Summary An increasing number of criminal cases have claimed the defendant to be in a state of sleepwalking or related disorders induced by high quantities of alcohol. Sleepwalkers who commit violent acts, sexual assaults and other criminal acts are thought to be in a state of automatism, lacking conscious awareness and criminal intent. They may be acquitted in criminal trials. On the other hand, criminal acts performed as the result of voluntary alcohol intoxication alone cannot be used as a complete defense. The alcohol‐induced sleepwalking criminal defense is most often based on past clinical or legal reports that ingestion of alcohol directly ‘triggers’ sleepwalking or increased the risk of sleepwalking by increasing the quantity of slow wave sleep (SWS). A review of the sleep medicine literature found no sleep laboratory studies of the effects of alcohol on the sleep of clinically diagnosed sleepwalkers. However, 19 sleep laboratory studies of the effects of alcohol on the sleep of healthy non‐drinkers or social drinkers were identified with none reporting a change in SWS as a percentage of total sleep time. However, in six of 19 studies, a modest but statistically significant increase in SWS was found in the first 2–4 h. Among studies of sleep in alcohol abusers and abstinent abusers, the quantity and percentage of SWS was most often reduced and sometimes absent. Claims that direct alcohol provocation tests can assist in the forensic assessment of these cases found no support of any kind in the medical literature with not a single report of testing in normative or patient groups and no reports of validation testing of any sort. There is no direct experimental evidence that alcohol predisposes or triggers sleepwalking or related disorders. A legal defense of sleepwalking resulting from voluntarily ingested alcohol should be consistent with the current state of art sleep science and meet generally accepted requirements for the diagnosis of sleepwalking and other parasomnias.

Parasomnias are defined as unpleasant or undesirable behavioral or experiential phenomena that occur predominately or exclusively during the sleep period. Initially thought to represent a unitary phenomenon, often attributed to psychiatric disease, it is now clear that parasomnias are not a unitary phenomenon but rather are the manifestation of a wide variety of completely different conditions, most of which are diagnosable and treatable. The parasomnias may be conveniently categorized as "primary sleep parasomnias" (disorders of the sleep states per se) and "secondary sleep parasomnias" (disorders of other organ systems, which manifest themselves during sleep). The primary sleep parasomnias can be classified according to the sleep state of origin: rapid eye movement (REM) sleep, non-REM (NREM) sleep, or miscellaneous (i.e., those not respecting sleep state). The secondary sleep parasomnias can be further classified by the organ system involved. The underlying pathophysiology of many parasomnias is state dissociation-the brain is partially awake and partially asleep. The result of this mixed state of being is that the brain is awake enough to perform very complex and often protracted motor and/or verbal behaviors but asleep enough not to have conscious awareness of, or responsibility for, these behaviors.

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