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Neuroscientist Jim Fallon (pictured above, with his family) has always been fascinated by the brains of psychopaths and has spent the last 20 years studying the brain scans and genetics of some of the world’s most prolific killers.

But when he underwent a brain scan and DNA test to assess his risk of developing Alzheimer's disease, he made the shocking discovery that he too had the biological make-up of a killer.

Like the killers he studied, part of his orbital cortex, the area of the brain which controls ethics and morality, was inactive. He also had several genes associated with aggression and violence.

Then his mother Jenny revealed at a family barbecue that seven of his paternal ancestors had been murderers.

They included a distant cousin, Lizzie Borden, whose story of murdering her parents is part of American folklore.

Jim spoke to Outlook's Lucy Ash from the University of California and told her why he has escaped becoming one of the murderers he studies.