DNA recovered from inside Nancy Guthrie's house may not provide enough evidence to help investigators identify the people behind the disappearance of the mother of "Today" show co-host Savannah Guthrie.
According to sources close to the investigation, there are concerns that DNA recovered from Nancy Guthrie's Tucson, Arizona, home may not yield a usable profile for comparison in federal and private sector DNA databases. One source called the recovered DNA "low-level."
Another law enforcement source said that a low-level sample would likely mean there was not enough DNA material present to get a clean and reliable result. However, they said, even a low-level sample can be enhanced by scientific techniques in the lab but would take longer to achieve.
The Pima County Sheriff's Department said its contracted lab in Florida is continuing to analyze the samples and has not reached a conclusion on whether they're usable.
With the investigation into Guthrie's disappearance now in its fourth week, authorities haven't named a suspect or a person of interest in the case. Last week, Pima County Sheriff Chris Nanos said in a statement that all of Nancy Guthrie's three adult children and their spouses were cleared as possible suspects in the case.
Earlier Tuesday, Savannah Guthrie announced that her family was offering a reward of up to $1 million for information leading to her return. The FBI also separately announced a $100,000 reward.
A DNA profile from a set of gloves found about 2 miles from Guthrie's house didn't match any entries in the national database maintained by the FBI known as the Combined DNA Index System, or CoDIS, the sheriff's department said. The database contains DNA profiles of individuals with a previous arrest for certain crimes who had supplied a DNA sample.
Authorities have turned to an investigative technique called genetic genealogy as they try to make the most of the DNA evidence. The process has been used to crack some notable cases in the past decade, including identifying the so-called Golden State Killer in California who'd eluded authorities for over 40 years and the man behind the high-profile killings of four Idaho college students.
The method involves using publicly available genealogy sites to find genetic relatives of an unidentified DNA sample that may belong to a potential suspect.
Claire Glynn, the director of the graduate-level program in forensic investigative genetic genealogy at the University of New Haven in Connecticut, told CBS News that law enforcement agencies are generally allowed to use two databases for such investigations, GEDmatch Pro and FamilyTreeDNA.
FamilyTreeDNA recently told CBS News that the company doesn't work directly with authorities on genetic genealogy cases, but instead conducts such work through an independent third-party partner that uses a separate consent-based database.
"Participation in investigative genetic genealogy matching at FamilyTreeDNA is strictly voluntary and opt-in only," the company said. "We place the highest priority on customer privacy, data security, and ethical use in all aspects of our operations."
GEDmatch PRO told CBS News that law enforcement agencies use its database to identify criminals as well as human remains. Tom Osypian, an official at the company, said in a statement that it's a self-serve platform so the company often doesn't get contacted when authorities upload DNA profiles to its database.
"In fact, we don't usually find out that our service was used to solve a case until we learn about it from a press announcement from law enforcement," Osypian said.
Other publicly available DNA submission sites don't allow law enforcement agencies to use their services as freely without going through the legal process.
Grace Samuelson and Alex Sundby contributed to this report.
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