REGULAR ARTICLE Amnesia and Crime Dominique Bourget, MD, and Laurie Whitehurst, PhD Amnesia for serious offenses has important legal implications, particularly regarding its relevance in the contexts of competency to stand trial and criminal responsibility. Forensic psychiatrists and other mental health profes- sionals are often required to provide expert testimony regarding amnesia in defendants. However, the diagnosis of amnesia presents a challenge, as claims of memory impairment may stem from organic disease, dissociative amnesia, amnesia due to a psychotic episode, or malingered amnesia. We review the theoretical, clinical, and legal perspectives on amnesia in relation to crime and present relevant cases that demonstrate several types of crime-related amnesia and their legal repercussions. Consideration of the presenting clinical features of crime- related amnesia may enable a fuller understanding of the different types of amnesia and assist clinicians in the medico-legal assessment and diagnosis of the claimed memory impairment. The development of a profile of aspects characteristic of crime-related amnesia would build toward establishing guidelines for the assessment of amnesia in legal contexts. J Am Acad Psychiatry Law 35:469–80, 2007 The forensic literature is replete with reports of of- classification of dissociative disorders. These incon- fenders who have claimed total or partial amnesia for sistencies have, in part, resulted in confusion sur- violent crimes, including murder or attempted mur- rounding how dissociation is conceptualized. Spitzer der.1–14 Claims of amnesia have been reported in an and colleagues21 reviewed recent efforts to clarify the estimated range of 10 to 70 percent of homicides. conceptualization of dissociation by distinguishing Memory impairment during the commission of between types (pathologic versus nonpathologic dis- crimes has also been reported by perpetrators of do- sociation) and related phenomena (detachment ver- mestic violence15–19 and by sex offenders.1–3,6 sus compartmentalization). Pathologic dissociation has been viewed as a categorical phenomenon char- Dissociation and Dissociative Amnesia acteristic of individuals with dissociative disorder,22 While memory disturbances are often associated while nonpathologic dissociation has been conceptu- with organic brain disease, crime-related amnesia alized as a dimensional construct that may range from common daydreaming to severe dissociative raises the question of dissociation, a term that refers 23–26 to the disruption of normally integrated functions of disorders. Although there is some empirical ev- idence of a distinction between pathologic and non- consciousness, memory, identity, or perception of 22,27 the environment. A dissociative state is an altered pathologic dissociation, there is ongoing contro- versy over its application to clinical diagnosis and state of consciousness concurrent with a traumatic 21 experience. Dissociative amnesia, formerly termed classification. psychogenic or functional amnesia, is a disorder Detachment is thought to arise from intense characterized by the inability to remember important fear or trauma and has been defined as an altered personal experiences and events after a traumatic ex- state of consciousness involving a disconnection 20 from one’s sense of self (depersonalization) or the perience of psychological origin. 28 Current psychiatric diagnostic systems differ in external world (derealization). Dissociative am- their definition of the term dissociation and in the nesia may result when detachment interferes with the encoding and storage of traumatic informa- 21,28,29 Dr. Bourget is Associate Professor, Department of Psychiatry, and tion. Compartmentalization is character- Part-time Professor, Department of Psychology, University of Ottawa, ized by the failure to control cognitive functions or and Forensic Psychiatrist, Royal Ottawa Mental Health Centre, Ot- tawa, Ontario, Canada. Dr. Whitehurst is Professor, Department of actions normally amenable to intentional control Psychology, University of Ottawa, Ottawa, Ontario, Canada. Address (including the inability to bring normally accessi- correspondence to: Dominique Bourget, MD, Royal Ottawa Mental 28 Health Centre, 1145 Carling Avenue, Ottawa, ON K1Z 7K4. E-mail: ble information into conscious awareness). The [email protected] affected functions and related information are pre- Volume 35, Number 4, 2007 469 Crime-Related Amnesia served and continue to influence emotion, cognition, stantially reduced glucose metabolism in the right and behavior. In this view, dissociative amnesia may frontotemporal area.45 Based on this research, represent the compartmentalization form of dissoci- Markowitsch47 suggested that the retrieval