Mens Rea refers to criminal intent. Moreover, it is the state of mind indicating culpability which is required by statute as an element of a crime. See, e.g. Staples v. United States, 511 US 600 (1994). Establishing the mens rea of an offender is usually necessary to prove guilt in criminal trial. In doing so, the prosecution 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.”
If a statute specifies a mental state for an offense, courts will usually apply the requisite mental state to each element of the crime. Moreover, even if a statute refrains from mentioning a mental state, courts will usually require that the government still prove that the defendant possessed a guilty state of mind during the commission of the crime. For example, the Supreme Court of the United States instructed that federal criminal statutes without a requisite mental state “should be read to include ‘only that mens rea which is necessary to separate” wrongful from innocent conduct.’”
Mental states are usually organized hierarchically by the offender’s state of blameworthiness. Generally, the blameworthiness of an actor’s mental state corresponds to the seriousness of the crime. For example, the Model Penal Code organizes and defines culpable states of mind into four hierarchical categories: purposeful, knowing, reckless, and negligent. Thus, a crime committed purposefully would carry a more severe punishment than if the offender was merely reckless. The Model Penal Code greatly impacted the criminal codes of a number of states and continues to be influential in furthering discourse on mens rea.
Although mens rea is a required element for most crimes, it is not for strict liability crimes. For a strict liability crime, it is sufficient for the prosecution to prove that the defendant committed the wrongful act. Therefore, a guilty state of mind is irrelevant to a strict liability offense. Examples of strict liability offenses in criminal law include possession and statutory rape. Many commentators criticize convicting defendants under strict liability because of the lack of mens rea. In contrast, the prosecution may applaud the relief from the burden of proving criminal intent.