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Standard of Care and Causation in Medical Malpractice Class Actions

By Erin Crochetière

In Levac v. James,[1] the Court of Appeal for Ontario considered an appeal regarding the standard of care and causation in a class action alleging breach of applicable Infection Prevention and Control (“IPAC”) best practices causing infection.

In the underlying class action, the plaintiffs alleged that the defendant, Dr. James, caused the plaintiffs’ infections by failing to follow appropriate IPAC practices during epidural injection procedures.

The plaintiff class was limited to those patients who developed signs or symptoms clinically compatible with bacterial meningitis, epidural abscess, or cellulitis of a bacterial origin and/or bacteremia after receiving an epidural injection administered by Dr. James.  One of the subclasses of plaintiffs was made up of patients who were found to have been infected with a rare strain of bacteria which was found to have also colonized Dr. James (“the Genetically Linked Patients”).

The Underlying Trial

At a common issues trial, the trial judge found that Dr. James breached the standard of care by not consistently employing an “aseptic technique” (an approach aimed at the complete exclusion of harmful micro-organisms) for all epidural injections he performed during the class period.

With respect to causation, the trial judge noted the following:

  • that the plaintiffs bore the burden of proving, on a balance of probabilities, that class members would not have suffered infections “but for” Dr. James’ substandard IPAC, but that “this did not require absolute scientific certainty”.[2] and
  • a trier of fact can draw factual conclusions from circumstantial evidence, so long as he or she did not infer negligence by assuming circumstantial evidence. This can include an inference of causation based on statistical evidence.[3]

The trial judge found causation with respect to the Genetically Linked Patients based on the genetic match between the bacterial strains infecting the patients and Dr. James and expert evidence regarding the lack of a viable alternative explanation for the genetic match.

With respect to the remainder of the class, the trial judge considered expert evidence that faulty IPAC and high infection rates are correlated, as well as statistical evidence that Dr. James’ patients had a 49-69 times greater risk of serious infection as compared to the accepted level risk of infection associated with epidural injections. The trial judge adopted the “risk ratio” approach outlined in some comparable case law, which states that where a breach of the standard of care more than doubles the risk of harm, causation can be presumptively established for the class (subject to proof to the contrary in individual cases).

The trial judge concluded that, while each class member will have to demonstrate their right to a claim by showing that they partook of this common risk and suffered consequences, the inference that their injury was caused by Dr. James’ actions was statistically proven, subject to any evidence which might emerge in an individual case rebutting this presumption.

The Appeal

Dr. James appealed the decision of the trial judge on a number of grounds, including that the trial judge erred in 1) finding the appellant breached the standard of care and, 2) finding the appellant’s breaches of the standard of care caused the injuries suffered by the class.

With respect to the standard of care issue, Dr. James argued that the trial judge’s finding that he breached the standard of care owed to his patients by not using an aseptic technique for all epidural injections cannot ground liability in negligence for the entire class. Dr. James argued that, in order to ground liability in negligence with respect to the entire class, the Court was required to identify a specific breach of the standard of care which applied to each class member.

The Court of Appeal held the following:

“[…]It was open to the trial judge, relying on the expert evidence, the evidence of nurses who worked with Dr. James, and Dr. James’ own evidence, to conclude that he breached the applicable standard of care by not consistently using an aseptic technique.

IPAC is akin to a systemic policy or practice that is intended to be applied consistently. The fact that there may have been some variation in individual experience does not preclude answering the question in common given the finding that an aseptic technique was always required.


Dr. James’ failure to adhere to the required IPAC standards in all cases exposed his patients to a common risk of harm. Whether this breach led to the infections is a question for the causation analysis. Direct evidence from every Class Member was not required where the plaintiff’s theory…”[4]

With respect to causation, Dr. James argued that only patient-specific evidence, which was not considered by the trial judge, was capable of leading to any conclusion that his breach of IPAC caused the infection in any given case.  

The Court of Appeal found no error in the trial judge’s finding of causation with respect to the Genetically Linked Patients.

With respect to the remaining class members, Dr. James relied on various cases advising caution in using statistical evidence to establish causation in the manner the trial judge addressed causation at the underlying trial. Here, Dr. James argued, the dangers were exacerbated by the fact that the statistical evidence was relied upon to infer causation across an entire class.

The Court of Appeal agreed with the trial judge that, while correlation is not scientific causation, scientific certainty is not required to establish legal causation.[5] The Court further noted that deference is owed to trial judges when drawing inferences of causation based on statistics, as outlined by the Supreme Court of Canada in Benhaim v. St. Germain, 2016 SCC 48 at para 78:

”Drawing an inference from a general statistic in a particular case is an inherent, and often implicit, part of the fact-finding process. A statistic alone reveals nothing about a particular case. It must be interpreted in light of the whole of the evidence. This interpretation is the role of the trial judge, and it is entitled to considerable deference on appeal…”

The Court of Appeal held that in this case, there was powerful circumstantial evidence on which to conclude that a statistical association represented a causal link on a balance of probabilities and Dr. James failed put forward any possible viable, non-negligent explanation for the outbreak as a whole.

The Court further found that the trial judge’s finding on causation included an important caveat: “absent evidence to the contrary.” This caveat demonstrated that the trial judge recognised that the ultimate determination as to whether a class member was infected because of Dr. James’ breach remained a live issue at the individual trials, and that Dr. James could put forward evidence to rebut the presumption of causation. Further, the Court noted that this approach was consistent with case law regarding causation in medical negligence cases where the defendant is in a better position than the plaintiff to determine the cause of an injury. The Court agreed with the trial judge that this did not amount to a reversing of the onus of proof.

The Court of Appeal dismissed the appeal.

Key Takeaways

A key takeaway from this decision is that in some circumstances, there does not be a singular specific act or omission constituting a breach of the standard of care which applies to each plaintiff in a class action in order for a class-wide breach of the standard of care to be found for the purposes of a class action. Rather, the court may find a class-wide breach of the standard of care in circumstances where the breach could have occurred in different ways for different plaintiffs, particularly in cases involving a systemic policy or practice that is intended to be applied consistently.

Another key takeaway is that where there is compelling statistical evidence regarding an increased risk of harm (likely requiring at the very least a two-fold increase in risk), and there is no plausible alternative non-negligent explanation, causation may be inferred. Notably, the increase in risk to Dr. James’ patients in this case was 49-69 times the typical risk associated with the procedure at issue.

Finally, the Court in this case makes clear that a finding of causation on a class-wide basis does not preclude the defendant from leading evidence to dispute a finding of causation at individual issues trials. The finding of causation at a common issues trial therefore appears to function as a prima facie finding, which can later be rebutted by evidence from an opposing party.

[1] 2023 ONCA 73.

[2] Ibid at para 21.

[3] Ibid.

[4] Ibid at paras 48-50.

[5] Ibid at para 64.