Admissibility of Expert Evidence

The Supreme Court of Canada recently commented on the standards for admissibility of expert evidence.  Although the case originated out of Nova Scotia, it is equally applicable to Ontario and should be taken into account when retaining experts. 

In White Burgess Langille Inman v. Abbott and Haliburton Co., 2015 S.C.C. 23,  shareholders started an action against the company's former auditors after a different accounting firm (Grant Thornton) identified problems with the former auditors' work.  In response to the defendant's summary judgment motion, the plaintiffs hired a forensic accountant from Grant Thornton to prepare an opinion.  The motions judge struck out the forensic accountant's affidavit on the basis that she was not an impartial witness; the Court of Appeal allowed the appeal.

The Supreme Court of Canada dismissed the appeal.

The inquiry for determining the admissibility of expert evidence is divided into two steps.  First, the proponent of the evidence must establish the threshold requirements for admissibility (found in R. v. Mohan): relevance, necessity, absence of an exclusionary rule and a properly qualified expert.  Second, the judge must exercise a gatekeeper function and balance the potential risks and benefits of admitting the evidence to determine whether the potential benefits outweigh the risks. Concerns about an expert's independence or impartiality should be considered as part of the overall weighing of the costs and benefits of admitting the evidence.

Expert witnesses have a special duty to the court to provide fair, objective and non-partisan assistance. Underlying the duty are three concepts: impartiality, independence and absence of bias.  The expert's opinion must be impartial in the sense that it reflects an objective assessment of the questions at hand.  It must be independent in that it is the product of the expert's independent judgment, uninfluenced by who has retained him or her or the outcome of the litigation.  It must be unbiased in that it does not unfairly favour one party's position over another.

A proposed expert's independence and impartiality goes to admissibility and not simply to weight, and there is a threshold admissibility requirement in relation to this duty.  Once the threshold is met, remaining concerns about the expert's compliance with his or her duty should be considered as part of the overall cost-benefit analysis the judge conducts to carry out the gatekeeping role.

In the circumstances, the evidence should not have been excluded as there was no basis to conclude the expert was not able and willing to provide the court with fair, objective and non-partisan evidence.