A serial killer is traditionally defined as a person who murders three or more persons, in at least three separate events, with a ‘cooling off’ period in between. Think of some of the most famous serial killers in history – The Zodiac Killer, Ted Bundy, Jack the Ripper, the .44 Caliber killer or The Co-Ed Killer – these violent criminals seem to share little in common with each other except for the depraved need to kill many times over and a deeply disturbing lack of empathy. Each serial killer has a distinct MO, motive and  choice of victim, and so, for a long time, scientists have struggled with trying to understand what goes into the making of a serial killer.

Dr. Helen Morrison’s Recent Discovery About Chromosome Abnormalities in a Serial Killer 

However, the findings of Dr. Helen Morrison may change that. A forensic scientist based in Chicago, Morrison has interviewed and studied 135 serial killers and believe that they share startling similarities. The most important of her findings is that a chromosome abnormality, such as an extra X or Y chromosome in their DNA, might act as a possible trigger for their murderous behavior. To explain this, Morrison used the example of Bobby Joe Long. Long, who is currently on death row in Florida for the sexual assault and murder of at least 10 women in the Tampa Bay area, had an extra X chromosome in his DNA. Consequently, there was an increase in the level of estrogen in his body. As Long developed breasts and started noticing unfamiliar changes in his body during puberty, it is possible that he harbored feelings of anger, resentment and embarrassment.

Morrison also identified another key developmental factor – a sense of detachment from the rest of the world at a very early age. This means that they lack any feelings of empathy and, in the absence of empathy, they find themselves being able to ‘experiment’ on their victims and, ultimately, kill them.

Professor Jim Fallon’s Study of the Mind of a Serial Killer

1 Low Activity in Brain’s Orbital Cortex

Professor Jim Fallon, a neuroscientist at the University of California, Irvine, has been using brain imaging to study some ofthe most twisted minds in history. The orbital cortex of the brain is that area which is associated with ethical behavior, moral decision-making and impulse control. Fallon’s most important finding was that a low level of activity in the brain’s orbital cortex is found in those with sociopathic tendencies, making it difficult for them to suppress impulses of rage, violence, hunger or sexual desire. Therefore, his work shows that some people’s brains are naturally predisposed to violence. Perhaps what was most disturbing for Fallon was discovering that his brain showed the same low orbital cortex activity as a serial killer. His son’s brain scans, however, were normal.

2 The MAO-A or Warrior Gene

Fallon also tested the DNA of his family for genes associated with violence. This led to his discovery of the MAO-A gene i.e. a gene that produces the monoamine oxidase A enzyme. The MAO-A gene is also known as the ‘warrior gene’ and regulates levels of the mood hormone, serotonin, in the brain.

3 A history of abuse

Puzzled by his brain scans, Professor Fallon could not understand how he had escaped his genetic destiny of being a serial killer. “Why, in the light of the fact I have all of the biological markers for psychopathy, including a turned off limbic system, the high risk genetic alleles, and the attendant behaviours, including well over half of those listed in the psychopathy tests and low emotional empathy, did I turn out to be a successful professor and family man?”, he wrote in The Guardian.

Fallon concluded that serial killers, most likely, experience a trigger – such as a traumatic childhood event or abuse – which combines with other genetic factors and makes them act on their dangerous, violent impulses.

The findings of both these scientists have been illustrated as an infographic by Best Counseling Degrees and can be accessed here.

Hopefully, these insights will make it easier to understand, identify, arrest and convict serial killers in the future.