Sexsomnia and the Criminal Law

6 May 2021

‘Sexsomnia’ or ‘sexomnia’ is a form of parasomnia. A parasomnia is an undesirable behaviour arising from sleep. Common examples including sleep walking and sleep talking. Sexsomnia is a less common, but sometimes more problematic example of a parasomnia, which involves sleep related sexual behaviour.

Sexsomnia describes behaviour where individuals who, due to being asleep, have no conscious control over their actions and engage in activities such as sexual vocalisation, masturbation, touching, thrusting or intercourse. There appears to be a particular prevalence of anecdotal reports of parasomnial behaviour, or sexsomnia on long haul flights, where a passenger may be disorientated by a combination of disturbed sleep patterns, time zones and/or alcohol and sleeping aids.

In these circumstances of sexsomnia, the individual nearly always has no recollection of the incident. To a third party, the person who is subject to the parasomnia may appear to be awake, conscious and in control of their actions. The consequences for the complainant and suspect in cases like these are significant. The legal issues do not centre on consent, as none has been sought or given, but rather whether the sexual touching is deliberate/intentional.

The legal significance of sexsomnia is that it can provide an explanation for an otherwise unexplained sequence of events. In particular, sexsomnia can give rise to the legal defence of automatism.

The defence of automatism

An act carried out without control of the mind or whilst in a state of unconsciousness can be said to have taken place in a state of automatism. It is possible that this ‘automatism’ can be a legal defence because the involuntary movements that are performed do not ordinarily constitute the necessary physical actions required (‘actus reus’) to commit the offence. 

The defence of automatism can arise in a multitude of disparate situations where allegations are denied due to, for example, uncontrollable reflex actions, involuntary moments caused by a stroke or as a result of being attacked by a swarm of bees. Suffering from a sleep disruption such as sexsomnia is another example of behaviour which the law recognises can give rise to the defence of automatism. In order to support such a defence, medical evidence about sleep disorders is required.

Where the defence asserts sexsomnia, the burden is on the prosecution to prove beyond reasonable doubt that the defendant was not acting automatously. If the prosecution does not oppose the defence or fails to prove the defendant’s guilt beyond reasonable doubt, the defendant may be acquitted.

The defence of insane automatism

The defence of automatism cannot be relied upon if a criminal act was the result of a ‘disease of the mind’. There is currently a very fine and poorly defined line between circumstances that may cause non-insane automatism (as above) and insane automatism. 

The courts have held, for example, that non-insane automatism can include a situation where a diabetic person suffers an episode of hypoglycaemia (low blood sugar). On the other hand, historically, the courts have treated involuntary actions arising as a result of epileptic seizures as insane automatism due to the fact epilepsy is considered to be a ‘disease of the mind’. The distinction between the two seems to be somewhat arbitrary and has the potential to cause unfairness where the guilt of a defendant can be determined by the nature of the illness from which they suffer. The current provisions of insane and non-insane automatism are an area that is ripe for legal research and reform.

Parasomnia is not addressed in the Mental Health Act and therefore it is not formally considered to be a mental disorder. If it were to be classified as a disease of the mind, a defendant would be able to rely on the defence of insanity, on the basis that the individual was not responsible for their conduct at the time the act was committed. On conviction by reason of insanity, a judge can impose a hospital order, supervision order or absolute discharge.

Whilst some may feel uneasy about this defence which could lead to the acquittal of someone who has (unknowingly) committed an otherwise serious criminal act, it underlines the requirement for culpability. It is a fundamental principle of our criminal Justice System that those who suffer the misfortune of this and other similar conditions should not be convicted of an offence which is outside of their control.

Further information

For further information on the issues raised in this blog post, please contact a member of our criminal litigation team.


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