The phenomenon of sexual sadism was first scientifically described by Richard von Krafft-Ebing in 1999 as a sexual preference disorder that focuses on the infliction of suffering, pain, or humiliation to achieve sexual gratification. The present article reviews the historical development of the term sexual sadism, including the current descriptive nosology of psychiatric classification. Despite clear definitions that specify the sexual objects, duration, and distress necessary for a disorder, evidence for the diagnostic reliability for sexual sadism in the forensic domain is mixed. We argue that the reliance on the patient’s willingness to divulge corresponding violent sexual fantasies is the Achilles’ heel of the diagnosis. In an attempt to improve agreement across diagnosticians, we argue for the use of behavioral indicators. We summarize the extant research on the Severe Sexual Sadism Scale (SESAS), which is a file-based observer rating of pertinent crime-scene actions. We conclude that the analysis of crime-scene behavior, as achieved with the SESAS, can provide a useful complement for the clinical diagnosis in forensic psychiatry and psychology.