Serial killers, so they say, are not all cross-eyed with a dodgy comb over and an Oedipus complex, but look like regular members of the public. Like you and I, apparently. But what is going on in their brain?
Obviously, if you have the urge to go out and slaughter people on a regular basis, there may be something wrong with the wiring of your brain. Technology, such as MRI scans, has enabled us to literally delve into the mind of psychopaths, which has allowed scientists to note that all is not as it should be in the brain of a serial killer.
So what is going on up there? A study conducted in 2013 by University of Pennsylvania professor of criminology Adrian Raine looked at neuro-imaging of violent criminals including murderers, psychopaths and serial killers to see how they are different to the everyday person.
It found diminished activity in areas of the brain are linked with self-awareness, the processing of emotions and sensitivity to violence. "The findings suggest that many people currently being punished for their crimes cannot actually control their behaviour, and should be seen as suffering from a disorder that needs treatment," said Raine.
Further research from Graeme Fairchild, a lecturer in clinical psychology at Southampton University, found adolescents with violent tendencies had a shrunken amygdala – the part of the brain that controls emotions and morality.
"People with severe forms of conduct disorder could be seen as having a brain development disorder, rather than just being evil," said Fairchild. "If the parts of your brain involved in feeling guilt or empathy are damaged, then there is an issue of diminished responsibility. It is too early to use this in the courts, but we have to ask if they are truly to blame for their behaviour."
An infographic from Best Counselling Degrees details why people turn to serial killing due to the abuse they suffer from an early age, which is defined as three or more kills in separate events, with a "cooling off" period in between. It says 18% of serial killers had been neglected, 26% sexually abused and 68% reported maltreatment in some form.