Genetic genealogy technology to be used in Nancy Guthrie case has helped solve Tampa Bay area cases

ST. PETERSBURG, Fla. - Investigative genetic genealogy, which is a relatively new forensic tool, is now being considered in the search for answers in the Nancy Guthrie case.

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Investigators say DNA was recovered from a glove found near Guthrie’s Tucson home. However, that DNA did not produce any hits in CODIS, the national law enforcement DNA database.

RELATED: Nancy Guthrie: DNA profile found on glove did not match anyone in CODIS system

Now, experts say genetic genealogy could provide another path forward, even without a direct match. 

The technique gained national attention in 2018 when it was used to identify and arrest the Golden State Killer. Since then, experts say it has become a routine tool in cold case investigations across the country.

Investigative genetic genealogists use DNA differently than traditional testing. Instead of looking for an exact match, they analyze a broader genetic profile to find potential relatives in opt-in genealogy databases.

"You can think of an STR profile as just like a fingerprint. It tells you if you have the right person," said Ed Adams, an investigative genetic genealogist with Moxie Forensic Investigators. "An SNP profile, on the other hand, is like a roadmap that tells you how to find the right person."

Those "roadmaps" are created using public, opt-in databases such as GEDmatch, Family Tree DNA and DNA Justice, where users have voluntarily shared their DNA results from websites like Ancestry, 23andMe and more. From there, genealogists begin building family trees based on DNA matches, often tracing distant relatives across multiple generations.

"You start building out family trees until you’re able to make connections between those DNA matches," Adams said.

Why you should care:

The same technology has already been used to resolve cold cases locally. Last year, forensic genealogists helped Clearwater police identify Edman Gleed as the John Doe found near the Clearwater Pass Bridge in 1993, finally giving answers to his family decades later.

This month, St. Petersburg cold case detectives used genealogical techniques to identify a murder victim who had been known as "John Doe" for 46 years: Johnny Bradshaw, who was 29 when he was killed at the Siesta Motel. 

RELATED: St. Pete's last 'John Doe' homicide victim identified after 46 years through DNA technology

Investigators said Bradshaw’s sisters had been searching for him for decades.

Experts say those cases highlight how genealogy can succeed where traditional databases fall short.

"CODIS is phenomenal, but it’s great for identifying an individual person," Adams explained. "If the person you’re looking for is not already in the database, you’re left with not a lot of options until investigative genetic genealogy came along."

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Despite its success, experts caution the process is often time-consuming and labor-intensive. Cases can be solved in a matter of hours or take years, depending on DNA quality, database matches and the complexity of family histories.

"We’ve had cases that we have solved in hours, and we have had cases that we’re still working on two years later," Adams said.

Another challenge is public hesitation. Detectives say when people are contacted out of the blue about DNA or family connections, cooperation can take time and trust-building.

READ: Cracking unsolved cases: Hernando County launches rapid DNA technology

"Obviously, if you’re a person and someone calls you out of the blue and says they’re a detective, and they want a DNA sample from you, you’re probably going to be hesitant," said St. Petersburg Detective Wally Pavelski. "That definitely takes some convincing for a lot of people."

What's next:

Genealogy experts say people who have taken consumer DNA tests through services like Ancestry or 23andMe are not automatically searchable by investigators. 

Only users who voluntarily opt into specific law enforcement-accessible databases can help generate potential matches.

"If you feel moved by these sorts of cases, like the Nancy Guthrie case or any of the other number of cold cases that are being solved daily using IGG, I would encourage them to look at websites like GEDmatch, Family Tree DNA, and DNA Justice," Adams said.

As investigators continue to examine the DNA evidence in the Guthrie case, experts say each new genetic profile added to opt-in databases could help connect the dots and potentially bring long-awaited answers to families still searching for closure.