Mens rea refers to criminal intent. The literal translation from Latin is ” guilty mind .” The plural of mens rea is mentes reae . Mens rea is the state of mind statutorily required in order to convict a particular defendant of a particular crime. Establishing the mens rea of an offender, in addition to the actus reus (physical elements of the crime) is usually necessary to prove guilt in a criminal trial . The prosecution typically must prove beyond reasonable doubt that the defendant committed the offense with a culpable state of mind . Justice Holmes famously illustrated the concept of intent when he said “even a dog knows the difference between being stumbled over and being kicked.”

The mens rea requirement is premised upon the idea that one must possess a guilty state of mind and be aware of his or her misconduct; however, a defendant need not know that their conduct is illegal to be guilty of a crime . Rather, the defendant must be conscious of the “facts that make his conduct fit the definition of the offense.” See: Staples v. United States, 511 US 600 (1994) .

Most states use the MPC’s classification for various mentes reae. The MPC organizes and defines culpable states of mind into four hierarchical categories:

Acting purposely – The defendant had an underlying conscious object to act.
Acting knowingly – The defendant is practically certain that the conduct will cause a particular result.
Acting recklessly – The defendant consciously disregarded a substantial and unjustified risk.
Acting negligently – The defendant was not aware of the risk, but should have been aware of the risk.

Thus, a crime committed purposefully would carry a more severe punishment than if the offender acted knowingly, recklessly, or negligently. The MPC greatly impacted the criminal codes of a number of states and continues to be influential in furthering discourse on mens rea.

Some have expanded from the MPC classification to include a fifth state of mind: strict liability . Strict liability crimes do not require a guilty state of mind. The mere fact that a defendant committed the crime is sufficient to satisfy any inquiry into the defendant’s mental state. This lack of a guilty mind would act as the fifth, and least blameworthy, of the possible mental states. For a strict liability crime, it is sufficient for the prosecution to prove that the defendant committed the wrongful act, regardless of the defendant’s mental state. Therefore, a guilty state of mind is irrelevant to a strict liability offense. Examples of strict liability offenses in criminal law often include possession and statutory rape . Many commentators criticize convicting defendants under strict liability because of the lack of mens rea.

Malice Distinction

A minority of states reject the MPC approach. Instead, they apply two levels of malice in order to ascertain the appropriate liability to apply to those who commit criminal acts.

Express malice – Commission of a crime with the deliberate intent to bring harm to the victim.
Implied malice – Indifference to harm that a victim may suffer due to the defendant’s carelessness or inattentiveness.