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DNA tests on felons' kin proposed
The Washington Post
WASHINGTON — Police would solve more crimes if they expanded their use of the nation's DNA fingerprinting system to test close relatives of known criminals, according to a report that raises civil-liberties issues.
The proposed crime-control strategy, in growing use in England, is based on two central facts: Close relatives of criminals are more likely than others to break the law and, because those individuals are related, their DNA "fingerprints" will be similar.
That suggests that if police find a crime-scene specimen with a DNA pattern close to — but not exactly the same as — that of a known lawbreaker, a relative of that known criminal may be the culprit.
In England, where rules governing the use of DNA for crime fighting are more permissive than in most U.S. states, the approach has been used dozens of times and has helped solve several cases, said Frederick Bieber, a Harvard medical geneticist who led the new study with colleague David Lazer and Charles Brenner of the University of California, Berkeley.
In one recent case, for example, a specimen from a 1988 murder scene was found to have a DNA pattern similar to that of a 14-year-old boy whose DNA was on file with the police. Investigators obtained a sample from the boy's uncle, which perfectly matched the crime-scene specimen and led to his conviction.
The new analysis, published Thursday in the online edition of Science, is the first to use sophisticated computer models to predict how useful such familial searches may be.
The computation is based on well-established facts, such as the prevalence of certain DNA variants in the population, and less precise assumptions, such as the odds that a criminal has a close family member whose DNA is already on file.
In the United States, those odds are rather high: A 1999 Justice Department survey found that 46 percent of jail inmates had at least one sibling, parent or child who had been incarcerated at some point.
All states take DNA from all convicted felons, and many get specimens from a wide range of others.
Using conservative assumptions, Bieber and his colleagues calculate that U.S. law-enforcement authorities could increase their "cold-hit" rate (the percentage of DNA searches that result in perfect matches) by 40 percent if they were to check the DNA patterns of criminals' family members when searches generate near-misses.
The approach raises hackles among many civil libertarians, who note that England does not have a Bill of Rights. Under the Fourth Amendment, U.S. authorities are generally required to show compelling evidence that an individual has committed a crime before demanding a DNA sample.
"If I give up a sample, does that mean I've also committed all my blood relatives to a search?" asked Carol Rose, executive director of the American Civil Liberties Union of Massachusetts. "That's where the technology is moving faster than the law."
Familial testing would also amplify racial inequities in the criminal-justice system, which already focuses disproportionately on blacks, said Troy Duster, a New York University sociologist.
In the United States, where the DNA fingerprints of about 3 million people are stored in a national criminal database, familial testing has only rarely been acknowledged.
Tom Callaghan, custodian of that database, said the FBI does not pursue partial matches.
But no state is precluded by law from using the approach. And at least two — New York and Massachusetts — have statutory language expressly allowing it.
Bieber acknowledged that the strategy could impinge on civil liberties.
"It's a balancing act," he said. "But I think we are duty-bound to explore the potential."
Material from The Associated Press
is included in this report.
Copyright © 2006 The Seattle Times Company