For a number of years, scientists have studied brain and genetic abnormalities alongside crime. This work has produced some exciting findings, and some which have been used to argue for leniency in the justice system. We now know that certain genetic variations, such as monoamine oxidase, are linked to violent behaviour. The question is can your brain make you commit crime?

The short answer is no. It is important to remember that correlation and causation are not the same thing. If every violent criminal had a particular brain abnormality, you’d have 100 percent linkage between the behaviour and this brain variant, and the correlation would certainly be worth investigating. It still wouldn’t be causation unless this abnormality was never present in non-violent people too.

Despite this, the findings of neurological science are increasingly being used in the American justice system. Nita Farahany, a professor of law and philosophy at Duke University, studied over 10,000 court cases and found that more and more lawyers are using the findings of neuroscience and behavioural genetics to explain behaviour. This is troubling. First off, how neurobiology affects behaviour is as simple as X causes Y; secondly, a great number of neuroscientific studies were used in ways well outside accepted academic or scientific parameters.

Although neurological factors certainly do prompt certain behaviours, Farahany found that neurobiological findings are not likely to be accepted by the courts as evidence of guilt or innocence. The justice system works on the assumption that all behaviour, criminal or not, is the result of voluntary and self-directed action. Claiming you killed someone in a bar fight because you’d bumped your head a few days earlier is unlikely to get anyone off.

One way it has been used was to claim a defendant was incompetent to stand trail; a second is as an argument that a defendant was not competent to confess or understand his or her rights. Another way neuroscience has been used is to make claims for lenient sentencing or on appeal, such as by claiming that defence lawyers failed to amount an effective defence because they didn’t investigate a client’s neurobiology. So far the courts have not been swayed — in 70 to 80 percent of cases where this was used, defendants were unsuccessful upon appeal.

This is probably a relief to scientists whose work has been used in ways never intended and not warranted. Neurobiology is an excellent tool for explaining the behaviour of people — but not the individual person. Yes, our brains may cause us to be more likely to do one thing instead of another, but human beings, and neuroscience, are far more complex than that.