Sexsomnia and criminal responsibility: A forensic case report

Introduction Sexsomnia is a non–rapid eye movement parasomnia characterised by complex sexual behaviours arising during incomplete arousals. Forensic interpretation remains challenging because of diagnostic uncertainty and the limitations of retrospective attribution. This case contributes to the limited literature on sexsomnia in forensic contexts involving allegations of sexual misconduct. Case presentation Case presentation: A 33-year-old man underwent forensic neuropsychiatric evaluation following alleged nocturnal sexual contact with his 9-year-old daughter. A history of lifelong confusional arousals, recurrent amnestic sexual behaviours in adulthood, severe obesity, untreated obstructive sleep apnoea (apnoea–hypopnoea index 14.6 events/h), and modest alcohol consumption prior to the index event (two 33-cL beers) was reported, with complete amnesia for the episode. Neurological examination, brain magnetic resonance imaging, and laboratory investigations were unremarkable. Diagnosis, interventions, and outcomes ultidisciplinary forensic assessment considered alternative explanations inluding nocturnal epilepsy, REM sleep behaviour disorder, dissociative states, substance-induced behaviours, and malingering-and judged them unlikely on clinical grounds. The findings were considered consistent with a disorder of arousal presenting with sleep-related abnormal sexual behaviours (sexsomnia). Conclusion In the presented case, the behaviour was considered consistent with sleep-related automatism, and the subject was deemed not criminally responsible for the alleged act. While automatised behaviours may plausibly occur during dissociated sleep–wake states, forensic attribution remains inherently limited. Legal accountability cannot be inferred from clinical diagnosis alone but requires integration of longitudinal clinical coherence with evaluation of consciousness, volitional control, foreseeability, and risk-mitigating measures. In the absence of standardised forensic criteria, methodologically rigorous multidisciplinary assessment remains essential.