Without Fear or Favour? Trends and Possibilities in the Canadian Approach to Expert Human Behaviour Evidence
| Date | 01 July 2006 |
| Published date | 01 July 2006 |
| DOI | 10.1350/ijep.10.4.280 |
| Subject Matter | Article |
CANADIAN APPROACH TO EXPERT HUMAN BEHAVIOUR EVIDENCE Without fear or favour?
Trends and possibilities
in the Canadian
approach to expert
human behaviour
evidence
By Emma Cunliffe*
Sessional Lecturer and PHD Candidate at the University of British
Columbia, Vancouver BC, Canada
Abstract In RvLavallee and RvMohan, the Supreme Court of Canada established
a test for the admissibility of expert evidence which is somewhat different from
that used in other common law jurisdictions. Over the course of several more
recent decisions, the court has expressed an increasingly sceptical attitude
towards expert evidence of human behaviour. Collectively, these cases have left
the state of Canadian law unclear. Canadian commentators also disagree about
how best to navigate a path between the Scylla of uncritical reliance on expert
evidence and the Charybdis of leaving discriminatory legal reasoning
undisturbed. This article describes two proposals for reforming the Canadian
approach to expert evidence and suggests that only one has the potential to
move expert evidence jurisprudence beyond its current impasse.
280 (2006) 10 E&P 280–315 E & P
* BA LLB (Hons) (Melb), LLM (UBC); email: emma.cunliffe@gmail.com. Thanks to Professor Christine
Boyle, Professor Susan B. Boyd and Professor W. Wesley Pue for insightful comments on an earlier
version of this article and to the anonymous referee and Paul Roberts for their extremely helpful
suggestions.
1. Introduction
anadian courts have struggled over the past 15 years or so with the
question of when and on what terms to admit expert human behaviour
evidence in criminal trials. The question has come squarely before the
Supreme Court of Canada on at least five occasions since 1990 and the Court has
twice1seen fit to clarify the test for admissibility that was originally spelled out in
its decision in RvMohan.2In both cases, the apparent effect of the court’s clarifi-
cation of the Mohan test was to raise the threshold of admissibility for expert
human behaviour evidence. The Canadian debate about expert opinion evidence
shares features with similar debates in England, Australia and the United States of
America. The problems and solutions that have arisen in Canada also manifest
important differences: in part because of the influence of the Canadian Charter
of Rights and Freedoms and the effect of an activist approach to judicial
decision-making on the part of the Supreme Court of Canada.
The increasingly sceptical approach that has been adopted by Canadian courts
toward expert human behaviour evidence in recent years reflects uncertainty
about when and on what terms law should venture into other fields of knowledge.
In particular, judges and commentators differ on the subjects of how best to
assess the value of expert evidence and how to guard against being misled by
experts who are partisan or insufficiently qualified. In the wake of the 1990
decision RvLavallee,3the Supreme Court of Canada and Canadian commentators
have tended to focus on the risks presented to the judicial process by expert
evidence. Experts are increasingly constructed in Canada as dangerous to the jury
and the legal process—cases where expert evidence is excluded focus on the risk of
misleading the jury with the ‘aura of infallibility’ surrounding expertise and on
the danger that the jury will abdicate its fact finding responsibilities to experts.
The result is that the purposes for which expert human behaviour evidence may
be admitted in Canadian criminal trials are now somewhat unclear.
Arguably, Canada’s jurisprudential confusion about the proper place of expert
human behaviour evidence in criminal trials is symptomatic of a perceived
tension between the need to ensure that expert evidence is sufficiently reliable to
assist the court, and the drive to counter discrimination within legal decision-
making using lessons gleaned from social science. This tension manifests itself
in the Canadian debate over the utility of adopting admissibility criteria based
on outmoded conceptions of science. To some influential commentators, most
THE INTERNATIONAL JOURNAL OF EVIDENCE & PROOF 281
CANADIAN APPROACH TO EXPERT HUMAN BEHAVIOUR EVIDENCE
C
1InRvD (D) [2000] 2 SCR 275 and again in RvJ (L-J) [2000] 2 SCR 600.
2 [1994] 2 SCR 9.
3 [1990] 1 SCR 852.
notably Alan Gold,4adopting ‘scientific method’ as the touchstone for admissi-
bility seems to offer the promise of a reliable means of distinguishing between
good and bad empirical research. To adopt this approach, however, would be to
ignore some important lessons from the philosophy and sociology of science. In
this article, I suggest that the focus on the ‘danger’ of expert witnesses and the
resultant flight to a parodied conception of scientific method risks authorising an
over-zealous and misinformed application of the judicial gatekeeping role in
relation to expert evidence. Among other dangers, this has the potential to result
in the exclusion of evidence that can counter negative myths and stereotypes
about disadvantaged groups. I conclude by suggesting that the apparent tension
between the Canadian courts’ twin goals of ensuring reliability and countering
discrimination might be more productively explored, if not necessarily resolved,
by adopting two refinements to the Mohan test. These refinements are adapted
from a proposal put forward by Boyle and MacCrimmon.5First, the purposive
approach to the admissibility of expert opinion evidence that was first advanced
by the Supreme Court in RvLavallee6encourages a rigorous attitude to expert
evidence without falling into the trap of judging one type of expertise by
standards best suited to another. Secondly, it seems equitable to pay closer
attention to the effects of excluding particular types of expert evidence from the
trial process.
Before explaining the ways in which Canadian jurisprudence differs from its
American and certain Commonwealth counterparts, I must include a note about
terminology. In this article, ‘expert human behaviour evidence,’ means expert
evidence adduced by psychiatrists, psychologists, sociologists and other ‘soft
scientists’ about human behaviour and the motivations underpinning that
behaviour. The term includes evidence that is commonly referred to in Canada as
‘social framework evidence’7—such as expert evidence that is adduced to identify
and counter stereotypes about the behaviour and decision-making patterns of
282 E & P
CANADIAN APPROACH TO EXPERT HUMAN BEHAVIOUR EVIDENCE
4 See especially Alan D. Gold, Expert Evidence in Criminal Law: The Scientific Approach (Irwin Law:
Toronto, 2003).
5 Christine Boyle and Marilyn MacCrimmon, ‘To Serve the Cause of Justice: Disciplining Fact
Determination’ (2001) Windsor Yearbook of Access to Justice 55 at 56–7.
6 Above n. 3.
7 Mosteller prefers the term ‘group character’ to describe this type of evidence, in order to distance it
from Monahan and Walker’s paradigm for social framework evidence. See Robert P. Mosteller,
‘Syndromes and Politics in Criminal Trials and Evidence Law’ (1996) 46 Duke Law Journal 461 at 462.
Two key articles by Monahan and Walker are Laurens Walker and John Monahan, ‘Social
Frameworks, A New Use of Social Science in Law’ (1987) 73 Virginia Law Review 559; and John
Monahan and Laurens Walker, ‘Social Authority: Obtaining, Evaluating and Establishing Social
Science in Law’ (1986) 134 University of Pennsylvania Law Review 477. I agree with Mosteller that the
method of admitting social framework evidence should not be limited in the ways Monahan and
Walker suggest, but have chosen to use the more usual term to avoid confusion.
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