Dissociative Identity Disorder: Medicolegal Challenges

Causes and Pathology

Today, it is generally agreed that a required antecedent of dissociation is a traumatic event.⁷ Theoretically, harm by a trusted caregiver forces one to split off awareness and memory of the trauma to survive the relationship. These memories and feelings recede into the subconscious and emerge later in the form of a separate personality. This process happens repeatedly at different times, so that different personalities develop, containing different memories and performing different functions that are helpful or destructive. Later, dissociation becomes a coping mechanism for individuals when faced with further stressful situations.⁸

Constitutional predisposition for development of a dissociative disorder includes personality traits, such as being easily hypnotized, mental absorption, suggestibility, and a tendency to fantasize.⁹ Co-morbidities with dissociation include posttraumatic stress, borderline personality, somatoform, and eating and substance-abuse disorders.¹⁰

DID may also result from co-morbid mental illness or other medical conditions, including complex partial seizures. While it is beyond the scope of this article to provide an in-depth review of neuropsychological and neuroanatomical studies of personality and memory, advances in neuroimaging techniques serve to remind us that much remains to be learned in the area of neurobiology.⁹

Dissociative pathology, despite the renaming of multiple personality disorder (MPD) to DID, remains an Axis I disorder in the DSM-IV-TR.¹¹ Although the American Psychiatric Association Work Group has proposed new diagnostic criteria for DSM-5, scheduled to be published in May 2013,¹² its current criteria are listed in Table 1. The purpose of the DSM-IV-TR is to provide clear descriptions of diagnostic categories to enable clinicians and investigators to diagnose, communicate about, study, and treat people with various mental disorders.¹³

NGRI and DID

Utilization of the DSM, however, becomes challenging in legal situations. The DSM influences, but does not control, the definition of mental disorder in the test of criminal responsibility.¹⁴ Ultimately, the judge or jury decides whether the accused has proven that he suffered from a mental disorder that meets the statutory requirement(s), often including inability to appreciate the nature and quality of the action in question.¹⁵

In cases of NGRI with multiple personalities, the astute defense attorney will utilize one of three legal approaches.¹⁶ The alter-in-control approach, which is the prevailing defense, considers the key question to be what alter (personality) was in control at the time of the offense and whether the alter meets the insanity standard. The each-alter approach considers whether each personality meets the insanity standard. Finally, the host-alter approach considers the key issue to be whether the dominant or primary personality meets the insanity standard.

The dissociative state has emerged as an important consideration in numerous legal cases.¹⁷ Legal and mental health commentators are divided about whether dissociative disorder warrants an acquittal for insanity. Complexities arise when evidence of a dissociative state or dissociative amnesia is offered in court. One such complexity concerns how each phenomenon relates to personal control over behavior. Arguments have been made for excusing those with DID from responsibility. Some experts believe that a person with DID is a single person in the grip of a very serious mental disorder and that such a person is unable to fulfill the ordinary conditions of responsible agency (autonomy and self-control).¹⁸

In support of DID's being exculpatory, an argument can be made that since courts have acquitted defendants who show evidence of automatism, a dissociative state,^19,–,21 the same should be the case for DID. The Canadian case R v. Stone,²² conversely, held that exculpation hinges on whether criminal behavior is involuntary, regardless of the state of consciousness.²³

The recognition of MPD as a mental illness that would excuse criminal responsibility did not occur until Billy Milligan was declared insane in 1978 (State v. Milligan).²⁴ In that case, the argument for application of the insanity defense to the case of DID was that the defendant did not have an integrated personality. Rather, coexisting within the same individual were both criminally responsible and nonresponsible personalities. Public outrage was extraordinary, given that this serial rapist was not held culpable, and afterward, most DID defenses did not hold up, as shown in Table 2. For example, in a 1980 case in Oregon,²⁵ a defendant charged with murder pleaded insanity due to multiple personalities. The appellate court found that having multiple personalities does not automatically preclude having responsibility for the murder and that the question of criminal responsibility was properly referred to the jury (as opposed to a directed verdict for the defense).

