Mistake (criminal law)

In criminal law, a mistake refers to an error or misunderstanding of fact or law that may negate a required element of a crime, such as mens rea (the guilty mind). A mistake can potentially serve as a defense to criminal liability, depending on the nature of the mistake, the specific crime charged, and the jurisdiction's legal rules.

Generally, there are two primary types of mistakes relevant to criminal law:

• Mistake of Fact: This involves an incorrect understanding of the factual circumstances surrounding the alleged crime. The crucial question is whether the mistake negates the mens rea required for the specific offense. For example, if a person takes another's umbrella believing it to be their own, they have made a mistake of fact that could negate the intent to steal, a necessary element of larceny. The mistake must be honest (genuine) and, in some jurisdictions, also reasonable. If the mistake is unreasonable, it may not provide a defense, especially for crimes requiring only a general intent.

• Mistake of Law: This involves an incorrect understanding or interpretation of the law. Historically, the maxim "ignorance of the law is no excuse" generally prevails, meaning that a mistake of law is typically not a valid defense. However, there are recognized exceptions. One notable exception is when a person relies on an official interpretation of the law, such as a judicial decision or an official statement by a government agency, which later turns out to be incorrect. Some jurisdictions also recognize a defense of mistake of law when the mistake negates mens rea, especially for crimes involving complex regulatory schemes where knowledge of the law's specific requirements is essential to establishing criminal intent.

The availability of a mistake defense often hinges on the specific intent required for the crime. Crimes requiring specific intent are more likely to be susceptible to a mistake defense because a genuine mistake can demonstrate the absence of the required mental state. General intent crimes are less likely to be successfully defended based on a mistake, particularly an unreasonable one.

The burden of proof generally rests on the prosecution to prove all elements of the crime, including mens rea, beyond a reasonable doubt. However, the defendant usually bears the burden of raising the mistake defense and presenting evidence to support it.