Nancy Guthrie Case: Hair Found in Home Yields No Suspect as Labs Race to Untangle DNA Mixed From Four People

TUCSON, Ariz. — More than nine months after Nancy Guthrie was taken from her Arizona home, investigators are still pinning their hopes on a single complex DNA sample, after testing on hair recovered from the scene failed to point to a suspect.

Pima County Sheriff Chris Nanos told ABC News at the end of July that testing on the hair was complete. "The hair was done ... and there was nothing," he said.

Scientists weren't able to generate a DNA profile from the hair sample, Nanos told Fox News Digital at the time. Nanos said finding DNA on hair is "extremely rare," telling NBC News that hair doesn't produce DNA the way touch DNA or bodily fluids do.

That left a mixed DNA sample recovered from the home as the only known biological evidence in the case, and it has not been linked to a suspect.

A sample from as many as four people

The remaining evidence presents a difficult scientific challenge. The sample is a mixture from as many as four people, Nanos told ABC News, and it is not clear that the technology even exists yet to separate it.

A mixed sample makes standard database searches difficult. It contains genetic material from more than one person, which makes it nearly impossible to isolate a single profile and run it through national databases like CODIS.

Early testing was limited. Sources told Fox News Digital in February that the mixed DNA had so far provided only a partial profile, insufficient to check against CODIS.

Labs across the country

Multiple laboratories are working on the evidence, including the FBI lab in Quantico, Virginia, and labs in Kansas, Florida, California and Arizona, according to ABC News.

"My understanding is there are at least five, maybe six, labs across the country that are working on all of this," Nanos said in July.

More recently, the sheriff described the work in similar terms. Nanos said in a radio interview that evidence has gone to four specialized labs, including facilities in Florida, Kansas and San Francisco, and investigators recently traveled to Florida to meet with a lab analyzing the mixed DNA.

Reports say one lab is working to separate a DNA mixture from multiple people, while another specializes in difficult samples such as a hair without a root.

Authorities have not announced a breakthrough from the testing.

What experts say

Forensic experts say new methods could eventually help. CeCe Moore, chief genetic genealogist at Parabon NanoLabs, has said it is possible to deconvolute a mixed sample and get a profile, but it is very hard to get one into CODIS.

Moore has also suggested another path. If investigators have found only a complex mixture at the residence, she said, "my hope is that they will discover a second crime scene," such as a place where Guthrie was held or a car used to transport her.

One suspect or several?

Investigators believe Guthrie, 84, was taken from her Tucson-area home in the early hours of Feb. 1 by a masked man seen on her doorbell camera. But Nanos has not ruled out that others were involved.

"Did he have help? Could have," Nanos told ABC News.

'This case is not cold'

Despite the setbacks, Nanos has insisted the investigation remains active. "This case is not cold," he has said.

He has also appealed directly to the public. "Somebody knows where Nancy's at. We need their help," Nanos said, urging anyone with information to come forward.

Nanos has praised Savannah Guthrie, the "Today" show co-anchor and Nancy's daughter, for keeping the case in the public eye through her social media posts.

Other leads ruled out

Two discoveries of human remains in the Tucson area drew attention, but neither has been linked to her case.

Reward

The Guthrie family is offering a $1 million reward, and the FBI is offering up to $100,000.

Anyone with information is asked to contact the FBI at 1-800-CALL-FBI or the Pima County Sheriff's Department.