Ontario Court of Appeal Confirms Ongoing “Gatekeeper” Function in Respect of Expert Evidence

In its recent decision in Bruff-Murphy v. Gunawardena (Bruff-Murphy), the Court of Appeal for Ontario (Court) set aside a jury award and ordered a new trial on the basis that the trial judge did not correctly apply the Supreme Court of Canada’s (SCC) test relating to the admission of expert evidence.

The Court’s decision in Bruff-Murphy provides valuable guidance as to the nature and extent of a court’s “gatekeeper” responsibility with respect to the admission of expert evidence both when the evidence is first sought to be admitted and thereafter, if prejudice emerges that was not apparent at the time of admission.


In White Burgess Langille Inman v. Abbott and Haliburton Co. (White Burgess), the SCC provided a framework for considering the admissibility of expert evidence that is challenged for impartiality or independence concerns (see our May 2015 Blakes Bulletin: SCC Rules on Impartiality and Independence of Expert Witnesses). First, a court must determine if an expert’s opinion evidence is admissible based on the four traditional “threshold” requirements set out by the SCC in R. v. Mohan (Mohan): (i) relevance; (ii) necessity in assisting the trier of fact; (iii) absence of an exclusionary rule; and (iv) the need for the expert to be properly qualified. Second, a court has a residual discretion to act as a “gatekeeper” and weigh the costs and benefits of admitting an expert’s evidence.

At the first stage of the analysis, the SCC held in White Burgess that a court must determine if an expert is “unable or unwilling to fulfill the duty of independence.” At the second stage of the analysis, a court must satisfy itself that the potential helpfulness of the evidence is not outweighed by the dangers of admitting the expert evidence.


In Bruff-Murphy, a personal injury case, the trial judge allowed a civil jury to receive expert evidence from a contested defence expert witness with respect to the damages to which the plaintiff was entitled. The trial judge did not permit the expert to testify in respect of certain sections of his report, but allowed the balance of the expert’s testimony to proceed before the jury. The jury returned a verdict awarding the plaintiff general damages but rejecting all other heads of damages claimed by the plaintiff. As the decision was a jury verdict, no reasons for judgment accompanied the award.

However, in separate reasons pertaining to a related motion in the litigation, the trial judge expressed serious concerns about the expert’s evidence, including his testimony at trial. However, the trial judge stated that he felt “restricted and compelled” to accept the witness as an expert to give opinion evidence because of the “[v]ery high threshold before a court may exclude expert testimony for bias” established by the SCC in White Burgess.


The Court allowed the plaintiff’s appeal and ordered a new trial on the issue of damages. The Court found that the trial judge erred in two respects. First, he erred by not undertaking the second step of the White Burgess analysis described above — the gatekeeper analysis — when deciding whether to admit the expert’s evidence in the first instance. Second, the trial judge erred by not exercising his discretion to exclude the expert’s testimony in whole or in part later in the trial, when further prejudice emerged during the expert’s testimony.

Regarding the trial judge’s first error, the Court stated: “The trial judge did not reference [the] second component of his discretionary gatekeeper role. To the contrary, he appears to have believed that he was obliged to qualify [the expert] once he concluded that the witness met the initial Mohan threshold.”

After conducting its own balancing exercise, the Court concluded that the potential risks of admitting the expert’s evidence far outweighed the potential benefits, as it was evident from the expert’s report that he was intent on advocating for the defence and unwilling to properly fulfil his duties to the court.

Regarding the trial judge’s second error, the Court added that the trial judge should have exercised his ongoing gatekeeper function to deal with the expert’s problematic testimony during the trial itself when it “became apparent to the trial judge during the expert’s testimony that he crossed the line from an objective witness to an advocate for the defence.” The Court stated that courts have a “residual discretion to exclude expert evidence even after admitting it, if later in the trial prejudice emerges that was not apparent at the time of admission.”


The Bruff-Murphy decision reinforces the necessity for courts to engage in both stages of the White Burgess analysis. The Court’s decision also affirms that the discretionary gatekeeping function of a judge with respect to expert evidence continues even after the White Burgess analysis is correctly applied in qualifying an individual as an expert.

While a judge’s ongoing gatekeeper role is especially important in cases such as Bruff-Murphy where there is a jury, both courts and counsel should remain mindful that expert evidence may also become disproportionately prejudicial after it has been admitted, when considered in light of the evidence as a whole.

For further information, please contact:

Ryan Morris                   416-863-2176

or any other member of our Litigation & Dispute Resolution group.

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