Reduced sentence for murderer with 'genetic predisposition' to aggression

An Italian court has reduced the sentence of a convicted murderer by a year based on evidence that he carries genetic mutations linked to aggressive behaviour. This is the first time that genetics have been considered a mitigating factor in a European court sentencing.

In March 2007, Abdelmalek Bayout admitted to stabbing Walter Felipe Novoa Perez to death because he had insulted Bayout over the eye make-up he wore for religious reasons. At his trial, his mental illness was taken into account and he was sentenced to nine years and two months imprisonment - three years less than he would have received otherwise. At an appeal hearing in May this year, the judge requested a new psychiatric report. Two independent neuroscientists performed tests on Bayout. They found abnormalities in brain scans, and five gene mutations previously associated with aggression. Based on their report, the judge reduced the sentence by another year in September.

The judge said that he was particularly compelled by the presence of mutations in the gene encoding the enzyme monoamine oxidase A (MAOA), which influences the creation of particular chemicals (neurotransmitters) responsible for passing on signals between brain cells. Low levels of MAOA have been linked to delinquency and aggression in young boys raised in abusive environments. The report concludes that Bayout is genetically predisposed to aggressive behaviour when provoked.

However, expert scientists in this field have questioned whether the scientific findings really support these conclusions, Nature reports. Professor Nita Farahany of Vanderbilt University in the US, an expert on ethical issues related to behavioural genetics and neuroscience, argues that the behaviour of a single individual cannot be explained by their genes alone as behaviour is always strongly dependent on environmental factors - such as child abuse for aggression in people with low MAOA levels. 'The point is that behavioural genetics is not there yet, we cannot explain individual behaviour, only large population statistics', she says. Professor Terrie Moffitt of King's College London, UK, who contributed to the original research identifying the link between MAOA and aggression, claims that the results could be unreliable depending on Bayout's ethnicity, which was not tested.

Professor Steve Jones, a geneticist at University College London, raises a point of principle beyond scientific reliability: does a genetic predisposition ever diminish an individual's responsibility for their behaviour? '90 per cent of all murders are committed by people with aY chromosome - males. Should we always give males a shorter sentence?' he told Nature, adding 'I have low MAOA activity but I don't go around attacking people'.