Scientific Study of Genes' Effect on Behavior

 Posted on April 21, 2008 in Uncategorized

Here's an excerpt from yesterday's Washington Post article by Rick Weiss on the use of DNA evidence in court for reasons other than identification:

... [W]hat of the murderers, rapists and other violent criminals who fall outside those narrow bounds? Can some, at least, blame their behavior on their genes?Studies have shown that up to 62 percent of antisocial and criminal behavior is "heritable," a rough measure of a genetic contribution. And in a few cases, courts have allowed arguments seemingly akin to "My genes made me do it."

Weiss discusses several cases in which defendants have sought to have juries consider genetic predispositions to depression, mental illness, and violent behavior.

In discussing "[w]hether evidence of an inborn penchant for violence can be relied upon to evoke a jury's sympathies", Weiss writes:

[I]n a rare case in which a court did accept evidence of a defendant's inborn "propensity to commit murder," that court, in Idaho, considered it an aggravating factor, not a mitigating one, and used it to help justify the death sentence.Such decisions are worrisome, said Markus Heilig, a research psychiatrist and neurochemist at the National Institute on Alcohol Abuse and Alcoholism. "To argue that behavior can be predicted, you are arguing this guy does not have free will," Heilig said. "So how can you hold someone accountable?"Not everyone goes that far."Just because you can explain a behavior's cause doesn't mean it is excusable," said Nita Farahany, an expert in behavioral genetics and the law at Vanderbilt University.

Heilig and Farahany are clearly speaking different languages; they're both correct.

A genetic predisposition to violence is a double-edged sword. It reduces a person's moral blameworthiness (whether he can be held accountable) while making it more likely that the person will be a danger in the future; retribution becomes a smaller punishment factor but specific deterrence and incapacitation become greater ones.

New York criminal-defense lawyer Scott Greenfield asks "where to draw the DNA line". He's talking about the use of DNA databases to find family relationships between questioned DNA samples and known DNA samples. Consider Scott's question in light of advances that are starting to allow scientists not only to match questioned DNA with known DNA, but also to identify those DNA donors who are more likely some day to commit crimes.