There are several competing schools of thought as to what creates a monster like Theo Durrant. Pinkerton's statement that the criminal is one who "flings aside conscience" represents the view that criminal behavior, including violent crime, is a chosen lifestyle.
This theory, developed by Dr. Samuel Yochelson and further refined by his protégé, Dr. Stanton Samenow, believes that "criminals choose to commit crimes."
"Crime resides within the person and is 'caused' by the way he thinks, not by his environment," writes Samenow. "Criminals think differently from responsible people."
Samenow's theories argue that focusing on forces outside the criminal — environment, society, poverty — is futile and will do nothing to reduce criminal activity. The change must come from within.
Another school takes a more neuro-psychological view of the causes of crime.
Dr. Jonathan Pincus, a Georgetown neurologist, in Base Instincts has proposed a three-pronged theory of mental illness, physical brain damage and psychological trauma such as abuse which produces people like Theo Durrant.
"Abusive experiences, mental illness and neurological deficits interplayed to produce the tragedies reported in the newspapers," Pincus writes. His theory explains not only lust murders like Durrant's but the seemingly random acts of violence that fill the pages of the local papers.
"The same complex of factors underlies the act of homicide," Pincus said. "Attacks on strangers are substantially the same, etiologically, as attacks on friends. Regardless of the classification of killing, I believe most killers kill for the same reasons."
Pincus based his theories on the research he conducted with Dr. Dorothy O. Lewis who spent considerable time studying violent juveniles in search of a causal theory of crime. Lewis's theory is that violence is displaced rage against an abusive authority figure that is "vented" on an innocent victim.
But what causes this rage? To Lewis, the rage is the final stop in a long process: "First, physical abuse often causes central nervous system damage, thus contributing to impulsivity, attention disorders and learning disabilities," she writes. "Second, it provides a model with which to identify. Finally, it engenders rage toward the abusing parent, rage that can be then displaced onto authority figures and other individuals."
A final theory of the origin of killers is the one proposed by criminologist Dr. Lonnie Athens. He takes a position similar to Samenow's in that "violent criminals know what they are doing when they decide to act violently," according to his biographer, Richard Rhodes.
"Athens' discovery... means that murders are never senseless from the murderer's point of view; that motives, however 'trivial' and 'apparently unimportant' they may seem to psychologists do inform violent criminal acts; that violent criminals do not 'snap' but make decisions and act on them" and that if a criminal will answer honestly, it is possible to know why the act was committed.