Sleep Deprivation and Criminal Liability

Most criminal offenses involve a deliberate decision to perform an act that is proscribed by the criminal law. The criminal law requires the state to prove that the defendant committed a guilty act (actus reus), while simultaneously manifesting the necessary mental state (mens rea, or guilty mind) that is specified for that crime. Consider a case in which a person hammers to death a family member and then claims to have been asleep at the time of the attack. Because a guilty act must be voluntary, a question of fact arises concerning the person s consciousness and the effect that impaired consciousness, or indeed unconsciousness, has on voluntariness (4). In addition, consciousness bears on the guilty state of mind and is therefore relevant to the mens rea inquiry. 

The courts have grappled with how to apply the mens rea and actus reus requirements to defendants who are asleep or unconscious. The criminal law reveals two main categories of cases related to sleep deprivation. The first involves a situation where the act of falling asleep or losing consciousness causes harm, as in the case of a sleepy driver. The other concerns a person who, while asleep or unconscious, performs an act that causes harm, as in the case of a person who, while asleep, kills his roommate. Before discussing these categories in detail, we review the two essential elements of criminal liability and how they relate to sleep deprivation. 

This principle is firmly entrenched in the Model Penal Code (MPC), a model statute drafted by the American Law Institute in 1962 to help states define crimes consistently across the country (5). Many states have adopted the MPC, in whole or in part, and it has helped unify criminal law in the United States. The MPC recognized the incongruence of criminalizing actions performed by someone who is asleep or unconscious and incorporated that recognition into its definition of a voluntary act. Section 2.01 of the MPC states A person is not guilty of an offense unless his liability is based on conduct that includes a voluntary act 

In deciding whether to impose liability in respect of earlier choices made by the defendant, the courts will take into account a number of factors. The greater the risk of injury to others and the smaller the burden on the defendant to make less risky choices—the more a court will be inclined to impose criminal liability. In the case of intoxicated individuals, the risk analysis is clear. The risk of 

Canadian criminal law, like U.S. criminal law, recognizes a defense of automatism in cases where the defendant has acted in a state of unconsciousness. What makes the Canadian experience in this area particularly interesting is the very full discussion of the subject to be found in a number of court decisions, including a decision of the Supreme Court of Canada in the case of R. v Parks (23). After the Parks decision the issue of somnambulism arose in a number of provincial court decisions, in which concern over the use of the automatism defense in such cases was aired. 

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