Participant Expert Witnesses

Generally expert witnesses must be neutral and they must provide a written report of their opinion well in advance of any hearing. Last year the Ontario Court of Appeal stated that these rules did not necessarily apply to “participant experts”: Westerhof v. Gee Estate, 2015 ONCA 206. For example, a health care practitioner involved in the treatment of a patient could express opinions within the practitioner’s expertise about the matter (e.g., the nature, cause and likely prognosis about the patient’s condition). Further guidance on this principle was provided in the civil case of XPG, A Partnership v Royal Bank of Canada, 2016 ONSC 3508. The issues in the case involved grain futures contracts. A participant in the events, who was employed by one of the parties, was an expert on the issues. The Court permitted the witness to express opinions about the events in issue but not to provide broader expert opinions on the larger issues in the case. The Court held that permitting wide ranging opinions on broader issues was unfair because no expert report had been provided in advance of the hearing. The Court also indicated that the lack of independence of the expert evidence could be considered when determining how much weight to put on the opinion. It is unclear to what extent the “participant expert” exceptions to disclosure apply in regulatory hearings. In order to avoid “surprise” participant expert opinions at hearings, regulators may wish to make rules of procedure to require disclosure of participant expert opinions.