933 is a leading constitutional decision of the Supreme Court of Canada on certain rights of the mentally ill in their criminal defence.

Swain testified that at the time of the incident, he believed that his wife and children were being attacked by devils, and that he had to protect them.

On November 1, 1983, Swain was transferred from jail to a mental health centre, where he was observed to be acting in a bizarre manner.

As a result of the court's finding, the Criminal Code at the time required that the person be held in custody until the Lieutenant Governor of the Province (i.e. the executive branch of the provincial government) decides to release them.

Defence counsel challenged the constitutionality of that provision, on the basis that it violated the Canadian Charter of Rights and Freedoms.

On June 10, 1985, the trial judge found that the provisions were constitutional, and ordered that Swain be detained until the Lieutenant Governor's wishes were known.

On June 12, 1985, the Lieutenant Governor issued a warrant further detaining Swain to be held in safe custody in a mental health hospital for assessment, and to report to the Advisory Review Board in 30 days.

The Lieutenant Governor issued a warrant for Swain to be held in custody with the conditions recommended by the Board.

For example, if an accused person puts their mental health at issue without going so far as to claim the defence of insanity, the Crown is entitled to "complete the picture".

In her concurring judgment, Wilson J. reached a similar reasoning with the majority, and agreed with the new common law rule.

In her dissenting judgement, L'Heureux-Dubé J. found that the old common law rule did not infringe sections 7 or 15 of the Charter, and in fact was reflective of the principles of fundamental justice.

Since the Criminal Code is a federal statute, an issue was whether the provision requiring the automatic detention by a person found not guilty by reason of insanity - until released by the Lieutenant Governor - was outside the federal government's authority to legislate, or whether it fell within provincial jurisdiction over health matters.

Since the detention is automatic with no standards or criteria that can be applied, the majority found that the law was arbitrarily detaining individuals, and violated section nine of the Canadian Charter of Rights and Freedoms.

The majority felt that minimally intrusiveness required that a person be held no longer than necessary to determine their mental state.

While normally a new trial should be ordered, the specific circumstances in this case did not warrant it: Swain had been acquitted (by reason of insanity) and had been absolutely discharged.

The insanity defence was replaced with being found not criminally responsible by reason of a mental disorder".

The new legislation requires that the least restrictive or onerous disposition be imposed, bearing in mind public safety, the mental condition of the accused, and the goal of reintegration into society.

The role of the Lieutenant Governor in these decisions was abolished, and their decision-making duties were transferred to the Review Boards.