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The Doctrines of Mens Rea


The Doctrines of Mens Rea


As we saw in Chapter 2, criminal law is distinguished from all other fields of law because of the sanctions it can impose: loss of liberty and moral stigmatization. We regularly incarcerate, or otherwise deprive of freedom, persons who are not morally blameworthy—the mentally ill, the addicted, the fatally contagious, and so on. However, only criminal punishment declares that defendants are to blame for their acts; the essence of the judgment is not that they should be incarcerated for our sakes, but that they deserve punishment because they have chosen freely to violate the criminal law. Such a free choice appears to require that they knew what they were doing, and were aware, or at least risked, that it was morally blameworthy. For centuries, the law has captured this notion of free will and knowledge by looking for mens rea—Latin for “guilty mind.” This chapter is concerned with the basic definitions of mens rea.

Until 1900 or so many different terms were used to describe states of mind that seemed to reflect aspects of moral blame. However, behind each of these statutory terms stood the larger backdrop of mens rea itself: the broader notion of looking for a truly “immoral” person. We will refer to that notion as traditional mens rea. In the past century however the term “mens rea” has lost much of that moral connotation and has come to mean merely the mental state required by statute. We will call this statutory mens rea. Unfortunately, neither courts nor commentators differentiate consistently in their use of these concepts.

This chapter examines various aspects of mens rea: (1) defining the relevant mental states; (2) investigating the relation of mens rea to motive; and (3) interpreting statutes that use mens rea words. Succeeding Chapters 5 and 6 continue this exploration in the specific contexts of mistake and strict liability.

The Model Penal Code effected many changes in both the substantive criminal law and in the way criminal statutes are interpreted. Beginning with this chapter, the text will constantly compare and contrast the positions taken by the common law with those of the Code. This kind of comparison should help you understand both approaches. Although the MPC is “the” law in the majority of jurisdictions today, it cannot properly be understood without an awareness of how it differs from the common law and why its drafters took the approach they did.


Criminal law is not tort law. While that may seem obvious, the point is critical to understanding the central importance of mens rea to criminal law. Because tort law also deals with conduct that often results in physical injury, and because, historically, criminal and tort causes of action were joined in the same proceeding, it is helpful to contrast the two systems of law. In tort, where the prime aim is to compensate the innocent plaintiff, an objective standard (“the reasonable person”) is used to assess the actions of the defendant. Criminal law, however, has other concerns. Under most of the four theories of punishment discussed in Chapter 2, the defendant’s mental state is critical in determining whether to punish him. The entire theory of general deterrence—especially as articulated by its preeminent founder Jeremy Bentham—requires that the potential criminal “calculate” the gains and benefits of committing a crime and then choose to commit it. If the defendant does not know the punishment, or that the act is even criminal, the defendant is unlikely to be deterred. A utilitarian who seeks to rehabilitate the defendant needs to know whether the defendant needs “treatment,” which means that he knew—of was capable of knowing—the harm risked by his conduct. If so, then the defendant needs to be trained to avoid such injuries; if not, he needs to be trained to be aware of possible injuries.

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