Lewis v R, [1979] 2 S.C.R. 821 is a famous decision of the Supreme Court of Canada on the relevance of motive in a criminal trial. The Court held that motive is never an essential element of a criminal offence but can be used as evidence to prove intent.
James Lewis and Santa Tatlay were charged with the murder of Parmjeet and Gurmail Sidhu, Tatlay's daughter and her husband. The Crown alleged that Tatlay had hired Lewis to kill the victims using an electric kettle rigged with dynamite.
At trial Lewis admitted mailing the package containing the bomb, but argued that he had been fooled by Tatlay to do so. Both accused were convicted and was upheld on appeal.
Lewis appealed to the Supreme Court on grounds that the trial judge failed to instruct the jury on the issue of motive.
The issue before the Supreme Court was whether the motive or underlying reason for the crime is relevant in establishing mens rea.
Justice Dickson, writing for a unanimous Court, held that the trial judge did not err in failing to instruct the jury on the relevance of motive.
Dickson formulated several principles of "motive" or "ulterior intention":