What are “Participant Experts”?
by Chris Wullum
In the decision of Westerhof v. Gee Estate, 2015 ONCA 55 , the Ontario Court of Appeal considered the issue of whether treating physicians could provide opinion evidence about a party’s medical condition without having to comply with the usual traditional formalities of an expert report and the Ontario Court Rule 53.03. The trial level decision, had concluded that evidence from treating physicians of diagnosis and prognosis are opinions, and that such evidence was only admissible to establish the basis of the treatment being provided and not as evidence to provide the truth of the diagnosis or prognosis.
The Court of Appeal however decided the question in the affirmative, overturning the trial court’s decision. The Ontario Court of Appeal decided that it was admissible to allow a witness with special skill, knowledge, training, or experience, who has not been engaged by or on behalf of a party to the litigation, to give opinion evidence for the truth of its contents without the requirement of complying with the Court Rules concerning experts and expert reports.
The circumstances where this might be permitted were described by the Court as follows:
- the opinion to be given is based on the witness’ 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.
In previous cases, Courts have often referred to such witnesses as “fact witnesses”, given that their evidence derives from their involvement in the facts of the case, usually as treating physicians. However, the Ontario Court preferred to use the term “participant expert” to avoid confusion as to whether their evidence relates solely to their observations of the underlying facts, or extends to their opinions formed from those observations.
In that regard, it is important to note that it is not the type of evidence that is significant, it is the manner in which the opinion was formed. In other words, the opinion must flow from the two criteria described above.
As with any opinion evidence sought to be tendered at a trial, the trial judge retains a gatekeeper function concerning its ultimate admissibility. For instance, the judge could find that the admissibility threshold is not established when weighing the overall competing considerations for admitting the evidence, such that the potential helpfulness of the evidence is not outweighed by the risks or the dangers associated with its admission. As well, the Court could consider that the opinion went beyond the scope of the opinion formed in the course of treatment or observation and therefore should be further restricted.
The usefulness of “participant experts” in personal injury litigation and in particular medical malpractice cases is significant in assisting to prove a diagnosis or prognosis without the need to engage an independent expert. Moreover, it also eliminates the necessity of complying with the formalities of the Court Rules for expert reports and notice of the opinion evidence. Therefore, this decision may be an important tool in such cases.