Inside the brain of a SERIAL KILLER: Scientists study mass murderers to understand what lies behind their crimes

They are fascinating and terrifying in equal measure, but for many people understanding what motivates serial killers to murder many times over can be difficult to grasp.

Psychologists and neuroscientists are starting to build up a picture of the disturbing minds behind some of the most shocking crimes to have come to light in recent decades.

They have discovered surprising similarities between these mass murderers and have even found evidence that suggests a genetic abnormality that may act as a trigger.

While most people may be quick to dismiss serial killers as simply monsters, scientists are now attempting to understand what causes them to commit mass murder by studying their brains and their DNA. A new info graphic (pictured) has summarised some of the latest research on serial killers

Dr Helen Morrison, a forensic psychiatrist based in Chicago, has studied and interviewed 135 serial killers, according to an infographic compiled by the website Best Counseling Degrees.

She believes that in many cases the killers suffered a chromosome abnormality that led them to have an extra chromosome in their DNA.

For example, Bobby Joe Long, who is currently on death row in Florida for sexually assaulting and murdering at least 10 women in the Tampa Bay area, had an extra X Chromosome.

According to Dr Morrison this led to excessive amounts to oestrogen which began to cause him embarrassment and anger during puberty as he developed breasts.

Dr Helen Morrison studied and interviewed 135 serial killers and has found many of them share surprising similarities (illustrated). Perhaps most intriguingly she has identified chromosome abnormalities such as an extra X Chromosome or Y Chromosome during puberty may act as a trigger for their later behaviour 

Research has suggested many serial killers suffer a sense of detachment from the world around them that means they struggle to empathise with their victims. Professor Jim Fallon discovered that he himself had the brain of a psychopath (right in the picture above) which has dark patches on the orbital cortex behind the eyes

Researchers have also found psychopathic tendencies may be passed down through families and could be linked to a gene known as the Warrior gene, or MAO-A, which regulates the mood hormone serotonin in the brain (illustrated above). This may interact with brain activity and childhood experience

Similarly Richard Speck, who tortured, raped and murdered eight student nurses in Chicago, had an extra Y chromosome.

Dr Morrison has also said serial killers tend to develop a sense of detachment from the rest of the world from a very early age. This ultimately leads them to feel a lack of empathy for their victims.

Research by Professor Jim Fallon, a neuroscientist at the University of California, Irvine, has also been studying the brains of psychopaths using brain imaging.

He found low activity in the orbital cortex seems to be involved in sociopathic behaviours and have trouble suppressing rage and violence.

His work has shown that some people's brains appear to be predisposed towards violence.

Perhaps most surprisingly he found that his own brain scans show the same low orbital cortex activity as a serial killer. Scans of his son's brain showed normal orbital cortex activity.

The number of serial killers whose crimes are known about appears to have spiked during the 1980s but still remains disturbingly high, as the graph above illustrates

Serial killers like David Berkowitz (left), known as the Son of Sam, have been notoriously difficult to predict and so to catch, but new research may make it easier to identify them in the future. Bobby Joe Long (right) killed 10 women but was found to have an extra X Chromosome that scientists say could have been a trigger

Professor Fallon has also tested the DNA of his family for genes associated with violence and identified a gene known as the MAO-A gene.

Responsible for producing an enzyme called monoamine oxidase A, it is also known as the 'warrior gene' and regulates levels of the mood hormone serotonin in the brain.

Professor Fallon's discovery about his own brain led him to change his thinking about whether genes and brain function were the only pieces of the puzzle.

Serial killer Ted Bundy (pictured) was one of the most notorious in American history. He brutally murdered at least 30 women, confessing to the homicides shortly before being put to death in 1989

He now believes childhood experiences may also act as some sort of trigger that combines with these other factors to turn someone into a serial killer or a psychopath.

Writing in The Guardian, Professor Fallon said: '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?

'One most likely reason is that although I have the genetic makeup of a "born" psychopath, some of those very same "risk" genes in someone showered with love (versus abuse or abandonment), from childbirth through the critical first few years of life, appear to offset the psychopathy-inducing effects of the other "risk" genes.'

It is hoped that such research may make it easier to identify and catch serial killers in the future. 

Image source: www.bestcounselingdegrees.net