Case Brief Wiki


Chaulk and Morrissette, aged 15 and 16 respectively, broke into an individual's house, plundered it of valuables and then stabbed and bludgeoned him to death. Evidence was adduced at trial that the pair were psychotic and thought that they were going to rule the world - killing the victim did not matter as he was a "loser". They knew that it was contrary to the law to kill people, but they thought that they were above the law. They were convicted by a jury and an appeal was unanimously dismissed.


  1. Is the reverse onus provision of s.16(4) of the Code inconsistent with s.11(d) of the Charter?
  2. What is the meaning of "wrong" in s.16(1) of the Criminal Code?



Lamer, writing for the majority, explained that there is a presumption of criminal capacity for an adult. For a minor child, the reverse is true. For a child over 14, the presumption of incapacity is rebuttable. A claim of insanity undermines the voluntariness of either the actus reus or the mens rea. It can also provide an excuse to criminal conduct, where intention is present; the focus is on incapacity to form a mental element – a mentally disordered person does not have the capacity to distinguish between right and wrong.

Lamer holds that "wrong" means more than legally wrong or knowing the law of the land; it also means morally wrong. The test requires that the defence establish that due to the mental illness, the accused could not appreciate that his conduct: "conformed to normal and reasonable standards of society", "breaches a standard of moral conduct" and "would be condemned".

In the case at bar, Lamer finds that the individuals, due to their megalomania, may have been unable to appreciate the moral wrongness of their actions, and thus the mental disorder defence applies. As a result, a new trial is ordered.

McLachlin, in the dissent, presented an alternative argument to validate s.16 of the Code. She contends that since sanity is a pre-condition to criminal responsibility, it falls outside of the scope of the presumption of innocence, which concerns only the actus reus and mens rea.

On the meaning of the word "wrong", McLachlin disagreed with the majority. She raises the concern that the application of a moral standard might be too vague. The jury is left to speculate about whether the mental illness affected the defendant's ability to appreciate an abstract moral code. The issue is complicated further by the facts that society does not agree on standards of morality. Where an accused euthanizes someone (such as Latimer) and believes that it is right – can that person then "hide behind" a mental disorder defence to get absolved of criminal responsibility? McLachlin suggests that "wrong" should be interpreted simple as "what one ought not to do".


The "wrong" that an accused must be unable to appreciate for their condition to be deemed a mental disorder is the moral wrongness of their action.