The defense used in State v. Grimsley²⁶ was insanity due to multiple personalities. The court ruled that it was immaterial what state of consciousness or personality the defendant was in as long as the personality controlling the behavior was conscious and aware of his actions. The defense in Kirkland v. State²⁷ also asserted an insanity defense based on a psychogenic fugue. The court found that the law adjudges criminal liability of the person according to the person's state of mind at the time of the act, and the law will not inquire whether the individual possesses other personalities, fugues, or even moods in which he would not have performed the act. State v. Jones²⁸ found William Jones guilty of murdering a woman he met at a bar, despite expert testimony that his multiple personalities “paralyzed” him and hindered from knowing right from wrong.

More recently, courts have rejected the admissibility of DID evidence, including expert testimony, because the scientific evidence fails to meet reliability standards and therefore is not ultimately useful to the judge or jury. In State v. Greene,²⁹ the defendant claimed that 1 of his 24 alters was responsible for killing his therapist. The Supreme Court of Washington affirmed that evidence of Mr. Greene's DID, including expert testimony, was not reliable and not admissible.

Similarly, in State v. Lockhart,³⁰ Mr. Lockhart contested his conviction of first-degree sexual assault on the basis that he was not permitted to present evidence of DID to support his insanity defense. The West Virginia Court held that the diagnosis of DID was speculative and therefore did not meet reliability standards of evidence.

DID and the Forensic Expert

Admission of expert testimony into court regarding DID is an ongoing debate that involves forensic psychiatrists.³¹ While some courts have allowed testimony on dissociative disorders, others have denied the validity of dissociations or acknowledged the lack of scientific information available on the diagnosis. Evidence of dissociation in accused persons during acts of severe violence is highly problematic because of the legal significance of dissociative symptoms.³²

When a report of dissociation emerges in a criminal case, the stakes are high. A major consideration is the possibility of malingering alter personalities to evade responsibility. If malingered symptoms were mistakenly viewed as valid evidence of a dissociative state (a false-positive error), the court could unjustly adjudicate the defendant NGRI.

The accurate determination of the credibility of symptoms in defendants is difficult because the primary source of information is self-report.³³ There are motivations for malingered alters in criminal offenders. Feigned symptoms may serve to support a legal defense of NGRI to elicit sympathy, to raise doubt about the person's involvement in the crime, or to avoid using the much more risky and cognitively taxing approach of explicit deception.³⁴ A motivation to malinger in psychopathic offenders may simply be pathological lying or even “duping delight.”³⁵

In a medicolegal context, forensic experts who are asked to evaluate such a claim, should conduct a thorough investigation using multiple hypotheses and techniques.³⁶ While DSM-IV-TR criteria are a useful tool, all relevant information, including clinical history and assessment, collateral information, and past and present behavior should be considered in a primary diagnosis. Experts must be suspicious of malingered alter personalities that manifest as exaggerated details of alter states.³⁷

Historically, specific techniques used to evaluate a report of DID have included polygraph and symptom suggestion. The polygraph depends on the assumption that a person will show an emotional or physiological response when being deceptive, reflecting a fear of detection or guilt about lying.³⁸ However, the polygraph is prone to false-positive errors and can also be fooled by means of countermeasures such as drugs or mental imagery.³⁹

Experts now must use a multidisciplinary and multitechnique approach. An evaluation of the individual's verbal and nonverbal behaviors that could indicate malingering should be undertaken during interviews regarding the event in question. Self-report questionnaires such as the Structured Inventory of Malingered Symptomatology⁴⁰ can be used to evaluate the tendency to exaggerate memory complaints (indicative of malingering). The Dissociative Experiences Scale⁴¹ can be employed as a screening instrument for dissociative symptoms, and structured interviews such as the Dissociative Disorders Interview Schedule⁴² can be used to assess whether the individual has a dissociative disorder.

It is important to recognize that converging evidence indicates that dissociative amnesia in defendants is authentic in some cases, despite the general skepticism from legal decision makers. Further, it can be concluded that dissociation is malingered in some cases, causing a significant challenge in medicolegal contexts.