A participant expert witness has relevant expertise and was involved in the events that underlie the litigation. Participant experts are generally permitted to provide both fact and limited opinion evidence. Occasionally, a participant expert is also a litigant.
In Westerhof v Gee Estate, the Ontario Court of Appeal addressed whether the Ontario Rules of Civil Procedure1 relating to expert witnesses also apply to participant experts. The Court noted that participant experts include "treating physicians, who form opinions based on their participation in the underlying events ... rather than because they were engaged by a party to the litigation to form an opinion."
According to Westerhof, a participant witness may give opinion evidence where:
- The opinion to be given is based on the witness’s observation of or participation in the events at issue; and
- The witness formed the opinion to be given as part of the ordinary exercise of his or her skill, knowledge, training and experience while observing or participating in such events.
Westerhof has been applied to some degree by at least the Manitoba Court of Appeal, Alberta Court of Appeal, and the Tax Court of Canada.
A litigant who has expertise and was involved in the events underlying litigation has a relevant expert opinion and is entitled to explain how and why they did what they did, which will typically require them to engage their expertise. These witnesses do not neatly fall into the White Burgess and Mohan analysis, and it is unnecessary to prove that this type of expert witness is impartial, independent, or unbiased as required by White Burgess. The Alberta Court of Appeal noted that such witnesses generally do not need to be qualified as experts under Mohan, and stated:
As parties to the litigation they are entitled to testify, and generally they will have the most direct and relevant evidence about the issues. The truth finding function of a trial requires that their evidence be received. Since they were often only involved in the underlying events because of their expertise, it makes no sense to hold that they cannot explain why they acted as they did, if they stray into their expertise. Their opinions explain why they acted as they did. Since these witnesses are available for pre-trial questioning, formal advance notice of their opinions or their evidence is not needed.
As always, the Court retains its gatekeeper function in relation to opinion evidence from participant experts.
Saskatchewan courts have not extensively commented on this and our Queen's Bench Rules are largely silent on the issue. Pre-Westerhof, this Court did comment on the distinction between "participant experts" and "litigation experts" in North Pacific Roadbuilders Ltd. v Aecom Canada Ltd. While that case may be of only limited assistance to a situation where the participant expert is also a litigant, it does clearly identify the distinction between opinions given by participant experts and those retained for the purpose of providing expert opinion evidence.
1Ontario Rules of Civil Procedure, O Reg 575/07 (the "Ontario Rules"). Similar to Rules 5-39 and 5-40 of Saskatchewan's Queen's Bench Rules, Ontario Rule 53.03 provides specific procedural requirements that must be satisfied for an expert to provide an opinion at trial with respect to a particular issue.
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