This week a York man was cleared of raping a woman because a jury believed he was sleepwalking at the time of the alleged assault. Health Editor Barry Nelson investigates the strange phenomenon of somnambulism.

IN the dead of night Ken Parks rose from his bed, got dressed and found his car keys. He went out to his car, started the engine and drove the 14 miles from his home in the Canadian city of Toronto to where his parents-in-law lived. It was still night time when he pulled up outside their home.

By the time dawn broke, Ken Parks had stabbed his mother-in-law to death in what was described as a violent, unprovoked and apparently motiveless attack. Parks was put on trial for murder but was acquitted on the grounds that he had been asleep at the time of the attack.

The case of Ken Parks, which happened in 1987, was cited by defence lawyers during a much more recent case in the North-East.

On Tuesday, James Bilton, 22, from York, was cleared of three charges of rape by a jury at York Crown Court. It followed a week-long trial at which sleep expert Dr Ishaad Ebrahim gave evidence on his behalf.

Mr Bilton's defence was that he could not remember the alleged attack at his flat in York and that he must have been sleepwalking.

During the trial, the jury was told that the woman knew Mr Bilton and after a night out with her in March this year, he put her to bed in his flat while he slept on the sofa. Later, the 22-year-old woman claimed she woke to find her trousers had been taken off and that Mr Bilton was assaulting her. The woman denied that she had consented to sex.

Mr Bilton said he had no knowledge of the attack but that he had a history of sleepwalking, which ran in the family. He told the court that he was "completely oblivious" to what had allegedly happened.

Dr Ebrahim testified that Mr Bilton did suffer from the condition and told the jury that people who are sleepwalking can carry out actions which they do when awake.

Between one and 2.5 per cent of the adult population suffer from the condition. Of those, four per cent carry out sexual activity while they are still asleep.

Mr Bilton's acquittal followed a similar case in Canada. Just last month, Jan Leudecke, 33, was acquitted of raping a woman after a judge ruled that he was asleep during the attack

At Mr Leudecke's trial, sleep experts and psychiatrists testified to a condition called "sexsomnia", when a person has sex while they are still asleep.

In another court case in 1996, a Canadian man was acquitted of killing his wife after it was determined that he had been sleepwalking.

Anyone searching the internet for more information about sleepwalking will undoubtedly come across the Sleepchannel, part of an American website called Healthcommunities.com. Offering medical advice on a range of health problems, Sleepchannel, as its name suggests, concentrates on problems relating to sleeping.

According to the website, sleepwalking (or somnambulism) affects up to 17 per cent of children and is more frequently seen in boys. The good news is that sleepwalking seems to decrease with age, but Sleepchannel claims that the prevalence among adults is as high as ten per cent. The activity is said to take place when sleepers begin to move, usually by walking, during deep sleep.

Sleepwalkers are said to be usually unaware of their activity. The website says that some cases of autonomic (independently functioning) behaviour such as dressing and eating can occur.

According to Sleepchannel, the cause of sleepwalking is not known, though most people have sleepwalked on at least one occasion.

The site suggests that sleepwalking poses no serious health threat to those who experience it, although the risk of injury is a matter of concern.

Injury prevention, the website says, is the primary objective of sleepwalking management.

Those who are asked to treat sleepwalking usually recommend the following safety measures: locate the bedroom on the ground floor, lock the windows and cover them with heavy curtains, keep the floor clear of harmful objects, remove sharp objects from the room, stay on the first floor when visiting others and when sleeping at a hotel.

Treatment for this condition is said to be often unnecessary but in cases where the problem occurs frequently and has involved violence or injury, drugs such as benzodiazepine or antidepressants can be prescribed.

Other approaches to treatment include biofeedback (the use of electronic monitoring to train someone to acquire voluntary control of a normally automatic bodily function), and hypnotism.

Sleepchannel stresses that sleepwalking does not indicate mental dysfunction.

In his book "Counting Sleep: The Science And Pleasures Of Sleep And Dreams", published by Flamingo in 2003, acclaimed science writer Paul Martin devotes several pages to sleepwalking.

He points out that sleepwalking is the product of so-called NREM (Non-Rapid Eye Movement) sleep as opposed to REM (Rapid Eye Movement) sleep. It is during REM sleep that humans dream.

According to Martin: "Sleepwalking and sleeptalking are products of slow-wave NREM sleep, not REM sleep. The muscular paralysis that accompanies REM sleep would prevent the sleeper from walking or talking."

Martin says that sleepwalking results from "a glitch in the mechanisms controlling arousal; in effect, the mind and body fail to wake up in synchrony".

He points to the results of a large survey which found that sleepwalking was more prevalent among people who had suffered a stressful event such as a road accident within the previous year.

"Regular sleepwalkers tend to have more disturbed sleep, containing more microarousals, during the first sleep cycle of the night," says Mr Martin.

Sleepwalking can run in families. In 1930 a scientist documented a family of six who were all sleepwalkers.

Mr Martin quotes fellow scientist William Dement telling the story of a family of sleepwalkers who all assembled in the dining room at the same time in the middle of the night. Their nocturnal gathering was only confirmed when one of their number woke up.

"According to another tale, a lady awoke one night with the disagreeable sense of not being alone... the lady was terrified and fainted. When she regained consciousness in the morning she found that her butler, in a fit of sleepwalking, had laid the table for 14 people upon her bed," writes Mr Martin. While he stresses that the vast majority of sleepwalkers do not require medical help, he points to a survey which suggests that two per cent of Britons have behaved violently while asleep, usually during sleepwalking.

"The survey also revealed that these sleepwalkers consumed above-average amounts of caffeine, tobacco and alcohol, and had a higher incidence of mood and anxiety disorders," says Mr Martin.

The idea that sleepwalkers can respond to hypnosis is familiar to North-East hypnotherapist and motivation coach, Matt Hudson, who regularly uses the techniques on somnambulist clients.

Mr Hudson believes that sleepwalking is related to unresolved issues in dreams.

"Some people have recurring dreams or nightmares. If it involves an intruder in their room they will get out of bed and try to get away from whatever is bothering them. They can come down the stairs or try to open their front door to get out, which can be very frightening for other people."

Mr Hudson, a self-taught hynotherapist and 'mind coach' who has achieved impressive results working as a motivation coach with businesses, says: "You use hypnosis to create a dream-like state so you can communicate with them and help them to understand their dream."

Once they have a conscious understanding of their dream, it usually vanishes, along with the sleepwalking problem, says Mr Hudso n, who holds regular clinics in North Shields.

While James Bilton walked free from court this week, the issue of whether sleepwalkers are liable for their actions is likely to surface again.

* To contact Matt Hudson visit his website, www.matthudson.org or telephone 0191-236 9800.