The use of hypnosis to enhance the memory of a witness to a crime often results not only in some additional accurate recall of information about the event but also in the incorporation of additional misinformation into the witness’s memory of the event and a general increase in his or her confidence in the veracity of recall. Research has shown that hypnosis increases the amount of information that is recalled about an event. This effect often occurs with other techniques also, such as the cognitive interview. When techniques such as hypnosis and the cognitive interview are used to enhance a witness’s memory, the amount of new information recalled turns out to be a mixture of accurate and inaccurate information. Furthermore, once accurate and inaccurate information get mixed into a coherent narrative, the witness is typically not very good at distinguishing those aspects of the story that are true from those that are false. The additional information will make the narrative the witness is trying to construct more coherent, and his or her confidence in it will increase. The witness’s memory has not been refreshed. A more coherent narrative has been constructed that the witness feels is a more accurate representation of the event he or she is being encouraged to remember.
Admissibility of Hypnotically Refreshed Testimony
The problems associated with hypnotically refreshed testimony have been recognized in hundreds of decisions by American courts. In 1987, the U.S. Supreme Court considered the admissibility of hypnotically refreshed testimony in Rock v. Arkansas. Following the per se exclusionary rule, the trial judge in this case determined that the hypnotically refreshed memories of the defendant were inadmissible. There was a growing trend in state courts at the time toward total exclusion of hypnotically refreshed testimony. In Rock v. Arkansas, the Supreme Court acknowledged that the possibility for contamination of the witness’s memory increases significantly when attempts are made to hypnotically refresh the witness’s memory; however, the court determined that the per se exclusionary rule cannot be applied if in doing so a defendant is denied his or her constitutional right to testify. State courts that have to deal with this kind of testimony generally recognize the problems associated with it and often apply the per se exclusionary rule to the hypnotically refreshed testimony of wit-nesses other than the defendant. Those courts that do not follow the per se exclusionary rule are usually willing to allow hypnotically refreshed testimony only if certain safeguards have been adhered to in the conduct of the hypnotic interview.
Theories of Hypnosis
A number of different theories have been proposed regarding the nature of the hypnotic experience and its relation to the behavior of the hypnotized subject. There are several characteristics of the hypnotic state that distinguish it from the normal waking state. Ernest Hilgard has proposed the following list: increased suggestibility, enhanced imagery and imagination, subsidence of the planning function, and reduction in reality testing. Hilgard contends that hypnotic phenomena often reflect a split in consciousness. It appears that the experience of the hypnotized subject is dissociated from the subsystems of control that are regulating the subject’s perceptions and behavior. The major alternative to this point of view is sociocognitive theory. The emphasis in sociocognitive theory is on the social psychological relationship between the hypnotist and the subject. According to this theory, there is no need to propose that the subject has entered into some kind of trance state or that some kind of split in consciousness has occurred;
the hypnotized subject is engaged in the performance of a role in a social situation that is largely under the control of the hypnotist. Hilgard acknowledges the fundamental importance of the social psychological aspect of hypnotic phenomena, but he contends that changes in consciousness occur when a subject is hypnotized that cannot be accounted for by efforts on the part of a compliant subject to please the hypnotist. In their theory of dissociated control, Erik Woody and Kenneth Bowers propose that hypnotized subjects are in a state temporarily like that of patients with frontal lobe damage. According to their theory, the perceptions and behavior of the hypnotized subject are under the regulation of lower-level subconscious systems that are not being monitored by the frontal lobe executive.
If hypnotized subjects process information primarily at a subconscious level, then the kinds of rules that are applied in the evaluation of information by hypnotized subjects are likely to be very different from those applied in the conscious rational analysis of information. Seymour Epstein has provided considerable support for the idea that much of the information processing that occurs in our everyday lives consists of rapid evaluations of environmental stimuli that depend largely on subconscious schemata associated with emotionally significant past events. What we might have with hypnosis is an exaggeration of this aspect of normal experience. If the subconscious experiential system dominates information processing during hypnosis, then what may occur is not that missing material gets dragged up from the unconscious to fill in the gaps in memory but that the gaps in memory are filled in with plausible information that is suggested either directly or indirectly during the hypnotic interview. It turns out that hypnosis tends to produce this kind of effect whenever the subject is required to produce a narrative reconstruction of a highly emotional event. In studies that employ stimuli of low emotional impact, hypnosis does not produce an increase in the amount of information recalled. Furthermore, it is with free recall that we see the effect of hypnosis on the amount of information recalled; when specific questions are asked or when the subject is asked to decide between various alternatives, responses are restricted so that the tendency to produce more is not revealed.