation failure even after breach established; but-for not satisfied on the evidence; article in this series
• KS v Willox, 2018 ABCA — https://canlii.ca/t/htrbz — breach proved but causation failed on availability of intervention; article in this series
• Uribe v Tsandelis, 2021 ONCA 377 — https://canlii.ca/t/jg7mt — causation by omission; jury’s but-for reasoning in multi-defendant context; article in this series