In your own opinion, what biological, psychological, and/or sociological elements account for a serial killer's behavior or actions across cultures?

There is enough research on the topic of serial killers to establish a very informed opinion about the issue. It is the question of nature vs. nurture. Does the killer's action reflect a biological factor at play or is it the social environment in which the subject is raised that makes them behave the way the do.

The study of serial killers has netted a number of biological issues at play. First, the brain of psychopaths and sociopaths does not function properly. Through brain scans, a malfunction of the low orbital cortex has been identified in killers. This is the area of the brain that it responsible for impulse control and the ability to regulate morality and ethics. Killers have brains that show low or no levels of activity in that part of the brain. Dr. Helen Morrison has also discovered a chromosome abnormality in serial killers that may act as a trigger. There has been evidence of killers having an extra x or y chromosome, but the study of this area is in its infancy. Most experts feel that these factors are only predispositions and do not guarantee that somebody will end up killing.

A number of psychological disorders are identified in serial killers as well. Their failure to develop a sense of attachment to the world as an adolescent is one trait. The most common psychological disorder associated with serial killers is antisocial personality disorder, which is a developmental disorder. People with this disorder lack empathy and are plagued with illusions of grandeur. Borderline personality disorder and narcissistic personality disorder are also quite common. All three of these disorders can be brought on by social conditions, so it is important to look at the "nurture" part of the equation.

An important similarity of serial killers is they had a tough time in their early childhood. Many were adopted, which points to potential neglect. Nearly 70% of serial killers report some kind of abuse, with over half reporting psychological abuse. When you consider that abuse can cause a number of psychological disorders, it should be considered an important social factor of psychopaths. Also, new research suggests that abuse and neglect can alter the brain's chemistry and function. Having said this, child abuse seems to be a very important factor in the development of serial killer.