Is ‘sexsomnia’ a genuine medical disorder or the latest ‘get out of jail free card’? As its use as a legal defence grows, experts are raising alarm over its potential misuse.
In 2011, Joseph Short was found not guilty of raping and physically assaulting a Scottish woman whom he was having a relationship with. Two years later, Andrew Machin, 40, was cleared of raping a 21-year-old women at a Butlins Holiday camp. In 2019, Dale Kelly was acquitted of sexually assaulting his friend’s partner after entering the couple’s bedroom and groping the woman after an evening of drinking.
Each of these cases relied on the controversial defence of ‘sexsomnia’ – a rare sleep disorder in which individuals engage in sexual behaviour while in a ‘sleepwalking state’. Courts accepted this defence in all three instances, granting the defendants full acquittals with no further intervention.
Sexsomnia is classified as a form of parasomnia, a group of sleep disorders that occur when your brain is caught between different stages of sleep. Dr Guy Leschziner, a neurologist and sleep disorder specialist defines it as, “a state in which there is essentially discordance or disagreement between different parts of the brain as to what stage of sleep or wake you’re actually in.” Sleepwalking is still a fairly misunderstood area of sleep.
Dr. Leschziner highlights that during sleepwalking, certain areas of the brain associated with wakeful activities – such as movement, vision and emotion – remain active. “Whereas the parts of the brain that are most likely not active are the parts responsible for memory, which is why memory seems to be completely absent or very diminished.”. This lack of memory and conscious control is central to the defence of automatism, which only requires the opposition to raise the question of reasonable doubt rather than prove a sleepwalking episode.
So, if you rape someone whilst your asleep, are you guilty? If your eyes are open but half your brain is asleep, are you guilty? Could sexsomnia be the perfect defence?
Dr John Rumbold, a law lecturer at Nottingham Trent University and author of ‘Automatism as a Defence in Criminal Law’, says: “It’s very often drunk young men who say they have sexsomnia. If you drink enough, you will have an alcoholic blackout where you can’t remember what happened, and off course alcohol is no defence to rape. So these people have no defence at all.” Alcohol is widely recognised as a ‘disruptor of sleep’, with its effects varying between individuals. Dr. Rumbold emphasises that under British law, the more alcohol consumed, the less credible a sleepwalking defence becomes.“My worry is, there’s a lot of dodgy sexsomnia defences. You have to think about the negative side of all those people not getting justice”.
An investigation in 2024 by The Observer uncovered a sharp rise in the use of the ‘sexsomnia’ defence. While there were occasional cases in the 1990s and 2000s, at least 51 have been recorded in the last decade alone. Notably, juries returned not guilty verdicts in 60% of cases where sleepwalking was used as part of the defence. With the conviction rate for rape falling to just 51% in the first quarter of 2024-2025, could the sleepwalking defence be contributing to these poor prosecution rates?
So, how can we prove whether someone was sleepwalking? The short answer is you can’t, at least not 100%. Dr Liezenchers explains that the only ‘definitive’ way to confirm sleepwalking would be to have an individual connected to an EEG at the time of the crime – something he describes as ‘essentially impossible’. “It’s extrapolation rather than proof”. Medical expert witnesses must instead rely on factors that might indicate a parasomnia state: “have they got proceeding history of sleepwalking that has been witnessed by somebody else, where the actions exhibited in keeping with sleepwalking or did they demonstrate a high degree of planning.” In cases of alleged sexsomnia, specific factors such as seeking out the victim, denying the act, having a motive or having sexual attraction to the victim are closely scrutinized. Even when someone has a predisposition to sleepwalking, this alone does not prove that the alleged crime occurred during one of these episodes. Sleepwalking is rare in adults, affecting only an estimated 1-2% of the UK population.
