mistake of law

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A mistake of law is a mistake about the legal effect of a factual situation. Pointing to a mistake of law almost never works as a criminal defense unless the relevant criminal statute requires the state to prove knowledge of the illegality of the offense. One exception where mistake of law may be successful as a defense is when a criminal defendant relies on a misstatement of the law in a statute, judicial opinion, or official statement from an executive officer. 

A mistake of law differs from a mistake of fact, which is a mistake about a material fact and is more likely to operate as a defense in criminal law. A mistake of law is also known as an error in law or error of law.

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