Claims of Amnesia for Criminal Offenses: Psychopathology, Substance Abuse, and Malingering

Abstract

The forensic psychiatric examiner often encounters defendants who deny memory for their offense. Past research proposes a variety of factors to account for offense amnesia. To date there have been few systematic studies of offense amnesia in relation to psychiatric diagnosis, either alone or in combination with other known factors such as substance use and malingering. We studied 53 pretrial felony defendants who had been referred for psychiatric examination; 40% claimed amnesia for their offense. Examinees with psychotic disorders in general, and schizophrenia in particular, were relatively less likely to claim amnesia than were examinees with other diagnoses. Substance use at the time of the offense and associated substance use disorder diagnoses were positively associated with offense amnesia. Malingering diagnosed by general clinical criteria was a poor predictor of amnesia claims. These data suggests that two prominent reasons for referral for forensic psychiatric evaluation include the presence of psychotic symptoms and claims of amnesia for the offense.

Testing Claims of Crime-Related Amnesia

“…By and large, it seems that about 20 to 30% of those who have committed violent crimes claim crime-related amnesia ( 4 ). It should be noted here that this form of memory loss is not only reported by violent offenders: individuals convicted for sexual and property offenses also claim amnesia for their crimes ( 5 ).…”

“…Closed head injury, consumption of large quantities of alcohol, use of certain prescription or illegal drugs, low blood sugar (hypoglycemia), as well as shortage of oxygen (hypoxia) may result in a temporary deranged hippocampus ( 12 ). A considerable portion of offenders who claim crime-related amnesia report that their inability to recollect criminal events is due to alcohol consumption ( 5 , 13 ). However, drinking alcohol does not necessarily lead to amnesia.…”

Alleged amnesia in sexual crime

“…It is common to refer to amnesia of criminal acts in cases of extreme violence 13 or individuals who have consumed alcohol 3,14,15 . This is justified because alcohol intoxication causes alterations in the hippocampus that impair encoding memory and lead to a "blackout" 1 .…”

Tatbezogene Amnesien - authentisch oder vorgetäuscht?

“…Drittens werden bei Tatverdächtigen, die angeben, sich nicht an die Tat zu erinnern, häufiger neurologische und psychiatrische Untersuchungen durchgeführt als bei Personen, die keine Amnesie geltend machen [13]. Viertens kommen neurologische und psychiatrische Sachverständige in Fällen geltend gemachter tatbezogener Amnesien häufiger zum Schluss, dass die Tatverdächtigen an Substanzabhängigkeit, Depression oder einer anderen psychiatrischen Störung leiden als in Fällen ohne angegebene Erinnerungsprobleme [22,23]. Fünftens schließlich liegen Hinweise dafür vor, dass es einen Zusammenhang zwischen der Behauptung einer tatbezogenen Amnesie und der gerichtlichen Entscheidung gibt.…”

“…Auch Pyszora et al [13] berichteten, dass lediglich 15% der Verurteilten, die eine Amnesie geltend machten, in der Vergangenheit ein Schädel-Hirn-Trauma erlitten hatten oder an einer Epilepsie erkrankt waren. Auch in einer neuen Studie von Stout und Farooque [23] wiesen lediglich 15% der begutachteten Tatverdächtigen, die angaben, sich nicht an die Tat erinnern zu können, eine neurologische Anamnese auf. Ein anderes Beispiel stammt aus der Forschung über die Prävalenz von Schlafwandeln: Diese liegt in der Allgemeinbevölkerung bei ca.…”