As an element of criminal responsibility, a guilty mind; a guilty or wrongful purpose; a criminal intent. Guilty knowledge and wilfulness.
A fundamental principle of CRIMINAL LAW is that a crime consists of both a mental and a physical element. Mens rea, a person's awareness of the fact that his or her conduct is criminal, is the mental element, and actus reus, the act itself, is the physical element.
The concept of mens rea developed in England during the latter part of the common-law era (about the year 1600) when judges began to hold that an act alone could not create criminal liability unless it was accompanied by a guilty state of mind. The degree of mens rea required for a particular common-law crime varied. Murder, for example, required a malicious state of mind, whereas LARCENY required a felonious state of mind.
Today most crimes, including common-law crimes, are defined by statutes that usually contain a word or phrase indicating the mens rea requirement. A typical statute, for example, may require that a person act knowingly, purposely, or recklessly.
Sometimes a statute creates criminal liability for the commission or omission of a particular act without designating a mens rea. These are called STRICT LIABILITY statutes. If such a statute is construed to purposely omit criminal intent, a person who commits the crime may be guilty even though he or she had no knowledge that his or her act was criminal and had no thought of committing a crime. All that is required under such statutes is that the act itself is voluntary, since involuntary acts are not criminal.
Occasionally mens rea is used synonymously with the words general intent, although general intent is more commonly used to describe criminal liability when a defendant does not intend to bring about a particular result. SPECIFIC INTENT, another term related to mens rea, describes a particular state of mind above and beyond what is generally required.