Boffins have found that cold-blooded killers have a shrunken amygdala, a brain defect linked to a lack of guilt and a higher risk of premeditated murder
Scientists have discovered a chilling brain abnormality that could unmask cold-blooded killers before they even strike. Experts scanning the minds of 37 accused murderers awaiting trial detected a critical, uniform defect deep inside the brain.
The tell-tale sign is a shrunken amygdala, the almond-shaped powerhouse responsible for regulating emotions, spotting danger and navigating moral choices. In convicted killers, this vital area was found to be nearly six per cent smaller than in other people.
Boffins now believe the high-tech brain scans can actually separate calculated executioners from those who simply snap in the heat of the moment. By examining case files and family histories to judge how much planning went into each atrocity, researchers made a jaw-dropping discovery.
The monsters who meticulously premeditated their crimes had an even more severely depleted amygdala, showing a massive 14.3 per cent reduction in volume.
Lead author Professor Adrian Raine, from the University of Pennsylvania, told the Daily Mail: “It’s the more ‘cold-blooded’ murderers who have blunted emotions as indicated by this impairment in the amygdala; an impairment that can contribute to a lack of concern for others.”
While previous studies have hunted for the “murder gene” in prison inmates, those results were always skewed.
Spending years behind bars in a brutal prison environment alters brain structure, masking any natural violent tendencies.
Professor Raine’s ground-breaking study bypassed this by scanning suspected killers in China undergoing psychiatric evaluation just weeks or months after their crimes – long before the prison system could warp their minds.
Using advanced structural MRI scans, the team mapped the killers’ brains and traced the exact boundaries of the amygdala.
They found the shrinking occurred specifically in zones tied to learning from fear and avoiding bad outcomes – areas often linked to aggressive behaviour. The study also revealed that these killers had a smaller lateral orbitofrontal cortex.
Professor Raine said: “Interestingly, other studies have shown that healthy controls show increased activation of this brain area when they accidentally kill an innocent victim in a video game, giving them a sense of guilt for their wrongful action.
“But if this brain area that gives rise to that sense of guilt is diminished, as it is in murderers, then that can take the brake off killing someone.”
Psychiatrists evaluating the suspects found that those with the smallest amygdalas scored the highest for psychopathic traits, particularly “emotional shallowness” and a total lack of remorse.
Alarmingly, even in ordinary, non-criminal citizens, a smaller amygdala correlated with higher psychopathic tendencies, predisposing them to violence. However, the team warns that a broken brain isn’t a guarantee of a killer lifestyle.
Professor Raine added: “Brain scans can help reveal abnormalities that are associated with an increase in the likelihood of committing crime, but prediction is not perfect. Some murderers have completely normal brain scans, and some normal people have abnormal brain scans.
“But in combination with social, psychological and health factors and the use of artificial intelligence and machine learning, prediction is likely to be improved in the future.”