When is someone an expert?

Lawyers who must prove professional standards through expert witnesses tend to gravitate towards the most senior, credentialed and respected members of the profession they can retain, preferably with much experience in giving expert testimony. But what if an experienced expert witness is not available? When does a professional become qualified to testify as an expert? Must such a person be a paragon of the profession? Does the expertise of the witness relative to the panel matter?

An “expert” is simply someone who has acquired special knowledge through study or experience. That special knowledge need not come from training alone; it may come from any source, including work experience. The state of that knowledge must be measured against the “ordinary untrained person”: R. v. Marquard, [1993] 4 S.C.R. 223 at para. 35; Lindholm v. Vankouehnett, [1998] B.C.J. No. 3092 (B.C.S.C.) at para. 7. This means that someone who has special knowledge compared to an ordinary person does not lose her expert status simply because she must testify before someone who has equivalent, or more extensive, special knowledge. Any “deficiency” in expertise is a factor that should not to affect a witness’s status as an expert, but it may go to the weight of her evidence. This means, practically speaking, that a panelist of comparable or more extensive experience may decide to accept all, some or none of the evidence an expert “colleague” based in part on her own professional knowledge.

While lawyers may tend to put forward experts who are as “heavy-weight” as possible, a professional need not be more specialized than an average or ordinary member of her profession. See R. v. N.O., 2009 ABCA 75 at para. 24. Provided the witness as the requisite knowledge to be an expert on the matters at issue, she need not be more specialized than anyone else in the profession.

Michael Ng