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Strategies for Effective Cross-Examination

Strategies for Effective Cross-Examination

By Richard Bogoroch

September 23, 2005

V. Expert Evidence: When Admissible22

Four criteria known as the “Mohan test”23 must be satisfied in order for expert opinion evidence to be admissible.

A. Necessity in assisting the trier of fact.
B. Relevance.
C. A properly qualified expert.
D. The absence of any exclusionary rule that would prohibit the admission of the opinion.

Of relevance to our discussion is the third criteria: a properly qualified expert.

Expertise is determined during the qualification phase of the examination-in-chief of the expert, and is “a modest status that is achieved when the expert possesses special knowledge and experience going beyond that of the trier of fact.”24 Although the expert may have scant experience in a particular area, this limitation will effect the weight of the evidence but not its admissibility. In this regard, R. v. Marquard25is highly important. In Marquard, doctors who had no expertise in burns were allowed to give evidence that a child’s injury was caused by a contact rather than a flame burn.26 Moreover, the “expertise” rule was not offended by allowing a plastic surgeon who was not an expert in child abuse cases to testify that the passivity of children to treatment is a characteristic common to abused children.27 Marquard altered the landscape for the reception of opinion evidence of experts who testify as to matters beyond their expertise. As Mr. Justice Griffith’s has noted.28

“The test of expertness is the skill in the field in which the expert opinion is sought. The court will not be overly concerned with whether the skill of the witness has been derived from specific studies or by practical training. That is, it does not matter whether the expertise has been acquired through training in the field, studies or by practical observation.”

22David Paciocco and Lee Stuesser, The Law of Evidence, 3 ed., Irwin Law, 2002, at pg. 161
23(1994) 2 S.C.R. 9, Paciocco and Stuesser, at p. 170
24Ibid, pg. 170
25(1993) 4 S.C.R. 223
26Paciocco and Stuesser, at p. 170
27Ibid, pg. 170
28Quoted in the Litigator’s Guide to Expert Witnesses by Mark J. Freiman and Mark L. Berenblut, (1997) Canada Law Book, at pg. 32
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Strategies for Effective Cross-Examination