TUCSON, Ariz. — Q tip, tissue and pizza crust.
For investigators, this seemingly innocent trash is a treasure trove of DNA, helping to solve the University of Idaho murders, the Golden State Killer and the Gilgo Beach murders, according to authorities, using a research tool called Investigative genetic genealogy.
Investigators in the Nancy Guthrie case are hoping science can identify a suspect. But there are challenges.
Guthrie, 84, the mother of Savannah Guthrie, who was with him on the “TODAY” show, was reported missing on Feb. 1. It’s been three painful weeks since she disappeared, and authorities have yet to publicly identify a suspect or person of interest. Officials have eliminated the Guthrie family as suspects, Pima County Sheriff Chris Nanos said.
Nanos, whose agency is leading the investigation along with federal and state partners, said last week that mixed and partial DNA was found at Guthrie’s home. Mixed DNA is a forensic sample that contains more than one person’s genetic makeup.
Also mentioned is the disappearance of Nancy Guthrie
Some of the DNA found at the home did not belong to Guthrie, his family or anyone who worked at the property, Nanos said.
“We believe we may have DNA there that may be our suspect, but we won’t know until that DNA is separated, sorted, maybe accepted into CODIS, maybe through genealogy,” Nanos said Tuesday, referring to the Combined DNA Index System. the FBI’s DNA database of convicted felons.
But on Friday, he told NBC News that the lab that obtained the DNA reported “challenges” with the sample. He did not elaborate on what the challenges were.
“We listen to our lab, and our lab tells us that there are challenges with it, and we understand those challenges, but our lab also knows that technology is moving so fast and so fast that they think that some of these things will be solved in a few weeks, months or maybe a year, to allow them to do better, like, a mix of that kind of thing,” he said.
Nanos he said he is “hopeful” that samples will get to the point where they can be submitted to genealogy investigators or entered into CODIS, but “we’re not there yet.”
The sheriff’s department said in a statement Saturday: “As with any biological evidence, there may be challenges separating DNA, etc. There are currently no updates on this process.”
Investigative genetic genealogy, or IGG for short, is a process in which unknown DNA evidence is converted into a digital DNA profile. Then it’s into the archives of ancestors to find relatives, build family trees and narrow down the person behind the DNA. It is used to solve cold cases, identify unknown victims and murderers.
The issue Nanos identified could be from the DNA sample itself or from the genealogy process, said Barbara Rae-Venter, a geneticist who helped solve the Golden State Killer case in 2018 using this method.
He said the sheriff’s comments indicate that the DNA test has a very high amount of DNA from the victims.
Colleen Fitzpatrick, an American geneticist, said that when it comes to mixed DNA, the suspect should be the one who played a major role.
“Let’s say you have a mixture and 90% is Nancy’s and 10% is someone else’s, that may not be enough for the lab to go ahead and find enough markers and make an identification,” said Fitzpatrick. “If it’s 50-50, it’s hard to split. Ninety-10, you can split that. And maybe the question isn’t just split, do you have enough DNA to work with?”
The lab that authorities are believed to be using in Guthrie’s case did not respond to a request for comment.
IGG challenges Guthrie’s case
There are several challenges that investigators and geneticists may face in this case.
But mixed DNA, often found at crime scenes, can still yield useful information, according to CeCe Moore, a senior geneticist at Parabon, a Virginia-based genealogy lab.
“We have had success with many mixed cases,” he said. “But it takes a little more time, because there’s an extra step. After that profile is created that requires a genealogy, they have to have bioinformatics scientists work on that file to extract the suspect’s DNA.”
Moore said the discovery of mixed DNA makes him “hopeful,” because “that seems like a possible connection to the kidnapper in this case.”
Earlier, Nanos said blood was found on the porch outside Guthrie’s home that was found to have his DNA.
It takes about a day or two to build a DNA profile — and then “there are leads immediately,” says David Mittelman, a genealogist and CEO of Othram, a forensics laboratory in Texas.
“In the worst case, it will connect you with a very close relative, and the best case is getting it from your person,” he said.
The IGG can also provide other information such as biogeographical ancestry, which means where the person came from historically, and connect them to larger families in certain parts of the country, Mittelman said.
Moore says the speed of achieving success through this process depends on race and lineage.
“If the person of interest, in this case, has deep roots in the US and is a white person, they can be identified in minutes or hours,” Moore said. “Most of the people in the information we have access to have northwest European ancestry and deep roots in the United States.”
But he said there is very little representation in the database of those with recent immigrant ancestors or those born outside the US.
“If it’s someone who doesn’t have a connection to the US in their tree in later generations, it can take a long time,” Moore said.
This was the case with the identification of Bryan Kohberger, who killed four students at the University of Idaho in 2022. It took a few weeks because he had recent Italian ancestors.
Achieving the record is also a challenge for other races, including African Americans.
“You’re bricked when you’re free,” Rae-Venter said. “The actual written records of those marriages and deaths, which is what we usually use when we try to build these trees, there are no records once you hit the wall of slavery. You can’t go back to 1863.”
Access to the database
Then there is the issue of how many gene gene profiles to compare.
They’re limited to fewer than 2 million profiles to sift through — even though more than 50 million people have tested DNA specific to consumers, Moore said.
That’s because big companies like Ancestry DNA and 23andMe, popular ancestry tracing sites, have blocked law enforcement from accessing their databases to protect users’ privacy. However, those records can be subpoenaed by law enforcement and those companies can be compelled by court order or search warrant. Databases they can use are GEDMatch and FamilyTreeDNA, which have logging capabilities that allow law enforcement to compare profiles.
“The two databases we’re allowed to use are two very small databases. If we could use Ancestry or 23andMe or MyHeritage, those databases are huge. You’re talking about 10, 20 times more people,” Rae-Venter said.
“When you’re working on something like the Kohberger case or the Nancy Guthrie case, immediately time is of the essence. … We’re adding time to what was already a time-consuming process,” he said of the database’s limitations.
Although DNA samples from Guthrie’s case are not yet visible, experts have high hopes.
Rae-Venter said the IGG has been around since 2007, back when it was mostly used in unknown parental cases.
One of the first uses in the criminal case was the arrest of the Golden State Killer, Joseph James DeAngelo, in 2018. In 2020, he was sentenced to life in prison without parole after pleading guilty to 13 counts of murder and 13 counts of rape.
“Back when we were doing Golden State Killer, there were almost no tools to analyze the game information you were getting, and now there are all kinds of really sophisticated tools to do that,” Rae-Venter said.
One of the advances is the ability to work with small amounts of DNA.
“Back when we did that, you needed about 200 nanograms of DNA. Now, I actually made the case, I think we had 25 images, so it was less than 1,000 DNA,” he said.
He hopes that if enough DNA is collected, it can solve Guthrie’s case.
“If they think they have been able to extract a decent DNA sample, they should be able to identify a possible suspect. The question is how long it will take,” he said. “But in the end, you should be able to solve this case.”
Marlene Lenthang reported from Los Angeles and Erin McLaughlin and Liz Kreutz from Tucson.
