Article context: This research article examines the use of hypnosis in forensic settings, reviewing its history, applications in witness memory enhancement and investigative interviewing, the scientific evidence for its limitations, and the associated ethical and legal concerns.
Introduction
The application of hypnosis in forensic contexts has been one of the most controversial domains within both hypnosis research and legal practice. Proponents have historically argued that hypnosis could serve as a valuable investigative tool for enhancing the recollection of witnesses and victims — particularly in cases involving traumatic events where memory may be fragmented or suppressed. Critics, drawing on a substantial body of experimental research, have countered that hypnotically elicited memories are uniquely susceptible to distortion, confabulation, and the hardening of inaccurate beliefs, and that the use of hypnosis in legal proceedings poses an unacceptable risk to the integrity of evidence [1]. The debate has played out in courtrooms, legislatures, and professional guidelines across multiple jurisdictions, including Australia, the United States, and the United Kingdom. This article reviews the historical evolution of forensic hypnosis, the empirical evidence regarding memory effects, the current legal and professional frameworks governing its use, and the ethical considerations that continue to shape practice.
Historical Context
The use of hypnosis for forensic purposes dates to the mid-nineteenth century, when French neurologist Jean-Martin Charcot and his contemporaries explored the potential for hypnotic techniques to access memories presumed to be unavailable to ordinary consciousness [2]. The modern era of forensic hypnosis began in the 1970s, when law enforcement agencies in the United States — particularly the Los Angeles Police Department and the Federal Bureau of Investigation — began training investigators in “hypnotic interviewing” techniques. The 1976 Chowchilla bus kidnapping case in California brought forensic hypnosis to international attention. Under hypnosis, the bus driver was able to recall most of the licence plate number of the vehicle used by the kidnappers, contributing to the perpetrators’ identification and conviction [3]. This high-profile success fuelled enthusiasm for forensic hypnosis, and by the early 1980s, many US police departments had established formal forensic hypnosis programmes.
In Australia, forensic hypnosis was adopted more cautiously but has been used in select cases, particularly in New South Wales and Victoria, where trained police hypnotists have conducted investigative interviews with witnesses and victims. Notable Australian cases include the use of hypnotic interviewing in the investigation of the 1995 Walsh Street police shootings and several cold case homicide reviews [4]. However, the trajectory of forensic hypnosis globally has been one of increasing restriction, as the scientific evidence regarding memory contamination has accumulated and legal challenges to hypnotically enhanced testimony have succeeded.
The Scientific Evidence: Memory Effects of Hypnosis
The central scientific question underpinning the forensic hypnosis controversy concerns the effects of hypnotic procedures on memory. Early clinical reports suggested that hypnosis could produce vivid and detailed recall of previously inaccessible events, a phenomenon termed “hypermnesia.” However, controlled laboratory research has consistently demonstrated that while hypnosis may increase the total volume of information reported by a witness — including both accurate and inaccurate details — it does not reliably improve the accuracy of recall and may, in fact, increase the proportion of inaccurate information [5]. A seminal meta-analysis by Steblay and Bothwell (1994) synthesised data from seventeen experimental studies and found that hypnotic procedures produced a modest increase in correct recall (d = 0.32) but a substantially larger increase in incorrect recall (d = 0.54), resulting in a net decrease in overall memory accuracy [6].
The mechanisms underlying hypnotic memory distortion are well understood. The primary risk is that of suggestibility — the tendency for individuals in a hypnotic state to incorporate information embedded in the hypnotist’s suggestions into their memory reports, even when that information is inaccurate or leading [7]. This risk is compounded by confabulation, wherein the hypnotised individual produces richly detailed but fabricated recollections in response to the implicit demand characteristics of the hypnotic context. Critically, both the hypnotised individual and the legal fact-finder may be unable to distinguish between genuine memories and hypnotically suggested pseudo-memories, as both are experienced with equal subjective conviction [8]. A particularly troubling finding from the laboratory is that hypnotically induced false memories can persist over time and may be resistant to correction even when the individual is informed that the memory was suggested. This phenomenon, termed “memory hardening,” arises because the act of repeatedly retrieving a memory — even a false one — strengthens its subjective verisimilitude [9].
