Formerly called multiple personality disorder, dissociative identity disorder (DID) is a controversial diagnosis that challenges forensic psychiatrists, other mental health clinicians, legal professionals, the media, and the public. DID cases often present in the criminal justice system rather than in the mental health system, and the illness perplexes experts in both professions.
Individuals may commit criminal acts while in a dissociated state. A study that tracked 21 reported DID cases found that 47% of men and 35% of women reported engaging in criminal activity, including 19% of men and 7% of women who committed homicide.1 Defendants occasionally use DID as a basis for pleading not guilty by reason of insanity (NGRI). Controversy over the DID diagnosis has contributed to debates about the disorder’s role in criminal responsibility.
The DID diagnosis
An American Psychiatric Association Work Group has proposed new diagnostic criteria for DID for DSM-5, which is scheduled to be published in May 2013.2 Presently, DID is listed in DSM-IV-TR as an axis I disorder.3 Criteria for DID include the presence of ≥2 distinctive identities or personality states that recurrently take control of an individual’s behavior (Table 1).3 This is accompanied by an inability to recall important personal information to an extent that cannot be explained by ordinary forgetfulness. Patients with DID typically have a primary identity that is passive, dependent, guilty, and depressed, and alternate identities with characteristics that differ from the primary identity, commonly in reported age and gender, vocabulary, general knowledge, or predominant affect.3
Dissociative pathology may result from trauma, comorbid mental illness, or other medical issues, including complex partial seizures. Developmental theorists have proposed that severe sexual, physical, or psychological trauma in childhood predisposes an individual to develop DID.4 Theoretically, harm by a trusted caregiver forces a child to split off awareness and memory of the trauma to survive in the relationship. Later these memories and feelings are experienced as a separate personality. Because this process happens repeatedly, the patient develops multiple personalities; each has different memories and performs different functions, which may be helpful or destructive. Later, dissociation becomes a coping mechanism when individuals face stressful situations.5
Personality traits that may predispose patients to develop a dissociative disorder include mental absorption, suggestibility, ability to be easily hypnotized, and tendency to fantasize.6 Patients with dissociation also may meet criteria for posttraumatic stress disorder, borderline personality disorder, somatoform disorder, eating disorder, or substance use disorders.7
Table 1
DSM-IV-TR criteria for dissociative identity disorder
| The presence of ≥2 distinct identities or personality states, each with its own relatively enduring pattern of perceiving, relating to, and thinking about the environment and self |
| At least 2 of these identities or personality states must recurrently take control of the person’s behavior |
| An inability to recall important personal information that is too extensive to be explained by ordinary forgetfulness |
| The disturbance is not due to the direct physiological effects of substance or a general medical condition. In children, the symptoms are not attributable to imaginary playmates or other fantasy play |
| Source: Reference 3 |
DID and NGRI
An insanity defense is raised in <1% of felony cases, and is successful in only a fraction of those.8 A criminal defendant who claims NGRI asserts that he committed the offense and asks the court to find him not culpable because of his mental state when the offense occurred.
The legal approach used by the defense in cases of NGRI due to DID will be determined by the jurisdiction in which the case is tried. The “Alter-in-control” approach considers the key issue as which “alter” (personality) was in control at the time of the offense and whether he or she met the insanity standard, the “Each-alter” approach considers whether each personality met the insanity standard, and the “Host-alter” approach considers whether the dominant or primary personality met the insanity standard.9
Legal and mental health professionals are divided on whether DID warrants an acquittal for insanity. The first time DID was recognized as a mental disorder that could excuse criminal responsibility occurred in State v Milligan (1978).10 The court declared serial rapist Billy Milligan insane due to lack of one integrated personality and therefore not culpable of the crimes he committed. Public outrage was extraordinary. Since this case, most DID defenses have not been successful (Table 2).10-16