Natural-Born Serial Killers: Do They Exist?

Can your genes make you snap? Ever since a Dutch woman pleaded with geneticists in 1978 to help her understand why there were so many brutally violent men born into her family going back until at least the 1870s, the question of whether our propensity for violence is in our genes has been a hot topic.

The Washington Post reports that the geneticists from University Hospital in Nijmegen, the Netherlands, found that they had mild developmental disabilities and their acts of arson, assault, attempted rape, and attempted murder may be attributed to these delays. It was only in the early 1990s that researchers were able to isolate a specific gene mutation that was common to all of the X chromosomes of all the violent male family members. Researchers noted that some of the women in the family had the same mutation but theorized that since women have two X chromosomes, the normal one would counteract the mutation on the other one.

The front cover of Popular Science this week asks, “Can your genes make you kill?”, acknowledging that it is an important but uncomfortable question because of its associations with eugenics and phrenology. It’s a question that needs to be answered for lawmakers as many turn to science to explain their defendant’s actions. In the case of Bradley Waldroup, the defense took the unprecedented step of sending Waldroup’s blood to be tested for a particular mutation that pre-disposed people to lack impulse control due to a build-up of seratonin and dopamine, leading them to snap. In Waldroup’s case, snapping meant shooting a woman eight times, cutting her head open with a knife, then chasing his wife with a machete and cutting off her pinky finger, and telling his children to “Come tell your mama goodbye,” before she miraculously escaped.

Waldroup was facing the death penalty, but when the lab came back with the results of his blood test showing that the MAO-A — the genetic variant on his X chromosome that coded the enzyme monoamine oxidase-A — was genetically present within him, jurors ruled out the death penalty and sentenced him to a hefty jail sentence.

It was the first time such evidence had been admitted, and it set a precedent for allowing that genetic mutations influence behavior, and it became known as the “warrior gene” defense.

National Geographic is airing a series tomorrow called The Story of God, and in the first episode titled “Understanding Evil,” they look at the work of Kent Kiehl, a neuroscientist who tells about his studies of the brain functions in psychopaths, where he maps prisoners’ responses to emotionally charged images and looks at where the activity lights up. In the minds of a psychopath, instead of lighting up the amygdala (fear response) and other emotional indicators, it lights up the logic section, presumably because the prisoner is trying to preempt what response would be considered normal.

“They have different brains,” Kiehl told Popular Science, and added that the variations he finds in the brain structures of psychopaths, including reduced gray matter and smaller amygdalas, are “at least 50 percent caused by genetics.”

“That shouldn’t surprise people with neuroscience knowledge.”

Genetics has already been implicated in alcoholism and anxiety, and violence may be added to that list.

The Daily Mail reports that a forensic psychiatrist based in Chicago, Dr. Helen Morrison, studied 135 serial killers and believes that in many cases the killers have an extra chromosome in their DNA that would lead to excessive amounts of oestrogen, causing embarrassment and anger during puberty, among other things.

The Mail cites the example of Bobby Joe Long, convicted murderer on death row for the murder of at least 10 women, who had this extra X chromosome.

[Image via Shutterstock]