Legal Frameworks and Professional Guidelines
The legal status of hypnotically enhanced testimony varies substantially across jurisdictions. In the United States, the federal courts and a majority of state courts have adopted standards similar to those articulated in Rock v. Arkansas (1987), in which the U.S. Supreme Court held that a per se ban on hypnotically refreshed testimony is unconstitutional but that such testimony is subject to rigorous admissibility scrutiny [10]. Many states have enacted procedural safeguards, including requirements that hypnotic interviews be videotaped in their entirety, that the hypnotist not have prior knowledge of the case details (to minimise inadvertent cueing), and that only the witness and the hypnotist be present during the session.
In Australia, the approach has been more restrictive. The High Court of Australia has not directly ruled on the admissibility of hypnotically enhanced evidence, but appellate courts in New South Wales, Victoria, and Queensland have consistently held that such evidence is inadmissible where there is a significant risk of unreliability [11]. The Australian Law Reform Commission, in its review of evidence law, recommended that hypnotically induced testimony be excluded unless strict procedural safeguards have been observed and independent corroborating evidence exists. In practice, forensic hypnosis in Australia is now used almost exclusively as an investigative tool — to generate leads or lines of inquiry — rather than as a source of evidence to be presented at trial [12].
Professional guidelines from organisations including the Australian Society of Clinical Hypnotherapists, the International Society of Hypnosis, and the American Psychological Association uniformly caution against the use of hypnosis for memory recovery in forensic contexts. The guidelines emphasise that hypnotic procedures should never be used to “recover” memories in therapeutic settings where there is any prospect that those memories will become the subject of legal proceedings — a principle that has particular salience in the context of historical child sexual abuse allegations [13].
Ethical Concerns
The ethical dimensions of forensic hypnosis extend beyond the question of evidentiary reliability. A fundamental concern is the potential for harm to the witness or victim who undergoes a hypnotic interview. The induction of a hypnotic state in the context of a traumatic memory can precipitate abreactive phenomena — the intense and distressing re-experiencing of traumatic events — which may retraumatise the individual and exacerbate pre-existing psychological difficulties [14]. Unlike a therapeutic hypnotic session, in which the clinician has an ongoing duty of care and can provide follow-up support, a forensic hypnotic interview is conducted in the service of an investigation, and the welfare of the witness may be secondary to the investigative objective.
There is also the problem of investigator bias. Even where the hypnotist is independent of the investigative team, the framing of questions and the subtle cues inherent in the hypnotic interaction can convey the investigator’s expectations and hypotheses to the witness. The resulting memory contamination may distort not only the witness’s account but also the subsequent direction of the investigation, creating a cascade of downstream effects — misdirected investigative resources, confirmation bias in the interpretation of other evidence, and potentially wrongful arrest or conviction [15]. The risk is not merely theoretical; post-conviction DNA exonerations in the United States have identified cases in which hypnotically influenced witness testimony contributed to wrongful convictions, underscoring the gravity of the ethical stakes [16].
Conclusion
The forensic use of hypnosis sits at the intersection of psychology, law, and ethics in a manner that demands careful scrutiny. While the historical record contains instances in which hypnotic interviewing has generated productive investigative leads, the scientific evidence is unequivocal: hypnosis does not enhance memory accuracy, increases the risk of false memory formation, and produces effects that are resistant to correction. Contemporary professional guidelines and legal frameworks in Australia appropriately restrict the use of forensic hypnosis to investigative purposes only, with robust procedural safeguards. Future developments in the field may include the investigation of alternative interviewing techniques — such as cognitive interviewing and mindfulness-based approaches — that seek to enhance witness recall without the risks associated with hypnosis.
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