Citations [1994] 2 SCR 9 | Unanimous reasons by Sopinka J. | |
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Full case name Her Majesty The Queen v Chikmaglur Mohan Ruling appeal was allowed and the evidence was excluded. People also search for R v Marquard, R v Handy, R v Lavallee | ||
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R v Mohan 1994 CanLII 80, [1994] 2 SCR 9 is a leading Supreme Court of Canada decision on the use of experts in trial testimony.
Contents
Background
Dr. Chikmaglur Mohan was a pediatrician in North Bay, Ontario. He was charged with sexual assault of four teenaged patients. During his trial, the defence tried to put Dr. Hill, a psychiatrist, on the stand as an expert on sexual assault. Hill was intended to testify that the culprit of the offence must have possessed several abnormal characteristics of which Mohan did not have. In a voir dire, Hill testified that the culprit of the first three assaults was likely a pedophile, while the fourth would have been by a sexual psychopath. This evidence was held to be inadmissible by the judge. Mohan was eventually convicted at trial but was overturned on appeal.
The issue before the Supreme Court was whether Hill's testimony could be admitted as an expert witness, and whether the testimony would violate the rule against character evidence.
Opinion of the Court
Justice Sopinka, for a unanimous Court, allowed the appeal and held that the evidence should be excluded.
Expert evidence, stated Sopinka, should be admitted based on four criteria:
Relevance is a question of law and so is determined by the judge. Where it approaches the "ultimate issue" of the trial the standard for inclusion must be stricter. To be considered necessary the expert evidence must likely be outside the experience of a judge and jury. In that regard, Sopinka stated:
In total, the expert evidence should be included where the probative value of the evidence outweighs any prejudicial effect it may cause.
In the current case, Sopinka found that there was insufficient evidence to suggest that there was any clear standard for determining the profile of a paedophine or psychopath. Thus, the expert evidence was not considered reliable. Furthermore, the expert's evidence was not sufficiently relevant to be of any help.
Impact
The criteria set out in Mohan did not include a stand-alone requirement for experts to have independence and impartiality, but many of the lower courts have attempted to infer it. In 2013, the Nova Scotia Court of Appeal held that that is not required. In affirming that ruling in 2015, the Supreme Court of Canada disagreed with the Nova Scotia Court of Appeal and held that the expert’s duty to the court creates a threshold requirement for the admissibility of the expert’s evidence, in which the determining factor is "whether the expert’s opinion would not change regardless of which party retained him or her."