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To investigators aiming to crack decades-old cold cases, few tools are as powerful as DNA evidence, the so-called "gold standard" of forensic science, authorities say.

As the search continued Thursday at the farm where Jacob Wetterling was last seen, observers said advances in DNA technology make it possible for investigative riches to still be found -- even in a 1989 abduction case.

They say the state Bureau of Criminal Apprehension also has the rare ability among law enforcement agencies nationally to unlock DNA potential in bone fragments and other scant or degraded evidence.

There, on the third floor of BCA headquarters in St. Paul, behind double security doors, is a lab opened in 2005 to conduct mitochondrial DNA testing -- the same technique used on mummies, mammoths and Neanderthals.

St. Paul police Senior Cmdr. Tim Lynch, who has overseen his department's cold-case investigations, said St. Paul police relied on the lab to confirm from a bone sample the identity of a woman whose body was found in a car pulled from the Mississippi River.

Authorities turn to mitochondrial DNA when traditional nuclear DNA -- commonly drawn from blood, semen or skin -- is unavailable. The new technology, dating to about 2000, can create usable evidence out of bone fragments, teeth, strands of hair -- even fingernails, said Dixie Peters, a technical leader at the Center for Human Identification at the University of North Texas Health Science Center.

Peters said Thursday that the technology is so new that even if bones had been uncovered in an investigation 20 years ago, they probably would have ended up in "some law enforcement agency's closet."

At St. Paul police headquarters, Sgt. Anita Muldoon said she was not privy to any inside details on a revived Wetterling investigation. But, as her department's lead cold-case investigator, she said she is fascinated by the news.

"It gets me excited," she said. "I want to be up there [in St. Joseph] helping dig in the dirt. I'd love to know what they are up to or what they are using."

Anthony Lonetree • 612-673-4109