Twenty years after DNA fingerprints were first admitted by American courts as a way to link suspects to crime scenes, a new and very different class of genetic test is approaching the bench.
Rather than simply proving, for example, that the blood on a suspect's clothes does or does not match that of a murder victim, these "second generation" DNA tests seek to shed light on the biological traits and psychological states of the accused. In effect, they allow genes to "testify" in ways never before possible, in some cases resolving long-standing legal tangles but in others raising new ones.
Already, chemical companies facing "toxic tort" claims have persuaded courts to order DNA tests on the people suing them, part of an attempt to show that the plaintiffs' own genes made them sick -- not the companies' products.
In other cases, defense attorneys are asking judges to admit test results suggesting that their clients have a genetic predisposition for violent or impulsive behavior, adding a potential "DNA defense" to a legal system that until now has held virtually everyone accountable for their actions except the insane or mentally retarded.
Some gene tests are even being touted for their capacity to help judges predict the likelihood that a convict, if released, will break the law again -- a measure of "future dangerousness" that raises questions about how far courts can go to abort crimes that have not yet been committed.
Most of these tests are still research tools hovering on the margins of admissibility; only a few have made the leap from the lab bench to the courtroom. But scientists' expanding ability to query people's genes, and lawyers' efforts to introduce those findings as evidence, are forcing scholars and judges to think in new ways about the Constitution's protections against self-incrimination and unreasonable search and seizure.
At its extreme, the prospect of getting an accurate handle on future dangerousness challenges the very notions of autonomy and free will that are at the core of any theory of criminal responsibility.
"So far, judges have been cautious," said Karen Rothenberg, dean of the University of Maryland School of Law. But given what Rothenberg calls the "love affair" that courts have had with DNA fingerprints, she and others fear that judges and juries will fall too quickly for the new tests.
"As the cost of gene testing comes down . . . we're likely to see clever defense counselors taking steps to use the outer reaches of genetic testing," said Judge Andre M. Davis of the U.S. District Court for the District of Maryland, speaking at a recent Baltimore roundtable co-sponsored by the law school and the National Human Genome Research Institute. "The question is, can the judge manage the case so the jury is not taken down the primrose path of genetic test results?"
Shadows of Eugenics
Genes have had a rocky relationship with justice, dating at least to the early years of the last century, when eugenics laws encouraged forced sterilizations to break the cycle of "inherited criminality."
"Shiftlessness, nomadism, pauperism all were assumed to have biological and genetic causes," said Jeffrey R. Botkin, a physician and ethicist at the University of Utah School of Medicine.
Today, Botkin said, scientists know that genes are only part of what adds up to human health and behavior. But with environmental influences more difficult to pin down and a torrent of new, if preliminary, DNA findings to choose from, lawyers and judges are once again being tempted to lean heavily on genes to help them make difficult legal decisions, he said.
Civil courts were the first to start admitting and in some cases even compelling second-generation DNA tests. A survey led by Rothenberg and University of Maryland Associate Dean Diane Hoffmann found that in 127 court cases that involved health-related DNA information, more than half had to do with medical malpractice, and most of those were birth-injury claims in which a parent blamed a doctor for a child's neurological or developmental problems. Judges have increasingly granted doctors' requests that such children be tested for fragile X syndrome, the most common form of inherited mental retardation.
The tests can bring much-needed evidence to bear but can also be intimidating -- a potential boon for the doctors. In several instances, parents have either dropped or settled their cases rather than submit their children to a definitive diagnosis that could affect their eligibility for health insurance.
In one case, a mother sued a doctor and a hospital, claiming that negligence during her labor and delivery caused her daughter permanent brain injuries. A geneticist suspected that the girl had Angelman syndrome, a rare disease caused by a defective chromosome. The trial court ordered a DNA test, but the mother refused, resulting in her not only losing the case but also being held in civil contempt.
Similar tactics have been used in "toxic tort" cases, in which people sue alleged polluters for causing their medical problems. In these cases, judges can compel tests that look for the hallmarks of DNA damage caused by certain chemicals.
Plaintiffs have prevailed when the signature DNA injury was found. By contrast, in a case in which a company was sued by people who blamed their various ailments on the company's benzene pollution, the company was found not liable after tests on the plaintiffs did not find the telltale DNA changes caused by benzene.
