The critical conditions for a sexual sadism crime are the suffering of the victim, intentionally elicited, and the sexual arousal of the offender by the suffering. Sexually sadistic behavior can include sadistic fantasy, sadism towards symbols, consenting or paid partners, and compliant victims. An investigator should be aware of certain behavior patterns such as sadistic personality disorder, cruelty during crime, pathological group behavior, sanctioned cruelty, revenge-motivated cruelty, interrogative cruelty, and postmortem mutilation which arise from different motives and contexts to avoid misinterpretation with sexually sadistic crimes. A study of 30 male, sexually sadistic criminals revealed that the offenders inflicted physical as well as psychological suffering on the victim. The offenders were more willing to talk about their violent acts than about their sexual acts or fantasies during interviews. In addition to sexual sadism, the offenders manifested other sexual deviations including homosexual activity and cross-dressing. The crimes were well-planned and carefully concealed; and the offenders retained incriminating evidence from these crimes including calendars, letters, photographs, videotapes, and media tapes. The investigator of a sexually sadistic crime needs uncommon insight, extensive knowledge, and sophisticated investigative resources. 3 footnotes