Those with the genes were 13 times more likely to have a history of repeated violent behaviour.
Many more genes may be involved in violent behaviour and environmental factors are also known to have a fundamental role.
"Committing a severe, violent crime is extremely rare in the general population. So even though the relative risk would be increased, the absolute risk is very low," he told the BBC.
This group had committed a total of 1,154 murders, manslaughters, attempted homicides or batteries. A replication group of 114 criminals had all committed at least one murder.
These all had similarly low levels of the MAOA gene, which previous research has dubbed the "warrior gene" because of its link to aggressive behaviour.
"There are many things which can contribute to a person's mental capacity. The only thing that matters is the mental capacity of the individual to understand the consequences of what he or she is doing and whether or not the individual can control his or her own behaviour."
"To some extent we're all products of genetics and the environment but I don't think that robs us of free will or understanding right and wrong."
In 2009, a court in Italy reduced the sentence of a criminal with genes linked to bad behaviour. In a similar case in the US a murderer's genetic profile was highlighted as a contributing factor for his crime.
"Studies like this really document that a large percentage of our behaviour in terms of violence or aggression is influenced by our biology - our genes - and our brain anatomy.
"It's important to conceptualise crime and violence, where it comes from, even if we would not want to radically change the criminal justice system."
"It is worthwhile to look for biological contributions to criminal or antisocial behaviour as their impact on individuals, communities and society in general is sizeable. What I think, however, is that it is vital that environmental influences are considered as well," he told BBC News.