Could You Commit Crimes In Your Sleep?

Murder, Rape, and Other Offenses Have Been Blamed on Parasomnias

A man sleepwalks up some stairs. Image Source/Getty Images

It seems like an attractive defense if you are trying to get out of a crime: “But officer – I was asleep!” In fact, this defense was first used more than 100 years ago. Could it be possible to commit crimes while remaining asleep? Learn about a field called sleep forensics, how sleep behaviors called parasomnias may have a role, and why it is difficult to hypothesize in hindsight what might have occurred.

The Wacky World of Sleep Forensics

It may sound like an episode of your favorite serial crime drama, but there is actually an area of medicine concerned with sleep forensics. Though not widely practiced (or needed), these sleep physicians have an expertise in abnormal sleep behaviors. They understand the science of the conditions as well as the legal implications of the resulting activities.

The most sensational cases within sleep forensics involve murder. Suspects have committed rather elaborate crimes and have, after the fact, claimed to have been unaware of their actions and asleep. Could such a thing occur? How does an expert witness determine what happened?

Sleep Behaviors and the Realm of Possibility

Parasomnias include many different sleep behaviors that result due to mixed states of consciousness. The person is partly awake and able to move around, but may be unaware of their actions due to persisting unconsciousness.

These conditions may include:

If you can do it during the day, there is a possibility that you may be able to do it during sleep. These behaviors may occur due to wakefulness mixing with both Non-REM and REM sleep.

Other Dream-enactment Movements

Some of these acts may be provoked by the use of sleeping pill medications that suppress consciousness and memory formation by the hippocampus. The most commonly used hypnotic medication provoking such behaviors is Ambien. It is a known side effect of the drug, and may require discontinuation of its use.

Though these mixed states of consciousness can provoke elaborate behaviors, it is difficult to prove that such a state was occurring during an alleged crime. In some cases, the behavior may be deemed to be too elaborate or potentially disruptive of preserved sleep. There may be elements of rationale thought, such as cleaning up a crime scene, that are unlikely to occur when asleep. 

Though a diagnostic polysomnogram may identify the risk of experiencing parasomnias, as well as some provocative factors such as sleep apnea, this may not be definitive evidence to excuse a crime. In order to reach a just conclusion, careful expert testimony must be weighed in the context of other factors. 


Kryger, MH et al. "Principles and Practice of Sleep Medicine." ExpertConsult, 5th edition, 2011.

Sleep Forensics Associates. Last accessed: March 31, 2015.

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