Mens Rea

History

A belief that an individual must have a “guilty mind” in order for his or her action to count as a crime has existed for hundreds of years, dating as far back as the Roman Empire. The term mens rea was not utilized in English common law, however, until around the mid-18th century. The basic premise underlying this concept is that in order for an individual to be found guilty of a criminal act, the perpetrator must have acted with a guilty mind, or mens rea. This is articulated by the Latin maxim actus not facit reum nisi mens sit rea (“an act does not make one guilty unless his mind is guilty”).

Ideas about mens rea found their way into American law in the latter part of the 18th century. By the time of the writing of the U.S. Constitution, the principles behind mens rea had already been integrated into general American law. As states gradually defined statutory law, mens rea was assumed; although it was not typically defined in the writings of the law, it was understood as common law.

During the Industrial Revolution, mens rea was incorporated in general law in public welfare offenses. Before this time, lawmakers and law officials were not concerned with why an individual committed a criminal act, but simply with the act itself. Additionally, they were not concerned with the intent of the offender, but that the prohibited act had been committed. With the implementation of various industry-related jobs and the dangers associated with them, however, society geared its public opinion toward the why instead of the how.

By the turn of the 20th century, an individual could be found to be criminally liable only if he or she was aware of the potential impact of his or her behavior. Thus, an injury caused without mens rea might be grounds for civil liability, but not for criminal prosecution. Even so, when the offense involves crimes such as violations of liquor laws and/or antinarcotic laws, motor vehicle laws, traffic-related laws, sanitary and building codes and regulations, and factory laws, offenders are held to be strictly liable, and proof of intent is not required.

Mens rea is an integral part of the criminal justice systems throughout the nation. In all 50 states and Washington, D.C., it is part of every criminal code. In the instance of premeditated murder, both mens rea and actus reus must be present to establish a guilty verdict. This can be clearly understood by examining the standards of mens rea and its components.

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