Mistake of Fact / Error Facti /

Mistake of Fact: The Good-Faith Error That Excuses

Criminal law punishes voluntary, knowing wrongdoing — not honest mistakes. The mistake of fact defence recognises that a person who acts in genuine good faith on a false belief about facts cannot be said to have the guilty mind (mens rea) necessary for criminal liability. They did not intend to do wrong; they intended to do right based on what they (falsely but honestly) believed to be true.

Good Faith: Section 2(12) BNS

The defence of mistake of fact requires 'good faith' — which Section 2(12) BNS defines as acting with 'due care and attention.' This is not a subjective standard alone: a person who acts carelessly or without reasonable inquiry cannot claim good faith. The test is whether a reasonable, diligent person in the same circumstances would have shared the mistaken belief. A police officer who arrests someone as a fugitive without making any inquiry into their identity is not acting in good faith merely by 'believing' they are the right person — due care demands reasonable verification.

Mistake of Fact vs. Mistake of Law

The critical distinction: mistake of fact excuses; mistake of law does not. (a) Mistake of fact: I believe that the property I am taking belongs to me — but it actually belongs to someone else. If my belief was honest and based on reasonable grounds, I am not guilty of theft (which requires knowledge that the property belongs to another). (b) Mistake of law: I believe that the law allows me to recover my property by force. The law does not — only by legal process. I have no defence: every person is presumed to know the law. 'Ignorantia juris non excusat' — ignorance of the law is no excuse.

“To err is human — and the law acknowledges this. An honest mistake of fact, made with reasonable care, removes the guilty mind that criminal law requires. But ignorance of the law is never excused — the law's demands are public and accessible; the responsibility to know them falls on every person.”