An Introduction to the Model Penal Code

by tylercook on November 7, 2013

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The modern penal code in the United States was developed in 1962 as a way to bring uniformity to the criminal codes of the different states (including the District of Columbia). Although not completely adopted by all states, the code led to changes and conformity in some aspects of criminal law from state to state. After the code’s creation in 1962, reform efforts were undertaken throughout the decade into the 1970s to improve the rule of law as it relates to criminal proceedings on the state level.

This discussion will focus on the history of the development of the modern penal code, areas of conformity among the 50 states and areas where states’ criminal codes still differ from the uniform effort of the modern penal code. We will also look at how federal and state laws compare and contrast with each other in light of the modern penal code.

The Development of the Modern Penal Code

Laws dealing with criminality and criminal behavior evolved at the state level, typically at the time a state was admitted to the Union. Other than the State of Louisiana, all laws conform to English Common Law (Louisiana’s laws operate under the French “Napoleonic Code”). The firm footing of English Common Law is rooted in the laws of the Old and New Testament, making the definition of good and bad straightforward. This patchwork of laws across the country prompted the need for a standard from which states and their legislatures could look to in order to revise their codes.

Work on the model penal code began in the 1950s as a project of the American Law Institute (ALI), an organization that was formed in 1923 to bring uniformity to American law. The ALI working group included legal practitioners from all aspects of the field, from practicing criminal attorneys to legal scholars and judges. The mission of the ALI, as stated, is “to promote the clarification and simplification of the law and its better adaptation to social needs, to secure the better administration of justice and to encourage and carry on scholarly and scientific legal work.” One of the most significant concepts that the model penal code developed was that of criminal intent to commit a crime. Known as mens rea, its existence is accepted nearly universally as an important element in determining motivation for criminal acts.

States that Have Adopted the Modern Penal Code

Work on the model penal code, or MPC, was completed in 1962. No state has adopted the law in whole, although New York State, New Jersey, and Oregon have adopted nearly all of the code. The State of Idaho initially adopted the MPC in its entirety in 1971 but repealed the law almost immediately after its acceptance. A total of 30 or so states have adopted portions of the MPC. It should be noted that the MPC is an advisory set of rules that lack any jurisdictional force, unless adopted by a state’s legislature.

Impact of Modern Penal Code on Criminal Law

The four elements of mens rea that are considered in order to assign degrees of criminal intent are whether the crime was committed (1) purposefully, (2) knowingly, (3) recklessly, or (4) negligently. The use of mens rea is important to assess a person’s culpability (intent to commit the crime) and is standard practice in criminal courts throughout the United States, particularly when addressing homicides.


Chris Bergstrom writes on a variety of complex legal topics including criminal defense, ID theft, the model penal code, legal history, constitutional law and others as well. Those concerned about their identity should give serious consideration to ID theft.




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