R. v. Mohan
Encyclopedia
R. v. Mohan [1994] 2 S.C.R. 9 is a leading Supreme Court of Canada
decision on the use of experts in trial testimony.
. 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
.
Expert evidence, stated Sopinka, should be admitted based on four criteria. It must be relevant, necessary to assist the trier of fact, should not trigger any exclusionary rules, and must be given by a properly qualified expert.
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 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.
Supreme Court of Canada
The Supreme Court of Canada is the highest court of Canada and is the final court of appeals in the Canadian justice system. The court grants permission to between 40 and 75 litigants each year to appeal decisions rendered by provincial, territorial and federal appellate courts, and its decisions...
decision on the use of experts in trial testimony.
Background
Dr. Chikmaglur Mohan was a pediatrician in North Bay, OntarioNorth Bay, Ontario
North Bay is a city in Northeastern Ontario, Canada. It is the seat of Nipissing District, and takes its name from its position on the shore of Lake Nipissing.-History:...
. He was charged with sexual assault
Sexual assault
Sexual assault is an assault of a sexual nature on another person, or any sexual act committed without consent. Although sexual assaults most frequently are by a man on a woman, it may involve any combination of two or more men, women and children....
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
Voir dire
Voir dire is a phrase in law which comes from the Anglo-Norman language. In origin it refers to an oath to tell the truth , i.e., to say what is true, what is objectively accurate or subjectively honest, or both....
, 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
Character evidence
Character evidence is a term used in the law of evidence to describe any testimony or document submitted for the purpose of proving that a person acted in a particular way on a particular occasion based on the character or disposition of that person...
.
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. It must be relevant, necessary to assist the trier of fact, should not trigger any exclusionary rules, and must be given by a properly qualified expert.
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 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.