Is this question about Lady Macbeth purely academic fantasy? Hardly. Just ask Ron Voegtli. Ron Voegtli acted out his nightmares on a regular basis, subjecting his wife to abuse for thirty years. During the day, she said for ABC News, he was a wonderful man, but during the night there was no restraint on his behavior. An hour after going to bed, he would jump out and begin yelling and running around. He might grab a knife or other weapon as a means of protection. A few times he came into the bedroom and hit his wife, and once he grabbed her and tried to strangle her. Finally, Ron was introduced to Dr. Carlos Schenck at the Minnesota Regional Sleep Disorder Center. Fortunately, Dr. Schenck treated Voegtli with anti-convulsant drugs, which helped alleviate the symptoms. "He may have been running around the house like a wild maniac, but he's not a mental patient at all," Schenck said. "In the sleep lab … he demonstrated violent behavior during the delta stage of non-REM sleep. That is the stage where there is an alarm ringing in the nervous system of spontaneous, precipitous arousal that sets you off."
In fact, as reported in Psychology Today, “American history is littered with cases of sleepwalking killers – usually men who wake in the night and kill their wife or lover. The best-known historical case is that of Albert Tirrell, who, in 1845, killed his lover, Maria Bickford. They had been having an affair, and after being repeatedly caught by his wife’s family, he decided to kill Bickford and set fire to the building they were sleeping in – apparently to conceal the evidence of his crime. Unfortunately, the landlord was awoken by Bickford’s screams, and Tirrell was eventually caught and tried. He was acquitted of arson and murder, but found guilty of adultery. The rationale – provided by his use of the defense that he was asleep when he committed the murder and started the fire – was that he didn’t choose to kill Bickford, although he had chosen to continue his affair with her.”
Should we convict someone of something they did not voluntarily do? Hopefully even the most hardened prosecutor would say that convicting someone of something they did not do is wrong. Technically speaking, criminal law has long held that a conviction of a defendant for crime C is justified only if (1) defendant performs a voluntary act the performance of which is necessary for C’s occurrence (given the statutory definition of C) (Actus reus) and (2) the defendant had the mental purpose to commit the act (Mens rea).
Americans have fought and died to protect the presumption of innocence/proof beyond a reasonable doubt standards that are aimed at preventing conviction of people different from those who actually voluntarily committed the act to a relevant crime. Laws enshrine our abhorrence of punishment of the innocent, but that simple concept of not guilty unless you did the act voluntarily gets more difficult as the brutality or lack of social acceptance of an alleged crime increases. In those situations, the need to punish someone for such a terrible act may overwhelm the rational mind.
Clearly the need for a voluntary act is a fundamental prerequisite to criminal liability. This rule of law applies to persons who are not conscious of acting but who perform acts while asleep or while suffering from a delirium of fever, or because of an attack of epilepsy, a blow on the head, or any similar cause. California Criminal Jury Instruction 4.30. Automatism is a defense, not because of unconsciousness; the actors in these cases are not unconscious in any ordinary sense. It is also not because intent is lacking, or because the behavior does not amount to an action (the way that slipping and falling does not amount to an action) because the behavior in these cases is not random or accidental but purposive. Automatism is a defense because the action involved, while conscious and purposive, is not voluntary. The action is not voluntary because, although it involves what used to be called an act of will (being purposive), the act of will is itself caused by something beyond the actor's control—a blow on the head, a sleep disorder, epilepsy. Actions are not voluntary unless they are up to the actor, and actions that are caused by prior conditions are not up to the actor.