What is 'sexsomnia,' the condition in which a person unconsciously engages in sexual activity while sleeping?

'Sexsomnia' is a sleep disorder in which a person unconsciously engages in sexual activity while sleeping. Christopher Rudge, a law researcher at the University of Sydney, explains the legal issues surrounding sexsomnia.

What is sexsomnia? And how can it be used as a defense in court?
https://theconversation.com/what-is-sexsomnia-and-how-can-it-be-used-as-a-defence-in-court-248756

Sexsomnia is a type of sleep disorder in which a person unconsciously engages in sexual contact, intercourse, masturbation, etc. while sleeping. It was added to the DSM-5 , which compiles the diagnostic names and diagnostic criteria for mental illnesses, in the 2013 update .

Sexsomnia is reported to be caused by alcohol intake, stress, etc. Although a total of 116 cases of sexsomnia have been reported as of 2020, it is possible that some patients have not reported their condition because they are embarrassed to visit a doctor or do not realize that they have sexsomnia.

In sexual assault trials, defendants may plead not guilty due to sexsomnia. For example, in January 2025, a man was tried in Australia for 'engaging in non-consensual sexual acts with a woman at his home,' but was found not guilty because he suffered from sexsomnia and engaged in the act while unconscious. In this trial, the fact that the man suffered from sexsomnia was treated as a fact, and the issue at issue was whether the man was conscious at the time of the incident.

Man with 'sexsomnia' not guilty of raping woman after judge warns jury in Sydney trial | Australia news | The Guardian
https://www.theguardian.com/australia-news/2025/jan/30/timothy-malcolm-rowland-sexsomnia-not-guilty-rape-sydney-ntwnfb

According to Rudge, sexsomnia is legally treated as a 'temporary mental dysfunction,' and if it were proven that sexsomnia is a 'mental disorder,' it would be difficult for the defendant to win an acquittal. In Australia, if a person with a mental disorder commits a crime, they will be sent to a mental health court rather than being acquitted.

In fact, in 2022, a lawsuit was filed in Australia seeking to have sexsomnia considered a 'mental disorder' rather than a 'temporary mental dysfunction,' but the plaintiffs were unable to prove that sexsomnia is a mental disorder. In this lawsuit, some judges argued that sexsomnia could be legally considered a mental disorder because 'the purpose of the new mental health law is to protect public safety,' but the majority of the courts argued that 'humans cannot have wills while asleep, and sexsomnia cannot be considered a mental disorder in light of the relevant laws.'

However, in Canada, sexsomnia is legally considered a mental disorder, meaning no one can be found innocent on the basis of sexsomnia, and accused people are subject to mental health evaluations.

Among the points that can't be made in 800 words is that the Canadian position is different. There, sexsomnia is a mental health impairment, which means that an outright acquittal is not available and a defendant who pleads the defense will be subject to mental health review. …

— Christopher Rudge (@chrisrudge) February 5, 2025

'The increasing use of sexsomnia as a defence in serious and violent sexual assault cases is worrying and calls for further research and attention into sexsomnia,' Rudge said.