The legal principles that are often raised at trial when the opinion of an expert is being challenged based on reliance of inaccurate facts are outlined in two leading authority from the Supreme Court of Canada. They are R. v. Abbey, 1982 CanLii 25 (SCC) and R. v. Lavallee, 1990 CanLii 95 (SCC). These cases are pursuant to the Criminal Code of Canada the 1st dealing with an insanity pleas, and the 2nd dealing with battered woman syndrome respectively.
This ties in with being mindful of drafting letters of instruction and ensuring that the facts identified are accurate.
Here are the cases and their links – for reading material:
“In R. v. Abbey, 1982 CanLII 25 (SCC) “establishes that facts relied on or assumed by an expert for the purpose of forming an opinion must be proven in evidence before the expert opinion can be given any weight. In other words, the lack of a factual foundation will cause the expert’s opinion to be given little, if any weight.”
The approach outlined in Abbey was endorsed by the SCC R. v. Lavallee, 1990 CanLII 95 (SCC): “while each of the specific facts underlying the expert’s opinion need not be proven in evidence, there must be some admissible evidence to establish the foundation of the expert’s opinion. The more the expert relies on facts not proved in evidence, the less weight is to be given to the opinion.”
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