In estate litigation, it may sometimes be necessary to obtain expert opinion evidence on a certain issue in order to assist the Court with making a determination on that issue. For example, if an estate trustee of an estate failed to invest estate funds or did so improperly, an expert report may be obtained to provide evidence on whether there were any lost opportunities as a result of the failure to invest estate funds properly. When determining whether to admit expert opinion evidence into the record, the Court will make a two-step inquiry:
- At the first step, the proponent of the evidence must establish the threshold requirements of admissibility. The Court will look to what is commonly known as the Mohan Criteria, which is a four-part test originating from v. Mohan, 1994 CanLII 80 (SCC), [1994] 2 SCR 9. The four criteria are: (a) relevance; (b) necessity in assisting the trier of fact; (c) the absence of any exclusionary rule; and (d) a properly qualified expert. Expert evidence that does not meet this criteria will be excluded. a. Relevance The evidence given by the expert must be logically relevant to the fact at issue. b. Necessity in assisting the trier of fact The expert opinion evidence must be necessary in the sense that it provides information “which is likely to be outside the experience and knowledge of a judge or jury“.[1] In other words, the subject-matter of the evidence must be such that ordinary people are unlikely to form a correct judgment about it if unassisted by a person with special knowledge. c. The absence of any exclusionary rule Even if expert evidence complies with (a), (b), and (d), it will not be admissible if it falls under a separate exclusionary rule of evidence (such as if it is not reliable or based on hearsay). d. A properly qualified expert The evidence must be given by someone who is shown to have acquired special or peculiar knowledge through study or experience in respect of the subject matter of the evidence.
- At the second step, which is a discretionary gatekeeping step, the Court balances the potential risks and benefits of admitting the evidence in order to decide whether the potential benefits justify the risks.[2] This is often known as a “cost-benefit analysis”. At this stage, the Court will weigh the potential benefits of the expert’s testimony being admitted against the risks of it being admitted, such as whether it will cause confusion, whether it will take too much time to consider, or whether it carries a prejudicial weight that outweighs its reliability.
Expert opinion evidence can be rejected by the Court and deemed inadmissible if there is a lack of independence or impartiality. In White Burgess, the Supreme Court of Canada wrote “the dominant approach in Canadian common law is to treat independence and impartiality as bearing not just on the weight but also on the admissibility of the evidence”.[3] An expert has a duty to provide fair, objective, and non-partisan evidence. Expert opinion evidence will not be automatically accepted as admissible by the Court simply because a party has taken the steps to obtain that evidence. The Court has a role to assess and analyze the expert opinion evidence to ensure that it is appropriate to consider in the specific circumstances of the case.
[1] R. v. Abbey, 1982 CanLII 25 (SCC), [1982] 2 S.C.R. 24, at page 42. [2] White Burgess Langille Inman v. Abbott and Haliburton Co., 2015 SCC 23 (CanLII), [2015] 2 SCR 182, at para. 24. [3] White Burgess, at para. 40.
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