While there is no doubt that a life sentence is appropriate, such crimes always raise some doubt about the extent that psychopaths like Jutting have control over their actions. The idea that psychopaths have diminished responsibility because of genetic propensities is generally viewed with scepticism. Parents and education systems teach that we are solely responsible for our lot in life. Of course, intuitively, we are aware our genes have something to do with our behaviour. Just reading the news, we are aware that psychopathic behaviour is overwhelmingly associated with being male, one reason why there are far more men than women in prisons. So, biology obviously has an impact on criminal behaviour. Recent research findings are beginning to uncover more evidence that certain inborn biological markers are associated with criminality.

A man’s ring finger is more likely to be longer than his index finger, caused by differences in testosterone exposure levels in the womb. The more testosterone, the longer the ring finger. A growing body of research is now finding that the ring-index finger ratio is linked to male aggressiveness, impulsiveness and sensation seeking. And also that offenders in prison are more likely to have long ring fingers compared to index fingers than non-offenders, indicating an underlying genetic basis to criminality.