The Monoamine Oxidase A (MAOA) Genetic Predisposition to Impulsive Violence: Is It Relevant to Criminal Trials?
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ORIGINAL PAPER
The Monoamine Oxidase A (MAOA) Genetic Predisposition to Impulsive Violence: Is It Relevant to Criminal Trials? Matthew L. Baum
Received: 17 August 2009 / Accepted: 4 April 2011 # Springer Science+Business Media B.V. 2011
Abstract In Italy, a judge reduced the sentence of a defendant by 1 year in response to evidence for a genetic predisposition to violence. The best characterized of these genetic differences, those in the monoamine oxidase A (MAOA), were cited as especially relevant. Several months previously in the USA, MAOA data contributed to a jury reducing charges from 1st degree murder (a capital offence) to voluntary manslaughter. Is there a rational basis for this type of use of MAOA evidence in criminal court? This paper will review in context recent work on the MAOA gene–environment interaction in predisposing individuals to violence and address the relevance of such findings to murder trials. Interestingly, the MAOA genetic variants impact future violence and aggression only when combined with the adverse environmental stimuli of childhood maltreatment. Thus nature and nurture interact to determine the individual’s risk. Based on current evidence, I argue there is a weak case for mitigation. But should future experiments confirm the hypothesis that individual M. L. Baum (*) The Ethox Centre, Division of Public Health and Primary Health Care, University of Oxford, Badenoch Building, Old Road Campus, Headington, Oxford OX3 7LF, UK e-mail: [email protected] M. L. Baum Oxford Centre for Neuroethics, University of Oxford, Littlegate House, Suite 8, 16/17 St Ebbes St, Oxford OX1 1PT, UK
differences in impulse control and response to provocation found in MAOA-L men (without abuse) are significantly magnified when combined with childhood maltreatment, the case could turn into a stronger one. Keywords Violence . Genetic predisposition . MAOA . Monoamine Oxidase A . Criminal responsibility . Neuroethics . Gene × environment interaction
Genetic Predispositions Enter the Courts On 18 September 2009, An Italian appeals court triggered controversy when it reduced the defendant’s sentence in response to evidence of a genetic predisposition towards violence [1–3]. In a brief editorial published in the European Journal of Human Genetics, Forzano et al. describe the murder case: “The convicted man [Abdelmalek Bayout] was an adult male affected by schizophrenia who […] was found guilty at the first level of judgement and was given a reduced sentence (9 years) owing to his mental illness. At the appeal court, a new expert assessment took place, and genetic testing was requested by the defence. […]The judge, however, reduced the sentence from 9 to 8 years, based on the fact that the accused had tested positive for genetic variants that made him particularly prone to be
M.L. Baum
aggressive under stressful circumstances and therefore he was even more vulnerable because of that.” [1]. The court found especially salient the expert testimony on the effect of Monoamine Oxidase A (MAOA)1 genetic va
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