In Hacopian-Armen Estate v. Mahmoud, 2021 ONCA 545, the Court of Appeal for Ontario considered issues of factual and legal causation in the context of medical negligence cases involving competing expert evidence.
The plaintiff, Armineh Hacopian-Armen, died on August 24, 2011, as a result of Stage IV uterine leiomyosarcoma (“uLMS”). The respondents, members of her family, brought this action against the appellant, her gynecologist. They alleged that the appellant was negligent when he examined Ms. Hacopian-Armen on May 25, 2009, in failing to conduct an endometrial biopsy, a simple in-office procedure for the detection of uterine pathologies and abnormalities. The respondents claimed that this would probably have detected her cancer at an early stage, when treatment would likely have been effective.
At trial, the trial judge found that the appellant breached the standard of care, the plaintiffs suffered damages as a result, the damage was foreseeable, and the defendant’s negligence caused the damages.
On appeal, the appellant did not challenge the trial judge’s finding that he breached the standard of care, but argued that the trial judge erred in finding that this breach of duty caused Ms. Hacopian-Armen’s death.
The Court situated the causation issues within the four required elements of a cause of action in negligence:
- that the defendant owed the plaintiff a duty of care;
- that the defendant’s conduct breached the applicable standard of care;
- that the plaintiff sustained damage; and
- that the defendant caused the damage in fact (factual causation) and in law (legal causation).
The Court found that the trial judge had outlined the proper test for legal causation:[T]he plaintiff must establish that the injuries suffered were “foreseeable or not too remote”: [I]t must be determined whether the harm is too unrelated to the wrongful conduct to hold the defendant fairly liable. The injury must have been a real risk “which could occur to the mind of a reasonable man in the position of the defendant … and which he would not brush aside as far-fetched”.
The trial judge found that, having failed to conduct an endometrial biopsy on the plaintiff at the first consultation which would have detected whether there was LMS present, it was foreseeable that the presence of uLMS, if not treated, would likely result in serious injury or death to the plaintiff, which in this case it did.
The appellant argued that the trial judge improperly blended her factual findings with her legal analysis to the effect that her assessment of causation was tainted with the knowledge of hindsight. Instead, the appellant argued, the trial judge should have asked herself whether it was foreseeable to a reasonable gynecologist that (a) the plaintiff had uLMS in May 2009; (b) an endometrial biopsy would have diagnosed the uLMS; and (c) not performing an endometrial biopsy could lead to a delayed diagnosis of uLMS.
The Court of Appeal accepted the appellant’s argument that the trial judge inappropriately blended into her foreseeability analysis her finding of fact that a biopsy performed in May 2009 would have detected the uLMS which was present. The Court stated that the foreseeability analysis should have focused on the information available to the appellant in May of 2009 when he failed to perform the biopsy.
However, the Court found that the appellant’s proposed approach to causation was too narrow and that the question was not whether the appellant was aware that the plaintiff had uLMS, specifically. What mattered was that the combination of her various risk factors indicated that a biopsy was required, and also made it reasonably foreseeable that the failure to conduct one would preclude detection of a condition that would cause her serious harm if left untreated.
The appellant was not required to foresee the presence of uLMS or the “precise concatenation of events”. Instead, legal causation required that“the harm suffered must be of a kind, type or class that was reasonably foreseeable as a result of the defendant’s negligence.”
The Court of Appeal found that, based on the evidence accepted by the trial judge, legal causation had been established.
The appellant also argued that the trial judge erred in finding factual causation – that is, whether, on a balance of probabilities, “‘but for’ the defendant’s negligence, the injury would not have occurred.”
The Court noted that many of the appellant’s arguments on this issue challenged the trial judge’s factual findings, and highlighted that the applicable standard of review was palpable and overriding error. The Court further noted that a “palpable” error may not be overriding if the impugned finding is supported by other evidence.
In order to be successful on appeal, an appellant must demonstrate that the error goes to the root of a challenged finding of fact, such that the fact cannot safely stand in the face of that error.
The appellant argued, among other things, that the trial judge misapprehended the evidence of the plaintiffs’ experts in accepting the experts’ opinions that the uLMS was probably present in May 2009, when the plaintiff visited the appellant, and that a biopsy would have detected the uLMS.
The Court held that the trial judge’s interpretation of the evidence was reasonable, consistent with the opinions given by the experts, and her interpretations were findings of fact which attracted deference on appeal. The appeal was dismissed.
This decision outlines the tests for factual and legal causation, and demonstrates their application in the context of a complex medical negligence claim involving competing experts.
In these circumstances, a judge’s assessment of an expert’s credibility will be considered a finding of fact which will be entitled to deference on appeal. Further, where there is an error of fact, if the error does not go to the root of a finding of fact, it will not be considered an overriding error warranting an appeal.
 Mustapha v. Culligan of Canada Ltd., 2008 SCC 27 at para 18
 Clements v. Clements, 2012 SCC 32 at para. 8.
 Hacopian-Armen Estate v. Mahmoud, 2021 ONCA 545 at para 69