Canada: Westerhoff And McCallum: More From The OCA On Expert Evidence

Last Updated: April 1 2015
Article by Christina Porretta

The Ontario Court of Appeal released its decision last week in Westerhof v. Gee Estate and McCallum v. Baker (2015 ONCA 206), which are the companion cases to Moore v. Getahun.  All three appeals were heard together.

The legal issue before the Court in Westerhof   and McCallum was whether participant experts and non-party experts could give opinion evidence without having to comply with Rule 53.03, which describes the deadlines and content requirements for expert reports.

The Court of Appeal held that the Divisional Court erred in concluding that the type of evidence – whether fact or opinion – is the key factor in determining to whom Rule 53.03 applies.

Rather, the Court of Appeal was unanimous in that participant experts and non-party experts may give opinion evidence without complying with Rule 53.03.  As a result, Rule 53.03 does not apply to the opinion evidence of a non-party expert or participant expert where he or she has formed a relevant opinion based on personal observations or examinations relating to the subject matter of the litigation for a purpose other than the litigation.


At the trial of Mr. Westerhof, the plaintiff proposed to call evidence from nine medical witnesses.  From the outset, the trial judge ruled that the medical witnesses who treated or assessed the plaintiff but did not comply with Rule 53.03 would not be entitled to give opinion evidence concerning their diagnosis or prognosis, even though they had not been retained for the purpose of the litigation. Those witnesses were also prevented from giving evidence of the history they had taken from Westerhof. The Divisional Court upheld the trial judge's conclusion.  The Court of Appeal did not agree and reversed the decision, ordering a new trial.

At the trial of Mr. McCallum, the defendant appealed that decision on the basis, inter alia, that the trial judge erred by allowing treating medical practitioners who had not complied with Rule 53.03 to give "an avalanche" of opinion evidence.  The Court of Appeal dismissed this appeal.

Principles set out by the Court of Appeal

Simmons J.A., writing on behalf of the Court of Appeal, concluded that a witness with special skill, knowledge, training or experience who has not been engaged by or on behalf of a party to the litigation may give opinion evidence for the truth of its contents without complying with Rule 53.03 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.

The Court also tried to clear the confusion that often arises from referring to these witnesses as "fact witnesses" because their evidence is derived from their observations of or involvement in the underlying facts.  Simmons J.A. preferred to refer to these witnesses as "participant experts," which takes into account that in addition to providing evidence relating to their observations of the underlying facts, they may also give opinion evidence admissible for its truth.  As with all evidence, and especially opinion evidence, the Court reiterated that it retains its gatekeeper function in relation to opinion evidence from participant experts and non-party experts.

Six factors were cited by the Court as reasons why the Divisional Court erred:

  1. The Divisional Court failed to refer to a single case under the pre-2010 jurisprudence, which support the conclusion that Rule 53.03 does not apply to opinion evidence given by participant experts. The Court reiterated its view in Moore that "the 2010 amendments to rule 53.03 did not create new duties but rather codified and reinforced ... basic common law principles."  The Court found no basis for the Divisional Court to conclude that the pre-2010 jurisprudence did not continue to apply following the 2010 amendments to the Rules relating to expert witnesses.
  2. Apart from Westerhof, no cases were brought to the Court's attention that support the view that participant experts are obliged to comply with Rule 53.03 when giving evidence concerning treatment opinions.
  3. There was nothing in Justice Osborne's Report on the Civil Justice Reform Project that indicated an intention to address participant experts or non-party experts; rather, the focus was litigation experts – expert witnesses engaged by or on behalf of a party to provide opinion evidence in relation to a proceeding.
  4. The use of the words "expert engaged by or on behalf of a party to provide [opinion] evidence in relation to a proceeding" in Rule 4.1.01 and Form 53 makes it clear that an expert must be "engaged by or on behalf of a party to provide [opinion] evidence in relation to the proceeding before the rule applies.  The Court concluded that witnesses, albeit ones with expertise, testifying to opinions formed during their involved in a matter, do not come within this description.  They are not engaged by a party to form their opinions, and they do not form their opinions for the purpose of the litigation.
  5. The Court was not persuaded that disclosure problems exist in relation to the opinions of participant experts and non-party experts requiring that they comply with Rule 53.03.  Quite often, these experts will have prepared documents summarizing their opinions about the matter contemporaneously with their involved, which can be obtained as part of the discovery process.  In addition, it is open to a party to seek disclosure of any opinions, notes or records of participant experts and non-party experts the opposing party intends to rely on at trial.
  6. Requiring participant witnesses and non-party experts to comply with Rule 53.03 can only add to the cost of the litigation, create the possibility of delay because of potential difficulties in obtaining Rule 53.03 compliant reports, and add unnecessarily to the workload of persons not expected to have to write Rule 53.03 compliant reports.

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