Mens rea

Mens rea (/ˈmɛnz ˈriːə/; Latin for "guilty mind") is the mental element of a crime. It is a necessary element of many crimes.

The standard common law test of criminal liability is expressed in the Latin phrase actus reus non facit reum nisi mens sit rea, i.e. "the act is not culpable unless the mind is guilty". In jurisdictions with due process, there must be both actus reus ("guilty act") and mens rea for a defendant to be guilty of a crime (see concurrence). As a general rule, someone who acted without mental fault is not liable in criminal law. Exceptions are known as strict liability crimes.

In civil law, it is usually not necessary to prove a subjective mental element to establish liability for breach of contract or tort, for example. But if a tort is intentionally committed or a contract is intentionally breached, such intent may increase the scope of liability and the damages payable to the plaintiff.

In some jurisdictions, the terms mens rea and actus reus have been replaced by alternative terminology. In Australia, mens rea is now called "fault elements" or "mental elements" and actus reus is now called "physical elements" or "external elements". The point of the changes was to replace obscure Latin with simpler words.

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