On the morning of Feb. 1,Nancy Guthriewas expected at a friend's home in Tucson, Arizona, to watch a livestreamed church service, as she did most Sundays.
But when the 84-year-old mother of "TODAY" co-host Savannah Guthrie never showed up, those friends alerted her children — spurring a missing person investigation that remains unresolved three weeks later.
The ongoing investigation into the disappearance of Guthrie, who was last seen around 9:45 p.m. Jan. 31 after having dinner with her family, now involves local, state and federal law enforcement agencies and has garnered international attention. All members of the Guthrie family — including her three children, who havemade pleas onlinefor her return and have said they are willing to pay to get her back, and their spouses —have been cleared as potential suspects in the case, according to Pima County Sheriff Chris Nanos.
While authorities believe Guthrie was possibly taken from her home, no suspects or persons of interest have been publicly identified. DNA from her home does not match any samples in an FBI database, and authorities are still asking for the public's help to identify a man seen in images and videos captured byGuthrie's doorbell camera the morning she disappeared.
Investigators, however, have said the suspect's gun, its unique holster and a backpack — which is exclusively sold at Walmart — could be the best clues and best ways to find answers.
In an interview with NBC News on Sunday, Nanos said authorities are getting closer to identifying the other articles of clothing seen in the doorbell camera video, including shoes, pants, shirt and jacket.
While updates in the investigation have slowed, experts told NBC News that officials still have plenty of avenues to pursue as the search stretches into its fourth week.
Identifying a suspect through forensic genetic genealogy
Investigators have identified multiple sources of DNA in and around the crime scene, but testing has yielded no results, leading them to take deeper steps to move the case forward.
A glove was found 2 miles from Guthrie's home that appeared to match the pair that the man in the doorbell video was wearing. The Pima County Sheriff's Department, however, revealed that the DNA found on the glove did not matchany DNAin the Combined DNA Index System (CODIS), which has 19 million offender DNA profiles nationally and more than 1 million forensic profiles. From Arizona alone, there are more than 434,000 offender profiles in CODIS, according to the FBI.
Officials say they are nowtesting DNA found at Guthrie's home— which did not match her or anyone who was known to be there recently —through a process called forensic genetic genealogyin the hopes of identifying a suspect. The DNA sample is mixed, Nanos said, meaning it contains genetic information from at least two people and could take longer to test.
"We believe that we may have some DNA there that may be our suspect, but we won't know that until that DNA is separated, sorted out, maybe admitted to CODIS, maybe through genetic genealogy," he said.
Dr. David Mittelman, a genetic genealogist and CEO of Othram Inc., explained that this process takes DNA — usually found at crime scenes — and first converts it into code. Then it is entered into a database containing DNA samples from a few million people and 500,000 genetic markers.
From that data, the system creates a family tree based on that person's DNA markers, matching the unknown suspect with potential relatives to narrow down who investigators may be looking for.
While the match is not always exact, Mittelman said that at the very least it will point officials to a close relative of the person whose DNA was tested, narrowing down the suspect pool in a major way. He said this is called an "identity hypothesis."
"So in the worst-case scenario, it'll connect you to a very close relative, and the best-case scenario gets it to your person," he said.
Then, it's up to investigators to identify and question that person to determine whether they are a true suspect.
Mittelman added that it is imperative that investigators carefully obtain enough DNA from the scene and emphasized the importance of working fast to identify a subject early in an investigation.
Othram often works with law enforcement agencies to help solve crimes, including creating the profile forBryan Kohberger, the man who slaughtered four University of Idaho students in 2022. Mittelman declined to comment on whether Othram is working with law enforcement on the Guthrie case.
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CeCe Moore, a genetic genealogy expert, said that the process could take from hours to months to complete, but that when results do come in, they will be conclusive. She added that she is "extremely hopeful" that this process will identify a suspect.
"If I was the kidnapper, I would be extremely concerned right now, because using investigative genetic genealogy, he will be identified. It's just a matter of time," she said.
Following leads and listening to the public
Nanos on Sunday characterized the investigation as expanding rather than shrinking, with detectives continuing to process evidence.
The intense public interest in Guthrie's disappearance has helped spur an influx of tips to investigators.
The Pima County Sheriff's Department and theFBI say they have received tens of thousands of public leadssince Guthrie went missing. The FBI is offering a $100,000 reward for any information that leads to Guthrie or to the arrest of those who took her, andan additional $102,500 rewardis being offered through Tucson Crime Stoppers, known locally as 88-CRIME.
Investigators have said they are already following leads based on gathered evidence, including working with Walmart to identify who may have purchased the backpack seen with the man in the doorbell video.
They have also been trying to track the gun the man was carrying. Firearms expert John Correia said it appeared to be held in a universal fit holster and isn't one an experienced gun owner would use.
Chris Burbank, a former police chief in Salt Lake City, said that if he were investigating the case, he would also allocate resources to investigate unverified ransom notes that have apparently been sent to multiple news outlets. NBC News has not independently verified these ransom notes, and law enforcement has not said whether they are legitimate.
He also said investigators can use artificial intelligence to track any social media leads because "most of the time, people involved in this leave some sort of social media trail."
"We've gathered all the physical evidence, we've done all that I can think of at the scene in the area, now it's time — let's really start combing every other bit of information that exists out there in the world," Burbank said.
The investigation remains far from going cold
Three law enforcement experts who spoke to NBC News all emphasized that while investigators have not made an arrest or found Guthrie, the case is far from going cold.
"I would be really surprised if a case this high-profile gets shelved before six months, a year," Burbank said.
All agreed that officials never want a case to go cold, because the longer the investigation remains active, the more news coverage it will garner, leading to continued attention on the case and, therefore, continued tips and assistance from the public.
A case is considered cold only when all available leads have dried up, and there is no further evidence to analyze. Considering the thousands of leads still available in the Guthrie case, it is not at an immediate risk of being put on the back burner.
At some point, though, once investigators have ruled out all possible suspects, "you're going to start putting your resources elsewhere, because there are other cases that you have a higher percentage of solving," Burbank said.
Anne E Schwartz, a law enforcement communications expert and former journalist who first reported on serial killer Jeffrey Dahmer's case, added that the public may see "a small, gradual drawdown of resources" once investigators have cleared all leads.
Burbank noted that high-profile cases such as this one will never go 100% cold because there will always be a detective dedicated to fielding calls and resources working in the background to continue solving it.
Last week, Nanos suggested something similar.
"As long as we have the ability to chase a lead, it's not cold," he said. "We're not going to give up. We're going to find Nancy, and we're going to find out who did this."