Philosophy, Psychiatry, & Psychology

Stephen Braude’s essay, “Multiple Personality and Moral Responsibility,” discusses a number of important issues about the moral and legal responsibility of persons diagnosed with multiple personality disorder (MPD), known in DSM-IV as Dissociative Identity Disorder (DID). One issue that is fundamental to this debate, which Braude does not address, however, is the empirical reality underlying the debate. Does MPD/DID exist? A prerequisite to a debate about the legal consequences of MPD/DID is legally sufficient proof of its existence and its behavioral consequences.

Proof that MPD/DID exists, its impact on legal standards of responsibility, and that the defendant suffers from it, must come from expert testimony; it is not part of the common knowledge or experience of the typical judge or juror. Courts are, however, increasingly, unwilling to assume that because an expert has impressive qualifications, he or she will necessarily present scientifically valid evidence. Particularly in cases of psychiatric and psychological evidence, courts that once looked solely at the expert’s qualifications to determine the admissibility for expert scientific evidence, now understand that the expert’s qualifications are a necessary but not a sufficient condition for the presentation of accurate expert testimony. Courts increasingly want to know how experts know what they claim to know and whether their methods of knowing meet the hallmarks of good science.

Thus, from a legal standpoint, a prerequisite to admissibility of the evidence that serves as a basis for a discussion of the legal implications of MPD/DID is rigorous scientific proof of its existence. Proof of the existence of MPD/DID has not, however, been the subject of rigorous scientific research, but instead has consisted of non-falsifiable clinical experience where the risk of iatrogenesis (i.e., hypnosis and suggestion) is ever present. While these clinical observations and opinions may ultimately be proven valid by subsequent research, there is simply no way to know whether that is so in the absence of rigorous scientific research. If proof of the existence of MPD/DID is clinically but not scientifically grounded, legal rules based upon it are suspect. Moreover, claims of MPD/DID often arise in a legal context where there are significant benefits to be gained from receiving the diagnosis which heightens the importance of rigorous scientific scrutiny.

Diagnostic validity and reliability matters in different ways in the forensic context than it does in the therapeutic context. These contextual differences [End Page 59] are reflected in disparate standards for scrutinizing each. There is no threshold requirement, for example, that a psychotherapist prove that a diagnostic category is valid or that a psychotherapeutic treatment used for a person suffering from it is generally recognized as safe and effective before using it; however, there is a threshold requirement of rigorous scientific scrutiny before admission of this information in evidence. If a therapist’s diagnostic hypothesis that there are two personality states influencing a patient’s behavior is not borne out, it can be revised in later sessions. Even if MPD/DID does not exist, treatment that assumes it does may nonetheless be effective because therapeutic outcome is more closely tied to the nature of the therapist-patient relationship than the content of therapy, or because multiple personality states is an effective therapeutic metaphor. Moreover, if the patient is not satisfied that the diagnosis or treatment rendered is helpful, the patient can leave therapy or seek another therapist.

In contrast, judicial determinations are a one-shot determination which cannot be revisited in light of subsequently acquired knowledge. The defendant/patient is not free to change courts, or withdraw from the legal proceedings. Thus, it would be entirely appropriate for psychiatrists and psychologists to treat patients presenting symptoms of what they label MPD/DID and for courts to reject exculpatory evidence from psychiatrists and psychologists of that disorder.