Mens rea

Mens rea is a criminal law concept which focuses on the mental state of the accused and requires proof of a positive state of mind such as intent, recklessness, or willful blindness. In jurisdictions with due process, some level of mens rea is almost always a required element of the crime with which the defendant is charged, and must be proven by the prosecution, the exception being strict liability crimes or torts. Most civil law claims also incorporate some level of mens rea as a required element.

Mens rea comes from the Latin phrase; Actus non facit reum nisi mens sit rea, translated An act does not make a man guilty unless his mind be also guilty. Mens rea roughly translates to guilty mind.

An illustration of mens rea would be the difference between hurting someone voluntarily and accidentally; in the first case, the mens rea, the intention to hurt, is present but not in the second one.

Another example: if the intention to kill or to act in a way that can predictably lead to the death is not proved, one can not be found guilty of the crime of murder because the definition of this crime includes this condition (to be convicted, you need both the mens rea and the Actus reus, also known as the "psychological" and "material" elements); without the mens rea for murder, the accusation will usually turn into manslaughter, a different but similar crime that does not require the same mens rea.

Mens rea under the Model Penal Code

Prior to the 1960s, mens rea was a very slippery, vague and confused concept. Since then, the formulation of mens rea set forth in the Model Penal Code has been highly influential throughout North America in clarifying the discussion of the different levels of mens rea.

The four levels of mens rea set forth in the MPC are:

(1) Purposely - Express purpose to commit a specific crime against a particular person.

(2) Knowingly - Knowledge that one's actions would certainly result in a crime against someone, but did not specifically intend to commit that crime against the particular victim which one is accused of injuring. This also covers the concept of willful blindness. Willful blindness is where a person knows that something is very probable, but avoids investigating to gain that knowledge. Often used against drug mules, who knew that it was highly likely that there was contraband in the vehicle, but refused to look.

(3) Recklessly - Knowledge that one's actions had an unjustifiable risk of leading to a certain result, but did not care about that risk ("reckless disregard"), and acted anyway. It should be noted that under the MPC, barring contradictory statutory language, recklessness is the minimum mens rea that will lead to criminal liability. This covers the "depraved heart" state of mens rea, which is an extreme disregard for human life. Examples include playing Russian Roulette, street racing, and other highly dangerous activities.

(4) Negligently - Did not intend to cause the result that happened, but failed to exercise a reasonable duty of care to prevent that result (which includes failing to become aware of the risk of that result.) The above is the tort standard of negligence. In general this is not enough for criminal liability. Criminal negligence is a "gross deviation" from the standards of normal conduct and includes a substantial and unjustifiable risk. For example, one might be negligent for failing to put up a fence to keep children away from your pool. This will not lead to criminal charges. Criminal negligence might include keeping a vicious dog tied to a tree with twine.

Some commentators like to add on a fifth uncodified level, which exists in practice if not in the idealized Model Penal Code, which is, after all, merely a guide for states to follow in the development of their own criminal code. It should be kept in mind that the MPC is, in and of itself, not the law of the land anywhere, though many states have followed it to some degree or another.

(5) Strict liability - Strict liability is usually for "public welfare" offenses, like parking tickets, environmental regulations, and other such things. It is where the mental state of the defendant bears no relevance to the prosecution of the crime; the act itself is enough for conviction. Strict liabilty is rather rare in criminal law, but it does happen. For instance, statutory rape is a strict liability crime. Even if the defendant believed the girl to be over the age of consent, he is still guilty of statutory rape. As with all statements of the law, there are some jurisdictions that modify or ignore this rule. They are a minority. In most jurisdictions you are strictly liable for the age of the girl, even if she lied about it. The same is true other forms of child molestation.

Examples of mens rea in statutes

Model Penal Code: A person commits murder if he (1) purposely or knowingly (2) causes the death of a human being.

Common Law: (a) It shall be unlawful for a person to cause the death of a human being with malice aforethought. (b) A violation of this section is murder in the second degree.

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