Expert Evidence: A Refresher From The Court Of Appeal On The Key Roles Of The Judge, Expert And Counsel

• Published date: 26 May 2021
• Subject Matter: Litigation, Mediation & Arbitration, Trials & Appeals & Compensation
• Law Firm: WeirFoulds LLP
• Author: Mr John Buhlman

The Ontario Court of Appeal in Parliament v. Conley, 2021 ONCA 261 has provided a refresher for judges, experts and counsel on the roles each plays when dealing with expert evidence:

1. Judges must exercise their gatekeeping role throughout the testimony of expert witnesses;

2. Experts must stick to the area of his or her expertise and not become advocates; and

3. Counsel are to properly instruct experts and object to inadmissible expert evidence.

The Facts

Twenty-seven experts testified during this lengthy jury trial involving allegations of medical malpractice. The jury found the defendant medical doctors had met the standard of care and the judge dismissed the action. The evidence of one defence expert on the standard of care was found to be problematic; as a result, the Court of Appeal allowed the appeal, set aside the trial judgment and ordered a new trial.

One of the key issues at trial was the credibility and reliability of the plaintiff's mother and the defendant doctors (para. 17). There was a factual dispute about what the defendant doctors had said to the plaintiff's mother on the various occasions the defendants saw the plaintiff and whether the plaintiff's mother followed the instructions given by the doctors. The resolution of this factual dispute was central to the issue of the standard of care.

The expert whose evidence was problematic, Dr. Bruce, testified on behalf of the defendants about the standard of care. Dr. Bruce, a medical doctor, ignored the plaintiff's mother's evidence from her examination for discovery when he prepared his report because he did not think her recollection was accurate. He also expressed his opinion that the plaintiff's mother's memory was 'probably mistaken' (para. 53). Consequently, he chose to accept the defendants' evidence over the plaintiff's mother's evidence when giving his opinion on whether the defendants had met the standard of care.

The plaintiff's trial counsel did not object to Dr. Bruce's opinion on the credibility and reliability of the witnesses during the trial and the judge permitted the expert to testify on this point. In her instructions to the jury, the trial judge commented on the expert evidence and the plaintiff's trial counsel made comments about this expert evidence in closing; however, the Court of Appeal found that that was not sufficient to cure the problems with the expert evidence (paras. 53 and 54).

Judges are Gatekeepers

The Court of Appeal reminds us of the risk that the trier...