Glossary term
Expert Witness
An expert witness is a person qualified by a court to give opinion evidence on a topic beyond the ordinary experience of the trier of fact, owing a duty to assist the court that overrides any duty to the retaining party.
The Supreme Court of Canada confirmed the expert witness's duty to the court in White Burgess Langille Inman v. Abbott and Haliburton Co., 2015 SCC 23. An expert who cannot or will not give independent testimony is not admissible.
Admissibility is governed by the four-part Mohan test from R. v. Mohan, [1994] 2 SCR 9: necessity, relevance, qualification of the expert, and absence of an exclusionary rule.
In BC Supreme Court civil matters, expert reports must comply with Rule 11 (notice, content, and timing). Equivalent rules govern other Canadian jurisdictions.
A digital forensics expert is qualified to give opinion evidence on topics within their specialised knowledge: forensic acquisition methodology, analysis of recovered artifacts, interpretation of audit logs, and the limits of what is and is not knowable from the evidence. The expert is not qualified to opine on legal conclusions; that remains the court's role.