'But I was asleep through the whole thing, your honour': Sleepwalking isn't always comic; people can get hurt, writes Monique Roffey

'YOU PRAT,' was the last thought that went through Adrian Marler's mind a split second before he slammed into the wall. He had woken up an inch from it and realised, much too late, he'd been sleep-walking. He hit the wall with such force he broke his collarbone and woke the rest of the household.

They found him writhing on the floor in agony. 'I'd been dreaming that I was in a room with one door. I had to get through the doorway, which was blocked by footballers. So I ran at it pretty fast.' Another time Mr Marler flipped out of bed and landed so hard he chipped a vertebra in his back. His bed is now surrounded by two-foot walls.

Mr Marler is one of the estimated two per cent of the population that sleepwalks. However while Marler only hurt himself, some sleepwalkers, like Robert Burnett from Newcastle-upon-Tyne, can be more of a danger to other people. Last week 29-year-old Mr Burnett, a prison officer, was found not guilty of attempted rape after the court accepted that he was sleepwalking at the time.

It is estimated that about 15 cases of violent behaviour committed by sleepwalkers come to trial every year, ranging from GBH to murder or attempted murder. The perpetrators are all in the same position as Mr Burnett - having to ask the court to believe they cannot remember their crimes.

Sleepwalking often runs in families. Where there is no family history, it is normally associated with drugs, head injuries, infections or high temperature. It has three triggers: alcohol, over-tiredness and emotional upset. According to one of Britain's sleepwalking experts, Dr Peter Fenwick at the Maudsley Hospital, London, there are two forms of sleepwalking. The first, Stage Transition Disorder, happens when the changeover from Stage Four sleep (the deepest phase of non-dreaming sleep) to REM sleep (dreaming sleep) doesn't go smoothly. The person awakens slightly and can carry out various actions without consciousness.

The second type, REM Sleep Disorder, is when a person simply acts out his dreams during dreaming sleep. Normally when we sleep, we are in a state of paralysis. Here, paralysis is suspended.

Dr Fenwick says there are two hypotheses as to the level of consciousness of the sleepwalker. 'Either the person is quite conscious but his memory isn't working, so he can't store his actions in his memory. Or, the person is not conscious and therefore has nothing to store in his memory.' Either way, sleepwalkers can never remember what they've done while sleepwalking, which is their defence if they end up in court.

The longer a sleepwalk lasts, the nearer the person comes to a state of wakefulness and the more capable of complicated actions. Some of Dr Fenwick's patients have done very strange things in their sleep. 'I've had people who've ridden horses and motorbikes, driven cars, made breakfast, stripped wall paper, mended the fridge, you name it.'

The violent sleepwalker's plight is clearly much more serious. Barry Burgess viciously attacked his girlfriend one night while alleged to be sleepwalking. It proved a watershed case. On 19 July 1989, the Judge who presided over the case, Sir Ian Lewis, ruled at Bristol Crown Court that sleepwalking met the legal requirements for 'insane' behaviour and Mr Burgess was sentenced to an indefinite stay in a psychiatric hospital.

Before this ruling, the law regarded sleepwalking as a simple, automatic activity: as they were unaware of their actions, offending sleepwalkers were allowed to walk free from court. Now judges have the option of confining them to a psychiatric hospital. Although Robert Burnett pleaded not guilty by reason of insanity, he was put on probation for two years and not put into psychiatric care.

Dr Fenwick has a set of guidelines to help sleepwalkers. 'Avoid sleeping in strange places,' he says. 'Also avoid getting over-tired, and avoid alcohol or emotional tiffs, before bedtime. Make sure you put the key to the room in a place where you can find it when you're awake, not when you're sleepwalking.'

He advises wives with partners who become very violent when they sleepwalk to sleep in a different room. One tip most experts agree on is to avoid frightening and confusing the sleepwalker by waking him. Instead gently guide him back to bed. Or, like Adrian Marler, you can always consider putting your bed in a box.

(Photograph omitted)