R v Swain, [1991] 1 S.C.R. 933 is a leading constitutional decision of the Supreme Court of Canada on certain rights of the mentally ill in their criminal defence. The case concerned a constitutional challenge of the common law rule permitting the Crown to adduce evidence of an accused's insanity and section 542(2) of the Criminal Code, which allowed for the indeterminate detention of an accused who is found not guilty by reason of "insanity". The Court held that both the common law rule and the Code provision were unconstitutional. As a result, the Court created a new common law rule that was constitutional, and Parliament created new laws of what to do with individuals who were found not criminally responsible by reason of a mental disorder. The parties to the case were the appellant, Swain, the respondent, the Crown, and the following interveners: the Attorney General of Canada, the Lieutenant Governor's Board of Review of Ontario, the Canadian Disability Rights Council, the Canadian Mental Health Association, and the Canadian Association for Community Living.