The use of hypnosis in the field of forensic medicine causes a controversy compounded by serious misconceptions about hypnosis itself. Hypnosis is not sleep; it is, rather, a state of alert, attentive, receptive, integrated concentration characterized by a parallel awareness. The least controversial use of hypnosis is to enhance memory enough to recall simple, circumscribed data; a more dramatic use of hypnosis is the uncovering of amnesic periods. A series of case illustrations--the Reilly case, U.S. v. Thornton, among others--emphasize the Janus-like quality of data obtained through hypnosis. This feature enables extremely accurate revivification and recall of perceived events, but can also evoke false memories, false confessions, and the 'honest liar syndrome.' All data obtained under hypnosis are vulnerable to the counterclaim of memory contamination or coercion (innocent or designed). It is thus imperative to document all prehypnosis data as separate and distinct from information obtained during and after hypnotic interrogation. Although it is easy to identify information elicited under formal trance interrogation, it is not so easy to identify posthypnotic influences in testimony after the hypnotic interrogation has occurred and to determine to what extent perspectives and facts are contaminated by the interrogation. The best defense against the innocent or calculated abuse of hypnosis is for every person engaged in the interrogation process to become sensitive to the subtle signs of emerging spontaneous trance in the subject being questioned. The assessment of hypnotic capacity by means of the Hypnotic Induction Profile (HIP), a 5-to 10-minute clinical test, can also offer a presumptive indication of relative mental health or illness as well as personality style. This, in turn, yields information about which pathological syndrome is most likely to occur in that particular person under stress. Ten references are provided.