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Detectives are hoping a murderer's biological link to the nation's colonial past will help identify him in the 1991 killing of a Washington teenager.

A DNA profile from the suspect was recently sent to a California outfit that specializes in forensic genealogy — and the analysis shows that he is distantly related to three passengers who arrived in what is now Plymouth, Mass., on the Mayflower in 1620. The forensic genealogist who did the analysis believes there's a decent chance that the killer shares their last name, Fuller.

"Our first thought was, 'What are we going to do with that?'" King County sheriff's detective Jim Allen said Wednesday. "But maybe that'll be the extra tidbit that will generate that one phone call, that one tip we need to help solve the case."

Sarah Yarborough, a 16-year-old from the Seattle suburb of Federal Way, was last seen alive on a Saturday morning in December 1991, when she left home to take part in a dance team competition. Her body was found, sexually assaulted and strangled, on the campus of Federal Way High School later that morning.

Despite the detailed descriptions that witnesses gave — they saw a white man in his 20s, 6 feet tall or just under, with shoulder-length blond hair, a trench coat and dark pants in a brushy area near the body — investigators could never identify him. Plugging DNA recovered from the body into investigative databases didn't help, either. Investigators ruled out some suspects using DNA and even hypnotized one witness in hopes of improving her memory.

After joining the sheriff's cold-case team last November, Allen spoke with one of the scientists from the state's crime lab who had worked on the case. She suggested he try Colleen Fitzpatrick, who runs Identifinders International of Huntington Beach, Calif.

Fitzpatrick has a background in nuclear physics, but she's found a second career in using forensic genealogy — genealogy assisted by DNA profiles — to track people down or help find relatives. She noticed that the killer's DNA strongly correlated with DNA profiles published as part of a genealogical study of the Fuller family.

Specifically, she said, the killer is a descendant of Robert Fuller, who arrived in Salem, Mass., in 1630. Fuller was not himself on the Mayflower, but he was related to three passengers: Edward Fuller, as well as Edward Fuller's brother, Samuel, and 12-year-old son.

Fitzpatrick said her analysis followed the Y chromosome — the male line of the family — and therefore, there's a good chance the killer's last name is or was Fuller.

"We don't dig up 400-year-old people or anything like that," she said. "I don't know who gave the DNA, but these people have worked out their family trees pretty well. DNA has become a very big deal for genealogists in the last 10 years."

Detectives have searched through their tip database regarding Yarborough's killing, but no one named Fuller has ever been fingered as a potential suspect, Allen said.

Today, there are tens of millions of people descended from the 102 passengers and about 25 crewmembers who arrived on the Mayflower, according to the General Society of Mayflower Descendants. Nine presidents have been related to those original Pilgrims.

Fitzpatrick picked up genealogy as a hobby and several years ago wrote a book on using DNA to identify relatives. Eventually, a company that works to return unclaimed property to its owners or their heirs hired her as a consultant, and she had a blast tracking down people around the world.

In 2008, she used the techniques to help solve a mystery stemming from a 1948 plane crash that killed 30 people on the side of an Alaskan mountain. Half a century later, the crash site was discovered, along with some remains that had been mummified in a glacier.

Fitzpatrick tracked down a distant living relative of one of the crash victims in Ireland. The relative provided a DNA sample, which, along with a newly developed fingerprinting technique, proved that a frozen hand recovered from the crash scene matched that victim.

Fitzpatrick says she has also tracked down a distant cousin of Amelia Earhart's navigator, Fred Noonan, who agreed to provide a DNA sample. If the remains of the famous pair, who disappeared over the Pacific in 1937 as Earhart tried to circumnavigate the globe, are ever located, Fitzpatrick has the DNA ready to prove the link, she said: "The solution to that mystery might be in my freezer."

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Online:

www.identifinders.com

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Johnson can be reached at https://twitter.com/GeneAPseattle