To Be or Not to Be a (Truly Qualified) Expert Witness

The practical definition of an expert witness is someone who wears a suit and a tie, carries a briefcase, and comes from over 300 kilometres away. When I was a trial judge, I found that there were supposed to be experts on every topic under the sun (and sometimes even within the shadows of the dark side of the moon). Two questions come to mind: (1) How many of these proposed experts were helpful, let alone necessary?; and (2) Was the briefcase just an expensive lunchbox?

While many trials might benefit from expert testimony, it is interesting to look at how many of these proffered experts were in fact truly qualified to testify. Allow me to expand on some of the pitfalls and provide some insight as to what is required in order that a trial proceed in a fair and efficient manner to reach a just result.

There have been some refinements to the test since Sopinka J.'s advice in R. v. Mohan, [1994] 2 S.C.R. 9. However, the summary of that case succinctly frames the issues:

Admission of expert evidence depends on the application of the following criteria: (a) relevance; (b) necessity in assisting the trier of fact; (c) the absence of any exclusionary rule; and (d) a properly qualified expert. Relevance is a threshold to be decided by the judge as a question of law. Logically relevant evidence may be excluded if its probative value is overborne by its prejudicial effect, if the time required is not commensurate with its value or if it can influence the trier of fact out of proportion to its reliability. The reliability versus effect factor has special significance in assessing the admissibility of expert evidence. Expert evidence should not be admitted where there is a danger that it will be misused or will distort the fact-finding process, or will confuse the jury.

Expert evidence, to be necessary, must likely be outside the experience and knowledge of a judge or jury and must be assessed in light of its potential to distort the fact-finding process. Necessity should not be judged by too strict a standard. The possibility the evidence will overwhelm the jury and distract them from their task can often be offset by proper instructions. Experts, however, must not be permitted to usurp the functions of the trier of fact causing a trial to degenerate to a contest of experts.

Expert evidence can be excluded if it falls afoul of an exclusionary rule of evidence separate and apart from the opinion rule itself. The evidence must be given by a witness who has shown to have acquired special or peculiar knowledge through study or experience in respect of the matters on which he or she undertakes to testify.

In summary, expert evidence which advances a novel scientific theory or technique is subjected to special scrutiny to determine whether it meets a basic threshold of reliability and whether it is essential in the sense that the trier of fact will be unable to come to a satisfactory conclusion without the assistance of the expert. The closer the evidence approaches an opinion on an ultimate issue, the stricter the application of this principle.

Sopinka J. referred to R. v. Melaragni (1992), 73 C.C.C. (3d) 348 (Ont. Gen. Div.) in which Moldaver J. applied a threshold test of reliability as to what he described as "a new scientific technique or body of scientific knowledge" (namely, "What degree of reliability has the proposed scientific technique or body of knowledge achieved?") along with two other factors to be considered in such circumstances: (1) Is the evidence likely to assist the fact-finder (jury or judge) in its fact-finding mission, or is it likely to confuse and confound?; and (2) Is the fact-finder likely to be overwhelmed by the 'mystic' infallibility of the evidence, or will the fact-finder be able to keep an open mind and objectively assess the worth of the evidence?

Binnie J. also noted in R. v. J.-L.J., [2000] S.C.R. 600 at p. 615 that the Canadian courts were open to novel science (as mentioned in Mohan), but subject to the "reliable foundation"...