“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 case was a medical malpractice claim, where one of the defence experts testified as to the credibility of a witness of fact. The Court of Appeal held that the judge should have directed the jury as to whether this was appropriate. A miscarriage of justice was declared, and a retrial ordered.

Full article here.