Behaviors that would otherwise be considered criminal acts, but occur in the context of a sleep disorder, pose challenges to the traditional application of legal principles of criminal responsibility. Determining the degree to which consciousness is present during such behaviors becomes a necessary step in assigning criminal culpability. Historically, legal defense theories of unconsciousness, automatism, and insanity have been raised to negate culpability for parasomnia related behaviors. Accordingly, proper assessment of sleep disorders in the context of criminal charges becomes critical in assisting the functions of the justice system. This article reviews principles related to the legal tradition, expert assessment, and elements of expert testimony related to criminal behaviors and sleep disorders.