R v Lavallee

Lavallee shot her common-law partner in the back of the head as he left the room, after years of physical abuse. The SCC held that expert evidence on battered woman syndrome is admissible to assist the jury in evaluating self-defence and that the imminent-attack requirement must be understood through that lens.

After years of escalating violence, including threats made earlier the same night, Lavallee shot her partner. She testified that he had said when the others left that night he would kill her. Defence called Dr. Shane to explain battered woman syndrome.

(1) Is expert evidence on battered woman syndrome admissible? (2) How should self-defence be applied where there is a history of abuse?

Yes. Acquittal restored.

Expert evidence is admissible where lay knowledge is insufficient to evaluate the conduct at issue. Battered woman syndrome explains why a woman in such a relationship may not leave and why she may reasonably perceive imminent threat in a way the lay observer would not. Self-defence must be assessed from the perspective of a reasonable person sharing the accused's circumstances and history.

Wilson J held that the Mohan-style relevance/necessity test admitted the expert evidence. The jury could not be expected to understand the cycle of violence and its psychological effects on its own. The objective standard for self-defence does not strip the accused of her circumstances.

A landmark in Canadian criminal law's recognition of gender-based violence. Substantially shaped self-defence law leading to the 2013 statutory reforms in s.34 of the Criminal Code. Cited globally in domestic-violence cases.

R v Lavallee, [1990] 1 SCR 852, 1990 CanLII 95 (SCC).

Dickson CJ, Lamer J, Wilson J, La Forest J, L'Heureux-Dubé J, Sopinka J, Gonthier J