Sleep, Violence, and Forensic Implications

Abstract

Parasomnias are complex behaviors or experiences occurring out of or during sleep. Attempts at presenting parasomnias under the guise of the “Sleepwalking Defense” are increasing as potential explanations to account for violent behaviors in a broad range of criminal allegations ranging from assault and battery, to rape, and homicide. The sleep forensics expert must have a current understanding of neuroscience and somnology, sleep medicine with its clinical and diagnostic techniques, and the legal requirements of expert testimony pertaining to the presentation of scientific evidence. Historically, sleepwalking was understood upon a multitude of superstitious as well as religious-based constructs. It took until 1986 with the discovery of REM Sleep Behavior Disorder (RBD), a disorder in which individuals exhibit violent dream enactment behavior in REM sleep, which further strengthened the foundation that sleepwalking is predominantly due to aberrant neurophysiologic signaling in the brain though many discredited and pseudoscientific concepts continue to remain popular today. The development of a reasonable differential diagnosis for violent nocturnal behaviors, including NREM-related parasomnias (or Disorders of Arousal) and RBD, is not difficult as many present with characteristic clinical features. Sleepwalking and related disorders typically follow sudden partial awakenings from slow wave or deep sleep. Executive level functions and cognition are offline or severely limited and complex behaviors appear “automatic” in nature. Once abruptly aroused out of slow wave sleep, the sleepwalker may find themselves in an unstable state that has not yet been fully declared with a deactivated prefrontal cortex and midbrain structures that remain activated. It is upon this platform that overt behaviors may arise from sleep without awareness with more complex behaviors often taking on the appearance of reflexive primal expressions which may be violent, gustatory, or copulatory in nature. In any given episode of sleepwalking, violence may be possible though cases involving forensics implications are rare. In the vast majority of sleep-related violence with forensics implications, the victim was in relatively close proximity to the sleepwalker and may have inadvertently been the trigger for the event. Sleepwalking in adults occurs intermittently, and nocturnal wandering may not necessarily be sleepwalking. The sleep forensics expert understands that the strength of the argument in a court of law which associates any given Parasomnia with a criminal allegation ultimately rests upon effectively excluding other potential causes and cross contaminating influences (i.e., pharmaceutical effects) while providing a temporal association between a clinical condition and the degree of consciousness, or lack thereof, with the event in question. Thus, the role of the sleep forensics expert is much more than providing a clinical diagnosis and instead should, without bias, effectively facilitate the process in the courtroom to arrive at an educated decision.