Federal Bureau of Investigation scientists have adopted a new method of analyzing DNA samples, generating thousands of fresh potential leads in cold cases from the world’s largest genetic database of suspects.
The change doesn’t affect how the FBI collects or tests samples, but how it compares them at its laboratory facilities in Quantico, Va.
In May, scientists using the new methodology for the National DNA Index System generated about 7,000 fresh potential matches in the system. Those matches are now being subjected to closer scrutiny to see if they offer any new suspects or evidence in cold cases, officials said. Scientists expect many to be matches that confirm the guilt of people already caught, but others, they hope, will provide a jump-start to long-dormant unsolved cases.
In Texas, for instance, the new method generated about 1,000 new potential matches. Investigators pored over the results and determined about 65 of those could provide new information for criminal investigations, according to state forensic officials.
Tom Vinger, a spokesman for the Texas Department of Public Safety, called the new approach “extremely helpful to law enforcement, especially for cold cases in which the DNA has been degraded and testing will only produce partial results.’’
The FBI’s DNA database is like a giant computerized collection of bar codes for human beings’ genetic information. It was launched in 1998 with nine participating states, and after three years it held 800,000 DNA profiles, including known offenders and unknown suspect samples. Now fed by DNA profiles from every state, and local as well as federal investigations, today there are more than 15 million profiles in the system, making it the largest collection of such data in the world.
To find DNA matches, scientists look closely for certain parts of the genetic code that vary widely. When DNA experts find recurring patterns at certain genetic locations, or loci, in two samples, they know they have DNA samples from the same person, or from two closely related people.
The FBI’s longstanding practice was to identify “hits’’ by focusing on 13 specific locations in DNA to look for repeating genetic-code patterns. If there were matches on 10 of the 13 locations, the samples were judged as potential matches.
But starting in May, the FBI began studying its samples by looking for pattern matches at eight or nine locations.
That effort has generated thousands more potential leads, which investigators around the country are currently pursuing. A “hit’’ in the FBI system isn’t considered evidence to be used later in court, but a tip to be verified through further investigation and testing.
Officials say the new standard in no way waters down the accuracy of the work because they now understand better which genetic locations are most rare and distinctive within human DNA.
Thomas Callaghan, a scientist with the FBI’s Biometric Analysis Section, compared the new approach to sifting through vehicle traffic by searching for the more unusual makes and models of cars. It is hard to find a specific vehicle when you are searching a common car, like a dark Toyota Camry, he said—but much easier to search for a yellow Volkswagen.
“We’ve taken the dark Camrys out of the database search, and we’ve put in the yellow Volkswagens,’’ he said.
Barry Scheck, a defense lawyer and co-founder of the Innocence Project, praised the FBI’s move. “It’s a welcome development but now the responsibility falls upon the state and local authorities to expeditiously follow up on these hits in both cold cases and closed cases,” he said. “If that happens I’m confident that not only will cold cases be solved, but innocent people who are in prison for crimes they didn’t commit will also be exonerated.”
The FBI is also modernizing its DNA work by speeding up the technology used to generate immediate DNA profiles—a technique called Rapid DNA. It used to take an entire workday to develop a DNA profile. In a big case such as the Boston marathon bombing—where there was a large number of samples to be tested and an urgent need to do so to catch the suspects—scientists would have to stop all the work they were doing to refocus on a new batch of time-sensitive samples.
The FBI now has two types of machines that can identify a DNA sample in 90 minutes. Each machine costs hundreds of thousands of dollars, so they aren’t likely to replace traditional lab work, but when investigators are in a race against the clock, the machines will be extremely useful, FBI officials said.
Tina Delgado, a section chief at the Biometrics Analysis Section, said the new technology will likely speed the release of people who are tested as potential suspects.“The police officer could drive that sample over to the laboratory, run it through the machine, and we could have that person home by dinner if they were not the contributor of the DNA at that crime scene,’’ she said.
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