Where Genetic Influences Leave off and State of Mind Takes Over

Sunday, April 20, 2008

For defendants to be found guilty of a crime, a court generally must conclude that they were aware of their actions and also had what lawyers call "mens rea," literally a "guilty mind" -- a recognition that their actions were wrong.

Being unconscious has been accepted as a criminal defense since the 1870s, when a man named Fain with a history of sleepwalking had his murder conviction reversed after convincing the court that he was asleep when he shot his victim.

Similarly, people responsible for fatal auto accidents have been declared not guilty when it was shown that they had an epileptic seizure while driving -- though they can be found culpable if it happens a second time, on the presumption that they should have known better than to drive again.

Still to be decided by the courts is whether a genetic test that shows, for example, that a person has a gene-based difficulty controlling impulses, or a strong predisposition to a psychotic illness such as schizophrenia, deserves to be treated like a somnambulist or a person having a perpetual seizure.

DNA test results may someday reduce a sentence or even help people avoid conviction, but for now that bar is high because genetic tests are general and cannot speak to the precise state of a person's mind at the moment the crime was committed.

Rick Weiss

© 2008 The Washington Post Company