The Defence of Mental Disorder

A Divergence in the Application of R v Oommen Among Canadian Courts and the Need for Reform

  • Nicole Welsh


The law recognizes through section 16 of the Criminal Code that, in exceptional circumstances, a person may be incapable of possessing the knowledge or intent of wrongdoing necessary to ground criminal liability by reason of mental disorder. For three decades, the Supreme Court of Canada’s decision in R v Oommen has been the leading case on when the section 16 defence applies, such that an accused may be deemed not criminally responsible on account of mental disorder. This article examines a recently emerging divide in the application of section 16 and Oommen among Canadian courts that narrows the class of accuseds who may succeed in raising the defence. It will first summarize the elements of the defence and the principles enunciated by the Supreme Court of Canada in Oommen, and the historical foundations that informed the decision. This article will then analyze the shift towards a more narrow application of section 16 and Oommen, and explain the fault in this approach in light of the history and purpose of the defence. Finally, this article will propose a law reform that would protect the public, recognize the humanity of those living with mental illness, and resolve the current confusion as to what it means to possess knowledge of wrongdoing.