The concept of a "crime gene," and the explanation "my genes made me do it," are gaining in acceptance among many researchers. This development is generating novel challenges in criminal prosecutions.
In 1907, Sir Francis Galton first put forward the theory of "inheritance of criminal tendancies." Since then, sophisticated studies have increasingly confirmed a genetic basis for some criminal actions.
"Genetics and molecular biology have provided some significant insights into behaviour associated with inherited disorders," confirmed Joseph McInerney of the Foundation for Genetic Education and Counseling.
Recently, the Italian judiciary reduced the sentence of a convicted murderer on the grounds that his genes predisposed him to commit homicide.
"The odds of becoming a criminal are not equal at birth," suggested Irving Gottesman of the University of Virginia.
Preliminary information indicates that most criminal behaviour could be inescapably inherited.
"Individuals with these genes could find themselves engaging in criminal activity," suggested Caitlin Jones at Rochester Institute of Technology. "There is a genetic component to criminal behaviour."
Increasingly, defence attorneys are requesting that judges admit evidence suggesting clients are genetically predisposed towards violent or other criminal actions -- the so-called "DNA defence."
At issue is a body of research linking criminal behaviour to certain inherited genes. A 2008 study at Hebrew University in Israel identified argenine vasopresser receptor-1 (AVPR1 gene) as a cause for "ruthless" behaviour. Research in 2009 by Rose McDermott at Brown University uncovered a "warrior gene" responsible for high levels of aggression in response to provocation.
In 1995, a Dutch study showed that males in a family whose members repeatedly engaged in crime had a mutated monoamine oxidase-A (MAOA) gene. Recently, Kevin Beaver's research confirmed that boys with mutated MAOA genes are more likely to join gangs.
Last year, Guang Guo and colleagues showed the same MAOA variant generates violent delinquency. Research at the Civic Research Institute suggests MAOA is a "disinhibiting" gene, and mutations make people more likely to commit crimes.
According to Debrah Denno at Fordham Law School, "many people who commit homicides also have... relatives who are incarcerated."
She explained that "genetic mitigation" can show that an offender might not be responsible for his actions.
Sarnoff Mednick at the University of California confirms that adopted children whose biological parents are criminals are much more likely to become criminals themselves, even if their adopted parents are law-abiding.
If criminals are genetically pre-programmed to commit crimes, then the assumption that incarceration might reshape criminal behaviour could be flawed. According to a 2003 ruling of the New York Supreme Court, genetic predispostion evidence raises the ugly matter of "future dangerousness."
Of critical significance, as pointed out by philosopher Don Brock, is the conundrum that if an individual's genes are a principle cause of behaviour, and if those genes are unalterable, and their effects unchangeable, is it justifiable to be held responsible for the resultant actions?
Robert Alison has a PhD in zoology and is based in Victoria, B.C.