Crime Library: Criminal Minds and Methods

Automatism: The Sleepwalker's Defense



Sleepwalking usually occurs during the first third of the night and lasts half an hour or less, although longer episodes have been documented. Sleepwalkers generally go through familiar routines, but can be aggressive or violent. While this disorder is most common with developing children, it can last into adulthood. Half of all children have at least one episode, but only 5-9 percent of adults continue the habit. In fact, there are about eighty variations of sleep disorders, writes Jeff Stryker for's "Health and Body" section. Sleepwalking itself is a "parasmonia."

The idea is that normal physiological systems can be stimulated at inappropriate times. The brain issues commands and the muscles respond. Sleepwalkers might do nothing more than sit up or talk, or might behave in more complex activities such as cleaning the house or working on a project. If woken, they are confused and have no memory of what they've done. Ken Parks claimed he did not even recall turning himself in, but at some point in the process did wake up. The likely cause of a sleep disorder that involves overt behavior is the lack of release or uptake of a neurotransmitter responsible for inhibiting motor activity during sleep. In essence, his brain chemistry made him do it. Short of physical restraints, he had no conscious control over what he did.

Anglo-Saxon common law recognizes that criminal liability depends on two things:

  1. Actus reus — evidence that the accused could and did engage in a guilty act of commission or omission; and
  2. Mens rea — evidence that the accused had the required mental state to have intended to commit the act or to have foreseen its consequences

Triers of fact (judge or jury) must consider excusing behavior in those cases without both guilty act and intent, because our society accepts that the deranged or those lacking control or intent are not to be condemned in the same way as rational people who know what they are doing. To be convicted, the person must both have an evil mind and do an evil deed. The requirement of mens rea makes it possible to use abnormal mental states to absolve criminal guilt, but some defenses, from temporary insanity to forced drug intake to unconscious actions, make jury decisions about even physical responsibility complex.

For example, in 1955, a man inexplicably attacked his 10-year-old son. The man called his son to a window, struck him in the head with a mallet that threw the boy out the window, and then drove away. At some point, the man experienced a feeling that something dreadful had happened at home, so he drove back to the scene of the attack and was arrested. The defense at trial was that a brain tumor had caused a state of automatism, or a temporary trance, and thus, he could not be held responsible for actions it had caused. He was found not guilty, but not with an insanity acquittal. The man was considered to be psychologically healthy, just physically impaired at the time of the attack.

In some countries, automatism rebuts the actus reus component. That is, someone like Parks could not act voluntarily while not fully conscious. Not to be confused with an irresistible impulse, automatism is a neurological defense, unrelated to insanity. The behavior was never under the person's control. Thus, if acquitted, the accused is free to go. He or she does not have to go through treatment for an underlying disease. The defense does not work, however, if it can be shown that the defendant had experienced this condition on previous occasions and had not taken reasonable steps to remedy it. Let's see what those who study these disorders have to say.


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