Expert Evidence

Leave to appeal from the Court of Appeal decision in R. v. Abbey, 2009 ONCA 624 has been denied by the Supreme Court of Canada. As a result Abbey now stands as the governing law relating the expert evidence. 

 

Abbey significantly changes the law relating the expert evidence; the Mohan test has been reinterpreted.

 

In Abbey an expert who conducted interviews of various gang members was asked to testify as to meaning of a teardrop tattoo.  Much of the expert's opinion was based on hearsay evidence from gang members some of whom relied on television and movies for their information.

 

In the result Abbey holds that hearsay evidence, provided it is used as a basis by an approved expert, can form the basis for admissible expert testimony.

 

More generally, under Abbey expert evidence is more easily admissible with the main question being a discretionary decision by the trial judge as to whether the danger of prejudicial effect outweighs the benefit of the expert testimony.

 

Some might suggest the effect of Abbey is to eliminate the gatekeeper role of the judge dealing with expert testimony. Perhaps a better view is that expert testimony will be more easily admitted with issues as to weight being of greater importance.

 

The Court of Appeal held:

 

[76] Using these criteria, I suggest a two-step process for determining admissibility. First, the party proffering the evidence must demonstrate the existence of certain pre conditions to the admissibility of expert evidence. For example, that party must show that the proposed witness is qualified to give the relevant opinion. Second, the trial judge must decide whether expert evidence that meets the preconditions to admissibility is sufficiently beneficial to the trial process to warrant its admission despite the potential harm to the trial process that may flow from the admission of the expert evidence. ...

 

[79] The "gatekeeper" inquiry does not involve the application of bright line rules, but instead requires an exercise of judicial discretion. The trial judge must identify and weigh competing considerations to decide whether on balance those considerations favour the admissibility of the evidence. This cost-benefit analysis is case-specific and, unlike the first phase of the admissibility inquiry, often does not admit of a straightforward "yes" or "no" answer. Different trial judges, properly applying the relevant principles in the exercise of their discretion, could in some situations come to different conclusions on admissibility.