LEGAL PRINCIPLE: CRIMINAL LAW – Defence of Insanity – Presumption of Sanity Persists Until Rebutted by Evidence

The law presumes sanity—everyone is assumed mentally competent and responsible for their actions unless proven otherwise. This presumption reflects that most people are sane and places the burden on those claiming insanity to prove it. To rebut the presumption, the accused (or prosecution where appropriate) must adduce credible evidence of insanity: psychiatric testimony, evidence of prior mental illness, behavior demonstrating mental disorder. The presumption applies at the relevant time—criminal act, trial, sentencing. It shifts an evidential burden but doesn’t alter the prosecution’s ultimate burden of proving guilt beyond reasonable doubt. The principle ensures insanity defenses rest on actual evidence, not speculation, while recognizing that genuine mental illness negates criminal responsibility.