How Reliable Are DNA Matches? FBI Blocks Access To Records.
The chance of a coincidental match may be greater than believed.
LA Times
Jason Felch and Maura Dolan
A discovery leads to questions about whether the odds of people sharing genetic profiles are sometimes higher than portrayed. Calling the finding meaningless, the FBI has sought to block such inquiry.
State crime lab analyst Kathryn Troyer was running tests on Arizona’s DNA database when she stumbled across two felons with remarkably similar genetic profiles.
The men matched at nine of the 13 locations on chromosomes, or loci, commonly used to distinguish people.
In the years after her 2001 discovery, Troyer found dozens of similar matches — each seeming to defy impossible odds.
As word spread, these findings by a little-known lab worker raised questions about the accuracy of the FBI’s DNA statistics and ignited a legal fight over whether the nation’s genetic databases ought to be opened to wider scrutiny.
The FBI laboratory, which administers the national DNA database system, tried to stop distribution of Troyer’s results and began an aggressive behind-the-scenes campaign to block similar searches elsewhere, even those ordered by courts, a Times investigation found.
The FBI estimated the odds of unrelated people sharing those genetic markers to be as remote as 1 in 113 billion. But the mug shots of the two felons suggested that they were not related: One was black, the other white.
Now, lawyers around the country are asking for searches of their own state databases.
Several scientists and legal experts as well want to test the accuracy of official statistics using the nearly 6 million profiles in CODIS, the national system that includes most state and local databases.
“DNA is terrific and nobody doubts it, but because it is so powerful, any chinks in its armor ought to be made as salient and clear as possible so jurors will not be overwhelmed by the seeming certainty of it,” said David Faigman, a professor at UC Hastings College of the Law, who specializes in scientific evidence.
FBI officials argue that, under their interpretation of federal law, use of CODIS is limited to criminal justice agencies. In their view, defense attorneys are allowed access to information about their specific cases, not the databases in general.
But Not The Guy Below