Sleep Sex: Sexsomnia as a Criminal Defence

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Ella TrickeyJosh HarrisThe article Sleep Sex: Sexsomnia as a Criminal Defence is written by Josh Harris and Ella Trickey of Doogue + George Defence Lawyers.

Josh is an Associate at Doogue + George who specialises in contested summary hearings and contested intervention order applications. He was previously an associate to a County Court Judge and was a Senior Associate to the Criminal Reserve List.

Ella is one of our lawyers based at our Sunshine office. She appears regularly at the Sunshine Magistrates’ Court including other courts across Melbourne. Ella has a particular interest in Coronial jurisdiction and completed a professional placement at the Coroners Court of Victoria. She was also previously a Judge’s associate in the Supreme Court Criminal Division.

Man With Sexsomnia Using it as Criminal DefenceSexsomnia is a relatively new diagnosis in the field of psychology. It is also known as sleep sex, a condition that involves a person engaging in sexual activities while asleep, with no recollection of the event upon awakening. The condition is similar to sleepwalking and is characterized by the lack of conscious awareness and memory of the event. Sexsomnia is a medically recognised sleep disorder, first recognised as an official diagnosis in the 2013 edition of the DSM-5.

The nature of sexsomnia and the fact that it is a relatively new diagnosis means that there is limited research in this area. However, there is a growing number of studies supporting the view that it is a state where the individual has no volition, and any action performed is beyond the individual’s control. Australian courts have accepted the credibility and relevance of such studies in recent trials involving sexual offences (see e.g. R v DB [2022] NSWCCA 87).

There are a few examples of criminal cases in Australia and overseas where sexsomnia has been raised as a defence to charges of sexual assault or rape. In Australia, sexsomnia has been raised as the basis for a defence of automatism. Elsewhere, sexsomnia has been recognised in law as a form of mental impairment which is capable of giving rise to a verdict of not guilty by reason of mental impairment.

What is Automatism?

The principle that a person is not guilty of a crime if the act was not done willingly is fundamental in law. Automatism refers to a complete absence of control and direction by the accused’s will, and impaired or partial control is not enough to qualify as automatism. The presence of some awareness or cognition does not necessarily undermine the defence of automatism. The key consideration is whether there was a complete absence of deliberative mental functions, leading the accused to act automatically.

Automatism is a highly circumscribed legal concept, and courts have urged that it be viewed by juries with some scepticism, as it is easily raised but difficult to disprove. To establish a defence based on automatism, it must be demonstrated that the accused acted involuntarily, unconsciously, and with a total loss of control. The absence of conscious knowledge or memory of the events is often a prominent symptom of automatism, but mere memory loss does not automatically result in an acquittal based on automatism. Memory loss can have causes other than automatism.

The outcome of successfully raising the defence of automatism depends on the underlying cause. If it was caused by a “disease of the mind,” it is classified as “insane automatism,” and the appropriate verdict would be not guilty due to mental impairment. However, this verdict can only be given if the requirements for the defence of mental impairment are also satisfied. If the automatism was caused by something other than a “disease of the mind,” it is referred to as “sane automatism,” and the appropriate verdict would be an acquittal.

Examples of Cases Where Sexsomnia Has Been Raised as a Defence

The first example of a case where sexsomnia was successfully raised as a defence was the case of R v Spencer, a 2008 Northern Territory case. The accused, Spencer, was acquitted by a Northern Territory jury of charges of gross indecency and sexual intercourse without consent. During the trial, a psychiatrist provided evidence that Spencer was a regular sleepwalker. Southwood J, the judge in the case, informed the jury that they were entitled to accept the expert evidence suggesting that Spencer may have suffered from sexsomnia.

In R v Coulson [2010] VSCA 146, which took place in 2010, the Victorian Court of Appeal overturned the accused’s conviction on procedural grounds. Coulson had a history of sleepwalking and argued that the digital rape of a woman sleeping in a bedroom of his house was an unconscious and involuntary act. The central issue during the trial was whether Coulson was sleepwalking when he engaged in the allegedly unlawful acts. The conviction was initially overturned due to an error related to the expert evidence presented at trial. However, Coulson was later convicted after a second trial in 2011.

In TI v The Queen [2015] ACTCA 62, the appellant was tried and found guilty of incest and committing acts of indecency on a person under 16 years. The complainant in each case was the appellant’s 11-year-old stepdaughter. The appellant appealed the verdicts, arguing that they were unreasonable and that the possibility of him being asleep during the alleged offenses could not be reasonably excluded. Dr. Buchanan, a medical expert in sexsomnia, testified during the trial but conceded that there was no definitive test to diagnose sleep sex and that research into the phenomenon was still in its early stages. Another expert, Dr. Allnutt, also provided ambivalent evidence regarding whether the appellant’s actions were voluntary or a result of sexsomnia. The appeal was ultimately dismissed, with the court concluding that the guilty verdict was reasonably open to the jury based on the available evidence. The court recognized that the expert testimony raised the theoretical possibility of involuntary acts due to sleep state but highlighted that the credibility of the complainant and the appellant was crucial, making it a classic jury case.

