Element (criminal law)

The basic components of an offense are listed below; generally, each element of an offense falls into one or another of these categories. At common law, conduct could not be considered criminal unless a defendant possessed some level of intention – either purpose, knowledge, or recklessness – with regard to both the nature of his alleged conduct and the existence of the factual circumstances under which the law considered that conduct criminal. However, for some legislatively enacted crimes, the most notable example being statutory rape, a defendant need not have had any degree of belief or willful disregard as to the existence of certain factual circumstances (such as the age of the accuser) that rendered his conduct criminal; such crimes are known as strict liability offenses.

Mental state (Mens rea)

Mens rea refers to the crime's mental elements of the defendant's intent. This is a necessary element—that is, the criminal act must be voluntary or purposeful. Mens rea is the mental intention (mental fault), or the defendant's state of mind at the time of the offense, sometimes called the guilty mind. It stems from the ancient maxim of obscure origin, "actus reus non facit reum nisi mens sit reas" that is translated as "the act is not guilty unless the mind is guilty." For example, the mens rea of aggravated battery is the intention to do serious bodily harm. Mens rea is almost always a necessary component in order to prove that a criminal act has been committed.

Mens rea varies depending on the offense. For murder, the mental element requires the defendant acted with "malice aforethought". Others may require proof the act was committed with such mental elements such as "knowingly" or "willfulness" or "recklessness". Arson requires an intent to commit a forbidden act, while others such as murder require an intent to produce a forbidden result. Motive, the reason the act was committed, is not the same as mens rea and the law is not concerned with motive.

Although most legal systems recognize the importance of the guilty mind or mens rea, exactly what is meant from this concept varies. The American Law Institute's Model Penal Code has reduced mental states to four. In general, guilt can be attributed to an individual who acts "purposely", "knowingly", "recklessly", or "negligently." Together or in combination, these four attributes seem basically effective in dealing with most of the common mens rea issues.