In last week’s blog, we reviewed the general rule as to the non-admissibility of opinion evidence and the exception for expert evidence. We also examined the two-stage test for the admissibility of any expert testimony and the common law duty of an expert to the adjudicative body before which they propose to testify.
In this blog, we will examine the duties imposed on expert witnesses by the Ontario Rules of Civil Procedure (Rules). We will also examine the admissibility of expert evidence from professionals who were not retained specifically for their expert knowledge, but rather those who came to form their opinion in the course of treating a party to the litigation, or other past involvement with the matter at hand.
Statutory Duty of Retained Experts
The Rules were amended in 2010 to add to the duty of an expert “engaged by or on behalf of a party” to provide opinion evidence “in relation to a proceeding” that is fair, neutral and non-partisan and within the expert’s area of expertise (Rule 4.1.01). The amendments (Rule 53.03(2.1)), also specified certain information relating to an expert’s opinion and expertise that must be included in an expert’s report and required that the expert sign an acknowledgement of his or her duty, which identifies the party by or on behalf of whom the expert was engaged (Form 53). Before 2010, the Rules called only for a signature, and address, the expert’s qualifications and the substance of the proposed testimony.
Not all experts who may be called to testify were retained in this way. Any of the treating health care professionals or others engaged in one of the parties’ past medical history may be called. As they were not retained to provide expert evidence but came to their knowledge through prior treatment or involvement, they do not have to comply with Rule 4.1.01 or Form 53.
The ONCA, in Westerhof v. Gee Estate, held 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.
Similarly, I conclude that Rule 53.03 does not apply to the opinion evidence of a non-party expert where the non-party expert 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.
However, it must be remembered that the SCC in White Burgess held that an expert’s lack of impartiality or bias and their independence all go to the admissibility of their evidence, as well as to the weight it ought to be given if admitted. As with all evidence, and especially all opinion evidence, the court retains its gatekeeper function. In exercising that function, a court could, if the evidence did not meet the test for admissibility, exclude all or part of the opinion evidence of a participant expert or non-party expert or rule that all or part of such evidence is not admissible for the truth of its contents.
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