of auto- ation and reflect a retrieval deficit that prevents the biographical events is blocked or disrupted as a con- volitional recall of stored information. sequence of an imbalance in brain activity in patients with dissociative amnesia. In contrast, Yasuno et al.48 Theoretical Perspectives on Amnesia found increased activation in the right anterior medial temporal lobe (including the amygdala) in Dissociative Amnesia a patient with dissociative amnesia during a task Various frameworks have been put forth to ac- requiring explicit retrograde memory. In control count for how and why dissociative amnesia might subjects, bilateral hippocampal region activation occur. Many psychological explanations include the was increased during the task. During recovery proposal that dissociative amnesia serves a protective from the amnestic state one year later, the subject function of minimizing the adverse emotional con- showed decreased activation in the medial tempo- sequences of trauma, either by impairing encoding of ral region and increased activation in the right the traumatic experience,30 or by repressing the ex- 10,11 hippocampal region. perience from conscious awareness. Although Psychiatric accounts of crime-related dissociative repressed memory may be a plausible explanation for amnesia propose that a dissociative state due to dissociative amnesia, the lack of scientific evidence of 31 strong emotional stress is present during the commis- repression has been noted. sion of the offense. In this view, dissociation occurs Another explanation holds that dissociative amnesia and later memory retrieval is impaired by extreme is best understood from a biological and neurological levels of arousal accompanying crime-related behav- perspective.32 In this view, biological reactions to psy- chological trauma, such as neuroendocrine dysregula- ior. A heightened state of arousal may inhibit the encoding of an autobiographical memory for the tion resulting from extreme stress, have acute effects on 49 attention and memory encoding and consolida- event, or the person’s own actions may be the 30,32 source of the stress, impairing encoding and produc- tion. Repeated exposure to stress may result in 31,50 widespread alterations in neurotransmission33,34 and ing the amnesia. However, the premise that dis- direct effects on brain function.32,35 sociative amnesia stems from concurrent high emo- Studies of glucocorticoid treatment in humans tional stress has been questioned, based mainly on have shown that elevated glucocorticoid levels re- the argument that amnesia does not always develop duce traumatic memory retrieval36–40 by inhibit- for events that are accompanied by strong emotional ing activity in the medial temporal lobe.37 Acute reactions.51 psychosocial stress may impair delayed memory 41 41 retrieval in humans. Kuhlmann and colleagues Amnesia Due to a Psychotic Episode suggest that retrieval of emotionally arousing ma- Crime-related amnesia may occur due to the pres- terial is particularly sensitive to the effect of psy- chosocial stress. ence of a psychotic episode. Psychosis is associated It has been noted that the distinction between or- with an increased prevalence of violent crime, includ- ing homicidal behavior.52–59 Taylor and Kopel- ganic amnesia and dissociative amnesia may be arbi- 14 trary, as both may be a consequence of brain changes man reported that 7 of 19 offenders who claimed that lead to disruptions of memory processes. amnesia for their violent crimes had a primary diag- Markowitsch and colleagues42–46 described several nosis of schizophrenia. A recent study of the psychi- patients with dissociative amnesia who, compared atric aspects of 118 cases of criminal homicide found with nonamnesic patients, showed metabolic brain that psychotic disorder, mainly paranoid schizophre- alterations in memory-processing regions. In one pa- nia, and alcohol intoxication accounted for the of- tient, positron emission tomography (PET) imaging fenses of 24 percent of offenders who claimed amne- did not show increased right-hemispheric glucose sia for their crimes.60 It has been suggested that the metabolism during a task requiring autobiographical presence of psychosis impairs attention, impeding memory,42 whereas another patient displayed sub- the encoding of events.2,9 470 The Journal of the American Academy of Psychiatry and the Law Bourget and Whitehurst Amnesia Due to Sleep Disorders Conversely, Wolf77 showed that when a significant Amnesia for crime may also be associated with amount of alcohol was given to homicide offenders sleep disorders. There are several case reports of am- claiming amnesia for crimes committed under the nesia for violence, including homicide, committed in influence of alcohol, the offenders