I found this link via Fark. Some violent criminals have attempted a defense based on their genes predisposing them to violent anti-social behavior. Some variants mentioned are MAO-A and AVPR1a, which you may be familiar with if you read Gene Expression. At least on one occasion the defendant got off on the basis of his act not being a result of “free will” due to his genetic condition. I of course find the entire concept of “free will” to be incoherent and a blemish on our justice system. A sensible take on the issue is in Greene & Cohen’s “For the law, neuroscience changes nothing and everything“. If you really are hard-wired to kill, all the more reason to get rid of you as we might a rabid dog.