Mens rea, in Anglo-American law, criminal intent or evil mind. In general, the definition of a criminal offense involves not only an act or omission and its consequences but also the accompanying mental state of the actor. All criminal systems require an element of criminal intent for most crimes. Only Anglo-American systems, however, employ the term mens rea. Countries such as France and Japan simply specify that there must be a criminal intent unless a specific statute directs otherwise.

Despite the evident importance of proper definition of the mental element, criminal statutes are frequently silent on what sort of mens rea, if any, must be shown. In other instances, a wide variety of terms are employed without any clear indication of how they are to be interpreted. The tentative draft of the American Law Institute’s Model Penal Code reduces the mens rea terms to four: criminals must act “purposely,” meaning that they must have an actual, consciously formed intent to achieve the criminal consequence; “knowingly,” meaning a conscious awareness that their conduct will produce the consequence; “recklessly,” meaning conscious disregard of the fact that their conduct is creating an unreasonable peril; and “negligently,” meaning inadvertence to peril that would have been apparent to a reasonable person.

In modern times a considerable body of penal offenses have been created in all countries in which no intent or other mental state