In a recent decision, the Court of Appeal revisited the issue of admissibility of expert evidence, and emphasized the importance of an expert witness being independent, rather than acting as a “hired gun”.

What Happened?

The decision involved a car accident. One of the drivers involved claimed that she had suffered significant physical and mental injuries in the accident, which had been caused by the other driver (who had admitted liability). A lengthy trial followed to determine the injured driver’s damages. She was ultimately awarded more than $23,000 in general damages. The other driver appealed.

The Court of Appeal

The Court of Appeal overturned the damages award, stating that a new trial was necessary because the defence had “proferred the evidence of a wholly unsuitable expert witness”.

In support of their respective positions, each party had called a number of expert witnesses.

The injured driver relied on a number of physicians who had either treated or examined her following the accident. The consensus among them had been that she had suffered “in the manner complained of” and that the cause of her injuries had been the motor vehicle accident.

The liable driver called two medical experts who had conducted independent medical examinations. The second of these two witnesses was a psychiatrist who was of the opinion that the injured driver had not developed any psychiatric disorders or limitations from the accident.

The Court of Appeal found that, among other things, the methodology the psychiatrist had used, and the tone of his expert report were prejudicial. The Court of Appeal believed that there was a real risk of unfairness in the fact that the psychiatrist had engaged in a hunt for discrepancies between what the injured driver had said in a short interview and what her years of medical records revealed. Any inconsistencies that had been revealed should have been presented to the injured driver and she should have had an opportunity to explain the discrepancies.

The Court of Appeal went on to note that the psychiatrist had also gone “out of his way” in his expert report to make points that were intended to damage the injured driver’s case, including stating that she had misled several physicians, and speculating that one of the injured drivers’ therapists had been improperly holding herself out as a qualified psychologist.

The Court of Appeal noted that:

…in his report [the expert] goes beyond a mere lack of independence and appears to have adopted the role of advocate for the defence. Given the paucity of psychiatric analysis in the report versus the high degree of potential prejudice in wrongly swaying the jury, a cost-benefit analysis would have invariably lead to the conclusion that [the expert] should have been excluded from testifying.

Admissibility of Expert Evidence

The Court of Appeal emphasized the judge’s role as an ongoing gatekeeper, drawing attention to the test that a court should always carry out in determining admissibility of expert evidence.

The Supreme Court of Canada had earlier established the threshold needed to be met in order to exclude expert testimony for bias. The first step of such an analysis requires a court to consider the four “traditional” requirements of admissibility of evidence as established in R.v. Mohan:

  • Relevance;
  • Necessity in assisting the trier of fact;
  • Absence of an exclusionary rule;
  • Need for the expert to be properly qualified.

This is followed by a “discretionary gatekeeping step” in which the judge must balance the potential risks and benefits of admitting the evidence to decide whether the potential benefits justify the risks.  Using this cost-benefit analysis, the court must determine whether the expert evidence should be admitted because its probative value outweighs its prejudicial effect.

In this case, the Court of Appeal noted that the original trial judge had correctly turned his mind to the Mohan criteria, but had erred by failing to weigh the prejudicial effect of the expert’s evidence against its probative value. This discretionary role of a judge is ongoing and one that continues throughout a trial.

The Court of Appeal remarked:

Given this ongoing gatekeeper discretion, the question remains of what, as a practical matter, the trial judge could or should have done in this case. His first option would have been to advise counsel that he was going to give either a mid-trial or final instruction that [the psychiatrist’s] testimony would be excluded in whole or in part from the evidence. Had he taken that route, he would have received submissions from counsel in the absence of the jury and proceeded as he saw fit. Alternately, he could have asked for submissions from counsel on a mistrial, again in the absence of the jury, and ruled accordingly. In the event that he had to interrupt [the psychiatrist’s] testimony mid-trial, he would have had to consider carefully how best to minimize the potential prejudicial effect of the interruption from the respondent’s perspective.

Lessons Learned

The largest takeaway from this case is best summarized by the Court of Appeal itself when it stated:

The law regarding expert witnesses has evolved considerably over the last 20 years. Gone are the days when an expert served as a hired gun or advocate for the party that retained her. Today, expert witnesses are required to be independent, and their function is to provide the trier of fact with expert opinion evidence that is fair, objective and non-partisan. 

At Wise Health Law we have significant experience and expertise assisting health professionals in the civil and regulatory contexts, including advising health professionals about participating in trials as expert witnesses. We are highly knowledgeable and passionate about what we do. Contact us online, or at 416-915-4234 for a consultation.

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