In this photo taken Thursday, Feb. 21, 2013, an inmate at the Madera County Jail is taken to one of the inmate housing units in Madera, Calif. Rich Pedroncelli/AP Photo There is no easy explanation for why some people commit crimes and others don't.

Similarly, there's no easy answer to the question of why some people end up in jails and prisons while others do not. It's a mathematical reality that the American criminal justice system disproportionately punishes poor people and black people for the same crimes as wealthier and white people.

But at the same time, the population of people who end up in prison do share some traits. And scientists have now traced one common criminal trait to specific genes.

Antisocial Personality Disorder (ASPD) is wildly overrepresented in prisons. Take a crowd of 100 people of the street, and chances are just one to three of them will have ASPD. Take 100 people from a prison, and you can expect 40 to 70 of them to have the disorder.

That's significant, because ASPD has been linked with aggression, irritability, disregard for rules, disregard for other people, and dishonesty.

It's a controversial diagnosis — broad, ill-defined, and overlapping heavily with other disorders like psychopathy.

But there's reason to take it seriously. Twin studies suggest that genetics explain about half of the variance in ASPD diagnoses, and environmental factors the other half. And a new study has begun the task of identifying which genes are most likely involved in ASPD, with significant success.

An international team of Finnish, American, British, and Swedish researchers examined data from the Finnish CRIME sample — a database of psychological tests and genetic material from 794 Finnish prisoners taken between 2010-2011.

The findings of this study cannot be implemented for any prediction purposes, or brought into courthouses to be given any legal weight.

Of the 794 prisoners, a full 568 screened positive for ASPD. By comparing that group's genetic material to a large control sample from the general population, the researchers identified a number of genes that may play a role in at least some ASPD cases.

The study's results are interesting in and of themselves — advancing our understanding of ASPD from Genetics seem to play a role to These genes seem to play a role. This seems to be the first time researchers have made this leap with a personality disorder.

But just as interesting are the concerns the researchers express about how their research might be misused.

"The findings of this study cannot be implemented for any prediction purposes, or brought into courthouses to be given any legal weight," they write.

In the past, claims about specific genes and violence have been — in the researchers' words — "misused" by prosecutors as evidence that defendants are violent. And as more studies like this one link specific genes to the potential for violence, that danger only grows.

There are valid, important reasons for scientists to deepen their understandings of disorders like ASPD, but also real danger of people's genes being used as evidence that they are criminals.