mistake of fact

Primary tabs

A mistake of fact is a mistake about a material factual element or mistaken belief other than a mistake of law. Examples include erroneous beliefs about the meaning of a legal term or about the identity of some person.

In criminal law, a mistake of fact can usually operate as a defense so long as it is reasonable. With crimes that require specific intent, even an unreasonable mistake of fact might work as a defense. 

The Model Penal Code §2.04 provides that “ignorance or mistake as to a matter of fact or law is a defense if: the ignorance or mistake negatives the purpose, knowledge, belief, recklessness or negligence required to establish a material element of the offense; or the law provides that the state of mind established by such ignorance or mistake constitutes a defense.”

Mistake of fact defenses are more likely to be successful than mistake of law defenses because the mistake of fact is more likely to negate the required mental state for the offense.

In contract law, a mistake of fact may be grounds for rescinding or modifying a contract.  A party that interprets a term one way, but has reason to know that another interprets it differently, should bring the issue to light before the contract is closed. Failure to do so often pushes courts to construe the meaning of the term against the party which had knowledge of the possible erroneous interpretation.

[Last updated in July of 2023 by the Wex Definitions Team]