By Kris Bonn
Introduction
The Manitoba Court of Appeal’s recent decision in Tripp v Ross, 2025 MBCA 25, is a significant reaffirmation of the principles governing causation in medical malpractice cases, particularly where a defendant’s negligence has created uncertainty about the cause of a plaintiff’s injury or death. The Court’s reasons, delivered by Justice Pfuetzner, provide a clear roadmap for practitioners navigating the complex intersection of medical evidence, statistical probabilities, and the legal burden of proof.
Background
The case arose from the tragic circumstances surrounding Lindsey Shaun Tripp, who died of colorectal cancer in February 2022. In January 2018, Mr. Tripp underwent a colonoscopy performed by the defendant physician, who conceded that his negligent performance of a colonoscopy delayed the diagnosis of Mr. Tripp’s colon cancer by eight months. The central issues at trial were whether this delay caused Mr. Tripp’s death and, if so, the appropriate quantum of damages.
At trial, the defendant argued that earlier diagnosis would not have altered the outcome. Both parties called expert oncologists, whose evidence was largely consistent: colon cancer is slow-growing, and once metastasized, it is almost invariably fatal. The key factual issue for causation at trial was determining whether Mr. Tripp’s cancer had already metastasized to his liver by January 2018, the time of the negligent colonoscopy. If so, even if the colon tumour had been detected at that time, it would not likely have changed the outcome. The trial judge noted that Mr. Tripp had not led evidence that the liver metastasis was probably not present in January 2018.
The trial judge found that the plaintiff was unable to meet the standard of proof, which required him to show that Mr. Tripp would have had a greater than 50% chance of survival if his cancer had been diagnosed in January 2018. However, the trial judge did find that the delayed diagnosis caused pain and suffering to Mr. Tripp and awarded him damages of $75,000. The plaintiff appealed, arguing that the trial judge erred in her approach to causation and should have drawn an adverse inference against the defendant because the negligence made it more difficult to prove causation.
The Court of Appeal’s Analysis
Justice Pfuetzner, writing for a unanimous panel, dismissed the appeal. The Court’s analysis is notable for its careful engagement with the Supreme Court of Canada’s guidance in Benhaim v St-Germain, 2016 SCC 48, and its application to the facts at hand.
1. Causation Remains a Factual Determination
The Court reaffirmed that causation is a question of fact, subject to appellate review only for palpable and overriding error. The trial judge’s findings—particularly that the liver metastasis was likely present at the time of the negligent colonoscopy—were supported by both expert evidence and statistical analysis.
2. Adverse Inference of Causation: Discretionary, Not Mandatory
A central argument on appeal was that the trial judge should have drawn an adverse inference of causation against the defendant, given that the defendant’s negligence created uncertainty. The Court of Appeal, relying on Benhaim, held that the drawing of such an inference is discretionary, not mandatory. The Court noted that the trial judge’s decision not to draw an adverse inference is a question of fact and deserves deference.
3. Statistical Evidence: Use with Caution
The Court addressed the use of statistical evidence in causation analysis, echoing the Supreme Court’s warning that statistical generalizations are not determinative in particular cases. Relying on the Supreme Court’s reasoning in Benhaim, the Court held that statistical generalizations are of limited value in determining causation in individual cases because they represent “accidental groupings” and are not linked to the actual circumstances of the patient in question.
4. Robust and Pragmatic Approach
The appellant argued that the trial judge failed to adopt a robust and pragmatic approach to causation. The Court clarified that while this phrase is often invoked, it does not alter the fundamental requirement that the plaintiff bear the burden of proof.
Key Insights for Lawyers
Causation in medical malpractice remains a high bar: Plaintiffs must establish, on a balance of probabilities, that the defendant’s negligence caused the injury or death.
Adverse inferences are not automatic: Even where negligence creates evidentiary gaps, the decision to draw an adverse inference is discretionary.
Statistical evidence is a double-edged sword: While useful, statistics must be linked to the plaintiff’s specific circumstances.
The “robust and pragmatic” mantra does not shift the burden: Plaintiffs must still prove causation on a balance of probabilities. As the Court noted, while oft-repeated in the jurisprudence, there is no particular magic to this phrase.
Conclusion
Tripp v Ross is a reminder that, even in the face of admitted negligence and tragic outcomes, the law of causation in medical malpractice is exacting. The Court of Appeal’s decision underscores the importance of individualized evidence and the limits of statistical reasoning. For practitioners, the case is a valuable guide to the current state of the law and a cautionary tale about the challenges of proving causation in complex medical cases.