Can You Be Blamed for Sleepwalking Crimes?

Nov. 28, 2009— -- A man strangles his wife while dreaming about fighting off intruders in his sleep. Does that make him mad, bad or innocent? Recent research is helping to unpick these issues, and may help reveal who, if anyone, bears responsibility in such cases.

Last week, British man Brian Thomas appeared in court on a murder charge after strangling his wife as they slept in their camper van.

The prosecution withdrew the charges after three psychiatrists testified that locking him up would serve no useful purpose. The judge said that Thomas bore no responsibility for his actions.

The case has cast a spotlight on the use of such sleepwalking defences in court.

"If you look at the media reports there appears to be an upsurge in the use of the sleepwalking defence," says Michel Cramer-Bornemann of the Minnesota Regional Sleep Disorders Center in Minneapolis.

Thomas had a genuine sleep disorder, but Cramer-Bornemann is concerned that in many other cases, the sleepwalking and other sleep-related defences are misused. Studies on the causes of sleepwalking may eventually make it easier to identify who has a genuine sleep disorder that could occasionally result in violence, and who is making it up.

Last month, Ursula Voss of Bonn University in Germany and colleagues reported that even during lucid dreaming – a state in which some people claim to be able to control their dreams – some areas of the brain associated with intent stayed offline, while other areas associated with consciousness were active.

"As long as you are in a dream, you have no free rein on your actions and emotions," says Voss.

Although this research didn't look specifically at sleepwalkers, it tallies with a previous study by Claudio Bassetti at the University of Zurich in Switzerland, who once managed to manoeuvre a sleepwalker into a brain scanner during a sleepwalking episode.

He found the sleepwalker also showed no activation in the areas of the brain associated with intent, though emotional areas and those associated with movement were active.

"Our judgement is off and our ability to act out emotionally is on," says Rosalind Cartwright of the Sleep Disorder Service and Research Center in Chicago. She believes a confirmed diagnosis of sleepwalking would make a strong defence in court, but says better tests are needed to establish who has a genuine sleep disorder.