HELSINKI (AFP) - A simple genetic test can help predict whether psychopaths convicted of violent crimes are prone to be repeat offenders, a Finnish researcher said Tuesday.

"It has long been known that there is a biological, a genetic element to psychotic tendencies," said Helsinki University researcher Matti Virkkunen, who co-authored a study published in Psychiatric Research.

The research, which was a joint Finnish-American project, showed that convicts who scored high on both a traditional behavioural disorder test and had a certain gene variance were far more likely to commit additional violent crimes than those who scored high on the test but did not have the same gene variance.

The study followed 167 convicts for seven years after they were released from prison. All of the subjects had been convicted of aggravated violent crimes, were alcoholic, and had scored high enough on the assessment test to rate them as psychopathic.

They were also genetically tested to show a particular variance of a gene called monoamine oxidase A (MAOA).

They discovered that so-called "high activity" MAOA offenders were far more likely than "low-activity" subjects to repeat their crimes.

Specifically, for each additional point on the psychopathic assessment test, those with the "high-activity" genotype were 6.8 percent more likely to become repeat offenders.

The genetic test on its own is not enough, said Virkkunen, but it becomes a highly significant factor when added to variables such as the psychopathic assessment test, alcohol use and age.

For this reason, the researchers recommend that the genetic test be used alongside the assessment test when a convict for a severe violent crime is being evaluated for parole.