A case of a homicide and an attempted homicide during presumed sleepwalking is reported in which somnambulism was the legal defense and led to an acquittal. Other possible explanations including complex partial seizures, dissociative state, rapid eye movement sleep behavior disorder and volitional waking behavior are discussed. The evidence supporting the probability that this act occurred during an episode of somnambulism and sleep-related confusional arousal is reviewed and weighed. This evidence includes personal and family history of somnambulism and related disorders; neurological, psychiatric and psychological assessments; presence of possible precipitating factors; and polysomnographic data.