DNA Tests Offer Deeper Examination Of Accused

After Jeffrey Landrigan was sent to death row in Arizona for fatally strangling and stabbing a man -- this, after a previous conviction for murder and an incident in which he stabbed a fellow inmate -- he appealed his sentence to the Supreme Court, claiming that his attorney failed to present evidence of his genetic predisposition to violence.

He lost his plea, but the written opinion of one lower court judge suggested that, had he won, the evidence might have done Landrigan more harm than good.

"The potential for future dangerousness . . . inherent in Landrigan's alleged genetic pre-disposition for violence would have negated its mitigating capacity for evoking compassion," the judge wrote.

Similarly, in 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.

Nonetheless, given the potential gravity of second-generation DNA test results, legal scholars have begun to consider the constitutional issues surrounding them.

Several courts have said that taking a blood sample or cheek swab for the purpose of getting DNA is simple enough as to generally not constitute a violation of the Fourth Amendment protection against unreasonable searches. But a different standard may be appropriate if the DNA is going to be used for more than simple identification.

"The standard right now is just 'How physically invasive is it?' " Farahany said. "But the kind of information being obtained should be a factor. It's a pretty serious invasion of privacy to get information that is that content-rich."

Similarly, when interpreting the Fifth Amendment protection against self-incriminating testimony, the Supreme Court has said that the word "testimony" should be taken to mean spoken words. But given scientists' increasing ability to understand the language of DNA, scholars say, that interpretation may need some refinement.

"The courts haven't really faced that issue yet," Farahany said. "But it's a lot like witnessing against yourself."