Somnambulism or sleepwalking is a viable defence on the basis of automatism. The behaviours that occur during sleepwalking can be highly complex and include sexual behaviour of all types. Somnambulistic sexual behaviour (also called sexsomnia, sleep sex) is considered a variant of sleepwalking disorder as the overwhelming majority of people with Sexsomnia have a history of parasomnia and a family history of sleepwalking. Sexual behaviour during a sleep automatism can vary from explicit sexual vocalisations, to violent masturbation, to complex sexual acts including anal, oral and vaginal penetration. A recent case in England is reported where the defendant was acquitted on 3 charges of rape on the basis of automatism due to somnambulistic sexual behaviour.
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