Is Sexsomnia a ‘Mental Impairment’? The Canadian Approach

In Canada, sexsomnia is legally recognized as a mental impairment that can lead to a verdict of not guilty by reason of mental impairment.

The leading case in Canada is R v Luedecke.

In that case, the defendant attended a social gathering after consuming alcohol and magic mushrooms. After being awake for an extended period, he fell asleep and woke up in the midst of non-consensual sexual activity. Luedecke described feeling disoriented and shocked. When he learned of the police investigation into the assault, he voluntarily contacted them and provided a statement.

At trial, the court found that the defence of sane automatism had been established and acquitted Luedecke.

However, the Ontario Court of Appeal overturned the acquittal on appeal, leading to a new trial. The focus of the new trial was to determine whether Luedecke’s automatism should result in a verdict of not guilty or a verdict of not criminally responsible due to mental disorder. Luedecke ultimately consented to a finding of not criminally responsible on the grounds of mental disorder. The Ontario Review Board later granted him an absolute discharge after determining that he did not pose a significant threat to public safety based on the presented evidence.

This case clarified the classification of sleepwalking and similar disorders as “diseases of the mind” and provided guidance on the application of a legislative regime for mentally ill offenders established in 1992.

Is Sexsomnia Considered a Mental Impairment in Australia?

In Australia, individual states have enacted legislative frameworks that provide a structure for dealing with offenders who are deemed not criminally responsible for their actions due to the impact of specific mental health disorders. These regimes recognize that certain mental health conditions can affect an individual’s culpability for acts that would otherwise be considered criminal.1

The recent NSW case of R v DB [2022] NSWCCA 87 raised the question of whether sexsomnia qualifies as a mental impairment that can lead to a verdict of not guilty by reason of mental impairment. In this Crown appeal from a judge-alone trial, DB was charged with three counts of sexual intercourse with a child under the age of 10. He pleaded not guilty, claiming that his actions were involuntary due to sexsomnia, which he argued is not a mental health impairment under the Mental Health and Cognitive Impairment Forensic Provisions Act 2020 (NSW) (MHCIFP Act).

During the trial, the Crown acknowledged that the acts in question were involuntary. One of the issues on appeal was whether DB had a mental health impairment at the time of the acts. According to section 4 of the MHCIFP Act, a mental health impairment is defined as an ongoing disturbance of thought, mood, volition, perception, or memory that is clinically significant and impairs emotional wellbeing, judgment, or behaviour.

The trial judge determined that sexsomnia does not meet the criteria for a mental health impairment as defined in section 4 of the MHCIFP Act. The question on appeal was whether DB should have been subject to a special verdict of “act proven but not criminally responsible” under section 30 of the MHCIFP Act.

The Court, in its appeal decision, upheld the trial judge’s finding that sexsomnia does not qualify as a mental health impairment under the MHCIFP Act. It was concluded that the absence of volition during sleep, which is a universal characteristic, does not constitute a “disturbance of volition” as required by section 4(1) of the Act. Therefore, DB was deemed not to have a mental health impairment. The Court also emphasized that, based on common law principles, the acts of a person who is asleep and engaged in somnambulistic activity are not willed acts, and the accused is not legally responsible for them. Thus, the trial judge’s decision to grant DB an outright acquittal was considered appropriate.

Currently, there is no published authority in Australia for the proposition that sexsomnia is a mental impairment capable of giving rise to a verdict of not guilty by reason of mental impairment.


In conclusion, the legal defence of sexsomnia as a form of automatism raises intriguing questions about personal agency and accountability. Although it is a relatively new diagnosis, sexsomnia has gained recognition as a medically recognized sleep disorder in the field of psychology. However, due to limited research, the understanding of sexsomnia remains incomplete.

The legal implications of sexsomnia have been a subject of debate in various jurisdictions. In Australia, courts have accepted the credibility and relevance of studies indicating the lack of volition in sexsomnia cases. The defence of automatism, specifically sane automatism, has been raised in Australian courts in relation to sexsomnia, arguing that the actions were involuntary and beyond the individual’s control.

In Canada, sexsomnia has been recognized as a mental impairment capable of resulting in a verdict of not guilty by reason of mental impairment. However, in Australia, the question of whether sexsomnia qualifies as a mental impairment that can lead to a not guilty verdict by reason of mental impairment is still unresolved. The recent case of R v DB raised this question, but the court upheld the trial judge’s finding that sexsomnia does not meet the criteria of a mental health impairment under the relevant legislation.

[1] See e.g. Crimes Mental Impairment and Unfitness to be Tried Act 1997 (Vic)
Date Published: 7 June 2023

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