Measuring a Life Span
Less well developed but potentially more contentious are genetic tests that can help predict how long a person will live.
Anticipated life span can be a big factor when deciding how much a wronged person deserves in money damages -- for example, how much a person might have earned over a lifetime if she had not been disabled by a drunken driver. Toward that end, courts have long admitted crudely predictive evidence such as whether the person already had a terminal disease, smoked cigarettes or engaged in "intemperate habits." Some have even compelled tests for the virus that causes AIDS.
Now life-span testing has expanded into the genetic arena, and not just to calculate damages. In one child custody case, a judge granted the father's request that the mother get tested for the gene that causes Huntington's disease, an inherited and incurable disorder that causes dementia in midlife. Half of individuals who have a parent with the disease carry the ticking time bomb, and most choose not to learn their status in advance. When the judge granted the motion, the mother fled the jurisdiction, giving the father a victory, but not on the merits of his custody arguments.
Many genes contribute to longevity; just last month, researchers announced the discovery of more than a dozen genes newly suspected of helping determine a person's life span. Even if all of them were known, they could at best provide a probabilistic estimate. But as those estimates become more accurate, said Hoffmann, the Maryland associate dean, they will force judges and jurors to think hard about a question that has long dogged legal scholars: Should damage awards be linked to projected life span at all?
"If it's for compensation, then yes, that means you'd want to fine-tune it to the details of the individual and their personal life expectancy," Hoffmann said. "But if damages are about deterrence, then that says you don't get off the hook just because you were lucky enough to hit someone who had a short life expectancy."
The stakes are much higher and the ethics more complex when second-generation genetic tests enter the criminal courtroom.
U.S. courts have long recognized that criminal responsibility requires a certain modicum of mental acumen. Beyond the well-known plea of insanity, some states recognize a "diminished capacity" defense. And a 2005 Supreme Court decision barred capital punishment for offenders younger than 18, citing scientific findings of an "underdeveloped sense of responsibility" in minors.
But what 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."
The Supreme Court of South Carolina reversed a murder conviction for a man who shot a shopkeeper in the head, concurring with the killer's attorney that his actions were an outgrowth of severe, genetically rooted depression -- essentially saying that what he did was the result of an inherited disease rather than an act of free will.
But in a 2001 first-degree murder case, a Tennessee court rejected the defendant's claim that an inherited predisposition to depression and mental illness made him incapable of a premeditated act.
All told, defendants hoping to convince juries of their innocence, or at least garner enough sympathy to avoid the death penalty, have had better luck invoking family histories of mental illness than specific gene tests to raise doubts about their culpability. But that is likely to change, experts say, as specific genes get more definitively linked to violence and impulsivity.
One case that may prove to be a harbinger took place in the 1990s, after Stephen A. Mobley was convicted of murdering a Domino's Pizza store manager in Georgia. Hoping to avoid the death penalty, his attorneys asked the court to pay for tests to find out whether Mobley, who came from a family with a history of violent behavior, harbored a mutant gene for a brain enzyme known as MAO-A.
Scientists had just pegged a Dutch family's multi-generational history of fistfights and run-ins with the law to that mutant gene. But the judge in Mobley's case found the association too new, and Mobley was executed in 2005.
Since then, however, a number of studies have strengthened the link between MAO-A and violent behavior, and other genes have been added to the mix. This month, scientists in Israel reported that a version of a gene called AVPR1a is associated with "ruthlessness." And although such tests can offer only the probability that a given behavior will arise, they can sway jurors, experts said, because they seem more scientific than a doctor's clinical assessment.
It is probably only a matter of a time before gene tests are admitted in a criminal trial, at least as evidence in the sentencing phase, said Deborah W. Denno, a professor at Fordham Law School.
"The word 'genetic' is such a loaded term. It's very touchy stuff," Denno said. But it is not as though the kind of testimony already being used in sentencing is particularly scientific, she added.
"The mere fact that your family loves you or that you go to church is allowed as mitigating evidence in a death penalty case," Denno said.
How Juries Will React
Whether evidence of an inborn penchant for violence can be relied upon to evoke a jury's sympathies is another question, and there is some reason to doubt it.
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."
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