A person who commits three separate, spaced murders using a particular method of killing. (Barkan, 2006). According to FBI profiler Robert Ressler, the one who coined the term "serial killer", he remarks in his autobiography that the term is used to describe murderers seeking personal gratification, not women killing in postpartum psychosis or for financial gain.
There is no general formula for creating a serial killer, however the FBI once tried to classify killers as disorganized or organized in Douglass and other's Crime Classification Manual for the FBI. By categorizing serial killers into "organized", "disorganized" and "mixed" criminal profiles, they were oversimplifying. The problem that David Canter, a psychologist in Great Britain, found with the system was that most serial killers were organized; that''s how the crimes are continually committed without arrest.
The Biological Influences section will discuss factors such as genetics and neurological factors that are connected with antisocial personality disorder or a serial killer's family history of mental illness. Abnormalities in the brain of a murderer will also be discussed. The Psychological Influences section will discuss particular personality traits and psychiatric or psychological evaluations of particular serial killers used during or after their trial. Antisocial personality disorder as well as schizophrenia will be explained, since they are often linked to serial killers.
Childhood influences will discuss the environment the serial killer was raised in as a child, and also any abuse that may have taken place. There appears to be a direct correlation between a childhood involving physical, sexual, and/or mental abuse and the development of antisocial personality disorder, though this is not the determining factor.
These factors are important influences for everyone, not just serial killers, but these factors were specifically chosen because of the common traits associated with these influences. Below are some killers and very basic descriptions of their crimes. We will be looking at all three influences for each killer as examples.
Dr. Eric Hickey, a professor at California State University and the Director of the Center for Forensic Studies at Alliant International University. Dr. Hickey has considerable field experience working with the criminally insane, psychopaths, sex offenders and other criminals. Assembling the most extensive database on demography of serial murder, Hickey found these statistics (Hickey, 2010):