Nancy Guthrie missing: Forensic scientist encourages new investigative approach since case 'isn't cold yet'

TUCSON, Ariz. - One criminal expert said even though the investigation into Nancy Guthrie "isn't cold yet," the "best" forensic scientists should go into her house and "scrutinize" everything inside.

Forensic scientist Peter Valentin made the comments Friday on Fox News' "Crime and Justice" podcast with Donna Rotunno while discussing Nancy Guthrie's disappearance. Investigators continue to search for Nancy Guthrie as she has been missing for more than three weeks. Guthrie was forcibly taken from her Tucson, Arizona, home in the early morning hours of Feb. 1, Pima County Sheriff Chris Nanos previously said.

Fox News Digital previously reported that some DNA found in Nancy Guthrie's home came back to individuals with a reason to be there, two federal law enforcement sources said. DNA from a suspicious glove recovered two miles from Nancy Guthrie's home was also tested, but didn't match any of the samples from inside the home or any known criminals in the FBI's CODIS database.

Valentin, who's chair of the Forensic Science Department at the University of New Haven's Henry C. Lee College of Criminal Justice and Forensic Sciences, said on the "Crime and Justice" podcast that a fresh set of eyes might be needed.

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"What I would suggest is that you go into that house with the best people in each discipline in forensics," Valentin said. "Go into that house and scrutinize that house, looking for the trace evidence that must exist, or hopefully still exists."

The forensic expert is very confident that there is some type of evidence left behind by whatever individual is suspected to have taken Nancy Guthrie from her home.

"Because if people went into that home, and we believe they did, right? To take her from that house, there must be evidence of their presence in that home. Where is it? What is that evidence? We need to find it," he said.

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He also cautioned that the key piece of evidence that breaks the case might not be "obvious."

"It's not going be the obvious DNA profile somewhere, it is not going to be the obvious latent fingerprint. It's probably some of the things that we've probably not used as much, right? The hair, the fibers, the other kinds of trace evidence. But we've got to start cobbling together all the forensic evidence we have at our disposal to move this case forward, because otherwise it might not move forward," Valentin said. 

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Investigators got a fresh lead on Thursday when Fox News Digital exclusively reported that a resident in the Catalina Foothills neighborhood, about 2.5 miles from where Nancy Guthrie lives, has a Ring camera that captured 12 cars passing by on the morning of her suspected abduction. Some of the activity took place around 2:30 a.m., when authorities say the 84-year-old Guthrie's pacemaker device last synced with her iPhone.

In a new Instagram story posted on Friday, Savannah Guthrie pleaded with people to send in tips, and to "be the one who brings her home," referring to her mother, Nancy Guthrie.

Guthrie posted a segment from the "Today" show where viewers were shown how to submit tips anonymously. She said that tips can be anonymous "and likely paid in cash."

People with information about Nancy Guthrie's disappearance are asked to contact 1-800-CALL-FBI.