It's interesting therefore to see the Canadian Supreme Court response to some of these problems. They had to consider whether the allegedly provocative act -- a woman's sexual involvement with another man after the couple had separated -- was sufficient to form a foundation for a provocation defence. It wasn't.
http://scc.lexum.umontreal.ca/en/2010/2010scc58/2010scc58.html
An excerpt:
[18] The common law defence of provocation was adopted and codified in the Canadian Criminal Code from its inception in 1892. The wording of s. 232 remains substantially unaltered. The same cannot be said of the social context in which it is embedded. The continued appropriateness of the defence has been a source of controversy, both in Canada and abroad. Some commentators and reviewing bodies have recommended that the defence be abandoned altogether, leaving provocation, when relevant, as a factor to be considered in sentencing. For a discussion of such reform proposals in Canada and elsewhere, see D. E. Ives, “Provocation, Excessive Force in Self-Defence and Diminished Responsibility”, in Law Commission of Great Britain, Partial Defences to Murder: Overseas Studies, Consultation Paper 173 (App. B) (2003), 73, at pp. 78-81; Australia, Victorian Law Reform Commission, Defences to Homicide: Final Report (2004); New Zealand Law Commission, The Partial Defence of Provocation, Report 98 (2007).
[19] Parliament has not chosen this course and the defence continues to exist in Canada. This does not mean, however, that the defence in its present articulation should not continue to evolve to reflect contemporary social norms, and in particular, Charter values. Just as at common law the notion of an “insult ... sufficient to deprive an ordinary person of the power of self-control”, now codified under s. 232, is not frozen in time. By incorporating this objective element, the defence of provocation is necessarily informed by contemporary social norms and values. These include society’s changed views regarding the nature of marital relationships and the present reality that a high percentage of them end in separation.
