Legal Principles

AuthorJohn Hollander
legal principles
chapter one
Legal Principles
Admissibility and Gatekeepers
   the Canadian law of evidence deal
with admissibility issues and they have confronted many
of the main issues that face trial lawyers concerning experts.
ese advances have resolved the dispute as to whether ex-
perts who have personal knowledge of the case are less able
to provide reliable opinions than are those retained exclu-
sively to give an opinion.
In two major decisions, White Burgess Langille Inman
v Abbott and Haliburton Co and R v Mohan, the Supreme
Court of Canada established the rules of evidence with respect
to experts. ese seminal decisions lay down much-needed
guidance for trial courts and counsel. ey form the back-
bone for the cases discussed in this handbook.
To quote from Justice Cromwell in White Burgess:
[19] . . . Mohan established a basic structure for the
law relating to the admissibility of expert opinion
evidence. That structure has two main components.
1 2015 SCC 23 [White Burgess].
2 1994 CanLII 80 (SCC) [Mohan].
    
First, there are four threshold requirements that the
proponent of the evidence must establish in order
for proposed expert opinion evidence to be admis-
sible: (1) relevance; (2) necessity in assisting the trier
of fact; (3) absence of an exclusionary rule; and (4) a
properly qualif‌ied expert . . . . Mohan also underlined
the important role of trial judges in assessing wheth-
er otherwise admissible expert evidence should be
excluded because its probative value was overborne
by its prejudicial ef‌fect—a residual discretion to ex-
clude evidence based on a cost-benef‌it analysis . . . .
[20] Mohan and the jurisprudence since, however,
have not explicitly addressed how this “cost-benef‌it”
component f‌its into the overall analysis. The reasons
in Mohan engaged in a cost-benef‌it analysis with re-
spect to particular elements of the four threshold re-
quirements, but they also noted that the cost-benef‌it
analysis could be an aspect of exercising the overall
discretion to exclude evidence whose probative value
does not justify its admission in light of its poten-
tially prejudicial ef‌fects . . . . The jurisprudence since
Mohan has also focused on particular aspects of ex-
pert opinion evidence, but again without always be-
ing explicit about where additional concerns f‌it into
the analysis. The unmistakable overall trend of the
jurisprudence, however, has been to tighten the ad-
missibility requirements and to enhance the judge’s
gatekeeping role. [References omitted.]
Here, then, are the rules, as laid down by the Supreme
Court. First, there is the issue of admissibility. Regarding this
issue, there are four factors for consideration by the trial judge:

To continue reading

Request your trial

VLEX uses login cookies to provide you with a better browsing experience. If you click on 'Accept' or continue browsing this site we consider that you accept our cookie policy. ACCEPT