"The engine is running, but there's no driver behind the wheel," was how one defence lawyer described it.

He wasn't talking about an out-of-control car, or a drunk driver.

He was mounting a defence in a rape trial, telling the court his client may have had sex with the woman he was accused of sexually assaulting, but he had no control over it, and no memory of it.

Sexsomnia may be a term that incites a schoolboy snigger, but for sufferers, and those close to them, it is a serious condition that can threaten relationships, and even land them in jail.


But increasingly, it's being used as a defence in rape cases worldwide.

In a headline-grabbing case out of the UK late last year, Lawrence Barilli was cleared of raping his partner because he was suffering sexsomnia.

His wife told the high court in Glasgow she would "wake up with him having sex with me ... I did not really not know what to think".

"I thought it was something that he was trying to spice up the relationship," she said, according to the Independent.

Barilla had insisted he had "no memory" of the incidents which she told the jury had occurred "a couple of hundred times".

When she asked him about it, he told her it was sexsomnia, diagnosed by his doctor.

The court returned a "not proven" verdict to the rape charges.


Experts say sexsomnia is a kind of "parasomnia", an abnormal behaviour which is exhibited while someone is in a deep sleep.

It's like sleepwalking, and night terrors, in that those who do it typically can't remember their actions.

During an episode, someone with sexsomnia might touch themselves while asleep, or try to have sex with someone near them.

Anecdotally, there are reports the person is more uninhibited and sexually insistent than they are when awake. And it's not great sex. More automated, and robotic, experts say.

Or as Barilla's wife said: "It was silent throughout ... I did not like it."

Dangerous ground: Experts say sexsomnia sufferers are on 'automatic pilot' when an episode hits. Photo / 123RF
Dangerous ground: Experts say sexsomnia sufferers are on 'automatic pilot' when an episode hits. Photo / 123RF

In one BBC article, a woman recalled two incidents with a man who unknowingly had sexsomnia (and thus didn't remember either encounter).

One night, he "began thrusting at her groin in a crude, unsensual kind of way".

During a later episode, he tried having penetrative sex through her underwear.

She considered leaving him, but then started asking some questions, genuinely puzzled by the out-of-character behaviour he told her he had no memory of, and his devastation that he had upset and hurt her.

A sleep clinic ultimately revealed he had sexsomnia.


Sexsomnia is quite rare compared to conditions like sleepwalking.

Sleepwalking affects about one in 25 kids, but 66 per cent of them grow out of it.

Sexsomnia, most often experienced by males, is much less common.

In fact, in 20 years of conducting sleep clinics, Victoria University associate professor Gerald Kennedy has "only seen four or possibly five genuine cases".

"People who suffer from sexsomnia are those who have an extended history of sleepwalking or other unusual sleep behaviours," he told Vice.

"The person isn't actually having sexual dreams, they're just acting automatically," he said.

"It's a real condition where someone can have sex without realising or wanting it and not remember anything."

Not many people, even doctors, know about it. It was added in 2013 to the Diagnostic and Statistical Manual of Mental Disorders.

A 2003 Toronto Western Hospital study found that 11 per cent of its male sleep-centre patients experienced sexsomnia, compared to just four per cent of female patients did.

Some factors think the numbers of sufferers are bigger, but those incidents aren't reported because sufferers are either too embarrassed to report it, or just don't remember it.


The idea that sexsomniacs are sleepwalking their way, zombie-like, to have their way is far-fetched.

Apparently, it's all about proximity.

"It's not likely that the person will wander out of their bed to have sex," Prof Kennedy said.

"It's more likely that when they're lying in bed with somebody they'll have a sexsomnia episode and have sex in their sleep."

And therein, lies the problem. And many victims. And several court cases.

"If you do have it and you share a bed with someone, and they wake up to you sexually assaulting them, then they'll probably have some complaints," said Prof Kennedy.

"So you have a duty of care towards them. It's like if someone had AIDS, they have to tell people they have it if they're going to have sex with them so they can take the appropriate precautions."

For sexsomnia to fly legally, a documented or diagnosed history helps.

Prof Kennedy warns also it may not mean offenders escape charges: "If I get drunk and I kill someone, I'm probably still going to be found guilty," he said.

"But it's going to affect the sentencing side of it. If I knew I had sexsomnia, and I sexually assaulted someone in my sleep, the judge would probably say: you knew you had this and you didn't warn the people around you. Therefore you would probably still be found guilty, but be punished more lightly."

In 2013, sexsomnia In Australia in 2014, amid concerns some sex offenders were feigning the condition to use it as a defence in court, the Australian Sleep Association moved to ensure doctors called to give expert testimony were well across the condition.

"It's a wake-up call that there are a lot more of these cases in the public media and therefore it's highly likely that this sort of defence — of sexsomnia and automatism — will be coming their way," Woolcock Institute of Medical Research medical director Dev Banerjee told Fairfax.


Sexsomnia has been used as a defence in rape trials in the UK for the past 15 years, and sporadically, in Australia, since 2008, when Leonard Andrew Spencer made history when found not guilty of rape after using "sex sleeping" as part of his defence.

The 48-year-old entered the bedroom of a guest at his home at Nhulunbuy in northeast Arnhem Land in the early morning of June 2007 and got into the 21-year-old's bed.

Mr Spencer, who claimed he had no recollection of the event, was accused of gross indecency and sexual intercourse without consent.

It's not great sex. More automated, and robotic, experts say. Photo / 123RF
It's not great sex. More automated, and robotic, experts say. Photo / 123RF

But his lawyer argued Mr Spencer was asleep at the time and depressed over his marriage breakup.

In the UK it has become such a regular defence in sex assault trials that prosecutors now sometimes don't even bring a case to trial if the defendant can prove they suffer from the condition.

Last month, The Irish Times forecast the defence would increasingly come into play in Ireland after the office of the Director of Public Prosecutions said it would not proceeding with the trial of a 31-year-old man accused of raping his friend after a night out while they shared a bed.

It was to be the third trial in the case, the publication said.

The first trial collapsed for legal reasons while the second resulted in a hung jury.

During those trials, the accused maintained he may have had sex with the woman but that it happened as a result of him suffering from sexsomnia,


While the cause of sexsomnia is still unknown, and the episodes are considered random, researchers think that people are triggered into them when there's a disruption in the brain as it moves between deep sleep cycles.

It's also thought sleep deprivation, alcohol consumption, or sleeping pills like Ambien increase someone's likelihood of experiencing sexsomnia.

Treatments can include medication to improve sleep, counselling, or avoiding triggers like alcohol and sleeping pills.

Dr David Cunnington, director of the Melbourne Sleep Disorders Centre says sexsomnia is "not indicative of people's true feelings" — it's a form of sleepwalking.

"Some people sleep walk, some talk, some eat and some initiate sex. It is not linked to deep-seated psychological issues or an indicator of mental illness," he said.

"It is just a failure of switching on/off all parts of the brain in synchrony on the border of wake and sleep."