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Courtroom Genetics

Genes and how they may influence criminal behavior are increasingly finding their way into the US court system where, Paul Appelbaum from the NY State Psychiatric Institute cautions in Neuron this week, they are at risk of being misinterpreted.

In the past, Appelbaum writes, judges have erroneously relied on genetics to justify the forced sterilization of people with intellectual disabilities, and defense attorneys have tried to link XYY karyotypes to an unavoidable propensity for violence that renders defendants not responsible for their actions.

Most of the time, he notes, the influence of genetics on behavior arises during sentencing, especially in death penalty cases, when judges can consider mitigating factors However, Appelbaum writes that the link between certain genes, including MAOA, and violent behavior is tenuous.

"Courts’ responses to attempts to introduce these data have been mixed, with some excluding it on the basis that the science has not been developed sufficiently to establish the validity of the relationship between the genetic findings and the defendant’s behavior," he adds.

Genetics is also finding its way into the civil court system, being used in ways that Virginia Hughes at Only Human describes as "shocking."

For instance, Appelbaum describes a case in Canada in which a woman sued her landlord for injuries she received after a fire in her building. The court compelled the plaintiff, who has a family history of Huntington's disease, to undergo genetic testing to determine whether the injuries could be due to that condition.

"In these civil cases, which are not usually matters of life and death, I would imagine that the bar for scientific scrutiny would be set lower than in criminal cases," Hughes writes. "That’s troubling, and all the more reason that we need to better educate the public about what genes can and cannot tell us."