Genetic genealogy that caught notorious killers now used in Nancy Guthrie case

Investigators looking to track down Nancy Guthrie’s suspected kidnappers are turning to a relatively new technology that has been attributed to solving some of the most prolific criminal and cold cases in American history. 

Investigative genetic genealogy (IGG) is defined as “the science of using genetic and genealogical methods to generate leads for law enforcement entities investigating crimes and identifying human remains,” according to the International Society of Genetic Genealogy. 

Investigators use a DNA sample to search for genetic familial matches, ultimately looking to narrow down potential identities by zeroing in on close relatives of the individual. 

On Tuesday, the FBI confirmed to Fox News Digital that IGG was being used to test DNA found on a black glove discovered two miles from Nancy Guthrie’s home and other DNA samples found inside her house.

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The move comes after both samples did not find a match in the nationwide law enforcement database, CODIS – which only includes individuals previously known to authorities.  

The technology has been used to solve several high-profile cases in recent years, with the FBI now turning to IGG in hopes of identifying the DNA found on the glove discovered two miles from Nancy Guthrie’s home and other samples located inside the house. 

Here is a look at previous cases in which IGG helped authorities locate their suspect.

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The Idaho Murders

Immediately following the brutal murders of four University of Idaho college students on Nov. 13, 2022, investigators raced to track down the person responsible for killing Madison Mogen, Ethan Chapin, Xana Kernodle and Kaylee Goncalves.

Using DNA found on a Ka-Bar knife sheath left behind at the crime scene, authorities sent samples to forensics lab Othram after coming back empty-handed when using CODIS.

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Othram was then able to create a DNA profile that matched items pulled from Bryan Kohberger’s family trash at their Pennsylvania home, leading investigators to “a male as not being excluded as the biological father of Suspect Profile,” according to the affidavit. 

Kohberger was subsequently taken into custody on Dec. 30, 2022 and pleaded guilty to the quadruple murders last summer as part of a plea deal to escape the potential death penalty. 

He is serving four consecutive life sentences, plus another 10 years.

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The Golden State Killer

More than three decades after 13 people were murdered and dozens more raped, IGG led investigators to finally track down one of the most prolific killers in California’s history. 

Using DNA collected from the crime scene, authorities were able to match a profile created for the Golden State Killer to online genetic profiles. The results pointed investigators toward a relative of former police officer Joseph James DeAngelo, who was arrested in 2018 and later charged with dozens of crimes.

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“We were confident that he was born between 1940 and 1960,” Paul Holes, a former investigator with the Contra Costa County Sheriff’s Office, told Fox News during a 2021 interview for the Fox Nation documentary and Fox News Audio Podcast “Grim Tide: Hunting the Long Island Serial Killer.”

“The common ancestors that we used were great, great-grandparents. These were people who were born in the 1840s, and we built a family tree that consisted of thousands,” Holes said. “And then ultimately, we landed on a California branch with a small number of… males of the right age. And then, at that point, it’s just ‘Investigation 101.’ Who are these men and could any of them be somebody that we need to look at closer to being the person that is responsible?”

Prosecutors previously called DeAngelo’s decades of crimes “simply staggering,” encompassing 87 victims at 53 separate crime scenes spanning 11 California counties.

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DeAngelo pleaded guilty to 13 murders and 13 rapes in 2020, and was later handed multiple life sentences without the possibility of parole. 

Bear Brook Murders

Nearly 25 years after the body of an unidentified little girl was discovered in a 55-gallon drum barrel near New Hampshire’s Bear Brook State Park, investigators used genetic genealogy to crack the final name included in the infamous Allenstown Four.

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From 1985 to 2000, authorities located four bodies stuffed in barrels in what was later ruled as homicides, with three of the individuals being identified as Marlyse Elizabeth Honeychurch, 24, and her two daughters, Marie Elizabeth Vaughn, 6, and Sarah Lynn McWaters, 1. 

However, the identity of the final victim remained unknown until 2025, when authorities used genetic genealogy to determine the young girl was Rea Rassmussen, according to the National Center for Missing and Endangered Children.   

All four victims are believed to have been murdered by serial killer Terry Peder Rasmussen, the biological father of Rea, who was suspected of killing at least six women and two children prior to his death in 2010.

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The break in the case came in 2024, when the New Hampshire State Police partnered with the DNA Doe Project and learned the unidentified child’s mother was a woman named Pepper Reed. 

Reed’s family reportedly told investigators she was last seen in Texas during Christmas of 1975, and later moved to California while pregnant. Her family identified Terry Rasmussen as the father of the child, which was later confirmed by a birth record located in Orange County, California.

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Using DNA samples from Reed’s sole surviving sibling, investigators were able to confirm Rea Rassmussen’s identity. She is believed to have been between the ages of 2 and 4 when she was killed. 

However, Reed remains missing and is believed to have been murdered by Terry Rasmussen, who was later convicted of killing girlfriend Eunsoon Jun in 2002.

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William Talbott II

In a first-of-its-kind trial using genetic genealogy testing, William Talbott II was found guilty of murder in the 1987 deaths of a young couple from Canada, Jay Cook, 20, and Tanya Van Cuylenborg, 18.

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Investigators identified Talbott as a suspect after uploading DNA found at the crime scene to the public genealogy website GEDMatch. The technology pointed to two second cousins of Talbott, which allowed investigators to construct a family tree and ultimately identify him as their primary suspect. 

Detectives used a discarded coffee cup to obtain Talbott’s DNA, which matched the evidence found at the crime scene.

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The case was the first time genetic genealogy had been used to put a suspect on trial, with prosecutors reportedly using Talbott as an example showcasing the power of genetic genealogy testing. 

“Folks aren’t going to get away with murder anymore when we have this information,” prosecutor Adam Cornell said, according to FOX 13. “If you’re a killer and you’re out there, then this office and other law enforcement around the country may be coming for you.”

Fox News Digital’s Michael Ruiz contributed to this report.