Dr Leizencher, author of ‘The Nocturnal Brain: Nightmares, Neuroscience and the Secret World of Sleep’, has lent his expertise in cases involving claims of sleepwalking and sexsomnia. He says: “I’ve seen some people do some very very unusual and strange things, including violence, including sexual behaviour, that I’m very firmly convinced happened whilst they were in a non-REM parasomnia state.” While he believes that sexsomnia provides a valid defence in criminal cases, he suggests that due to the unavailability of definite proof, it can provide a ‘convenient excuse’.
Sleepwalking as a defence is not new. The first successful use dates back to 1846, when Albert Tirrell was found not guilty of murdering a woman despite slitting her throat from ear to ear. Since then, the sleepwalking defence has fallen under the broader category of automatism; which argues a defendant cannot be held culpable if unaware of their actions when they committed a crime.
The automatism defence is divided into two categories: insane (internal) and non-insane (external) automatism. If a defendant successfully raises the defence of insane automatism, they can be found “not guilty by reason of insanity,” leading to outcomes such as a hospital order, a supervision order, or an absolute discharge. Sleepwalking can fall under either category, and it’s ultimately up to the judge to determine which defence will be used. Dr John Rumbold, who is also a member of the British Sleep Society, says: “With sleepwalking generally, the feeling in the past is that the person couldn’t help themself and it’s very unlikely to happen again.” However, this perception often leads to a lack of protective measures being implemented for both the public and the defendant. The case of Joseph Short illustrates such risks of the approach. After being found not guilty of rape and assault under the non-insane automatism defense, Short went on to reoffend twice. He was ultimately found guilty of raping one victim and sexually attacking another whom he pursured on a bike. He claimed to be sleepwalking in both instances.
Alison Summers KC, a Barrister and Head of Drystone Chambers, suggests that the ‘‘supposed sudden increase’ is not as it seems. “I think what’s important is we don’t lose sight of the fact there are some very genuine cases, where people do suffer from what is a very serious and quite distressing medical disorder that can have massive consequences both for them and obviously for a victim.” Of the few cases Summers has run to trial, all defendants have received a full acquittal. In one of her most recent cases in 2022, she successfully defended a young man accused of raping his partner.
The couple who had a ‘good relationship’, went to bed after having consensual sex. They fell asleep naked, and the woman awoke to find him on top of her. The victim claimed it felt as though ‘he just wasn’t with it’. The man, who had no recollection of the incident, broke down crying during his arrest interview as he ‘couldn’t understand what had happened’. Further investigation revealed that his brother also exhibited similar sleep behaviours, with his wife confirming that her husband had been engaging in sexual acts like this for years. “That was a classic example of when you have really strong evidence of this disorder.” says Summers.
Dr Rumbold argues that the main issue with the sexsomnia defence lies in the role of the expert witness. “Some of the expert witnesses that testify aren’t really expert expert witnesses”, highlighting the ‘surprisingly lax’ rules that govern who is qualified to provide testimony. For those working in the NHS, getting time off work is difficult and it isn’t that well rewarded. “People who do have time are those who are retired, but then you have the slight issue that because they are retired, they are not necessarily as up to date on all the latest research.”
Alisson Summers furthers this by pointing out that many of the expert witnesses have expertise in the wrong areas. She believes some ‘less scrupulous cases’ are making their way into the crown court due to individuals with psychological backgrounds ‘advertising’ themselves as experts.“This isn’t a psychological or psychiatric condition, this is a medical condition”, she says.
Many experts have argued that the law is not doing enough to safeguard victims and prevent the defence from being misused. Summers believes the current distinction between insane and non-insane automatism is ‘out of date’ as the courts are yet to catch up with developments in medical science. She suggests making it mandatory for sleepwalking cases to be tried under the insanity defence. Dr Rumbold also proposes the idea of judge-imposed sexual prevention orders. While he admits this wouldn’t be as ‘satisfying’ as a conviction, it would at least implement some protection. “At the end of the day, there’s a victim there, regardless of whether the person is found criminally guilty, there’s still a victim there.”
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