As the FBI continues searching for kidnapped 84-year-old Nancy Guthrie in the United States, a former FBI negotiator says they will be focusing on the grandmother's social circle and family.
"[They would be] family members, spouses of family members, friends, cleaning ladies, yard people, anybody that had some kind of connection, personal connection," Dr Nancy Zarse, a former FBI consultant and hostage negotiator, told 7.30.
"I'm not suggesting it's the family, but … this doesn't feel random to me."
The case has gripped the world, with purported ransom notes, doorbell camera footage and a black glove all coming to light.
At the centre of it all is Today show co-host Savannah Guthrie.
The NBC star's mother, Nancy, was last seen at her Tucson, Arizona home on January 31.
She had been visiting daughter Annie Guthrie's house six kilometres away before she was driven to her home by her son-in-law, Tommaso Cioni.
The FBI has searched Annie and Tommaso's house multiple times as part of their inquiries. They have not been named as suspects or persons of interest.
Dr Zarse believes Nancy Guthrie is still alive and that, while things have been quiet, there may have been some communication with anyone holding her hostage.
"They're still pretty actively searching for Nancy Guthrie. So I think there are ongoing negotiations and I think the kidnappers are providing proof of life," she said.
'Savannah is the deep pocket'
In her experience working with the FBI and as a forensic psychologist, Dr Zarse says choosing to kidnap Nancy Guthrie "doesn't make intuitive sense".
As one of NBC's top on-air talents, it is well known that Savannah Guthrie has a multi-million-dollar contract with the network.
Her mother has also appeared on the Today show with her.
"It just feels like a really odd target and a really unique case in America," Dr Zarse said.
"On the surface, it would make more sense to kidnap Savannah Guthrie than it would to kidnap the mother of Savannah Guthrie because there's no indication that the mother is an equally high-value net worth person.
"Savannah Guthrie is the deep pocket here."
Dr Zarse told 7.30 those deep pockets and the desire to get Nancy back could lead to what she believes is a mistake from Savannah — who has indicated a willingness to pay a ransom — even though the FBI has not confirmed the legitimacy of any ransom notes.
"The FBI does not advise that you pay ransoms for several reasons," she said.
"One, if you say you're going to, the kidnappers might increase the price, thinking that you're going to pay more. Number two, kidnapping ransoms can be used to fund other criminal behaviour. Three, paying here might prompt a copycat crime."
Black glove, vast desert
The FBI has two key pieces of the investigation they now believe are linked.
Last week, three kilometres from Nancy Guthrie's house, investigators found a black glove that appears to match those worn by the masked man. The DNA on that glove is being tested.
"That DNA evidence is currently at the FBI lab at Quantico, which obviously has the most sophisticated, fastest DNA matching ability in the world," former special FBI agent Rob Chadwick told 7.30.
Mr Chadwick says investigators don't need to make an exact DNA match with a suspect to have a breakthrough.
"The genealogy programmes and recent practises in the United States, and I'm sure internationally, DNA swabbing has been going on for quite some time now," he said.
"So we've really built up quite a database to look at maybe even familial relations, so this will help us really narrow the scope tremendously in terms of trying to identify a suspect."
While the glove may provide some clues, retired homicide detective Gil Carrillo says investigators need to be searching for clues beyond Arizona.
Mr Carrillo solved the infamous 80s Night Stalker serial killer case. The breakthrough came from the suspect's distinctive shoe print left at crime scenes.
"You have a great big desert out there, so there's 1,001 places to hide to keep her secreted someplace," Mr Carillo said.
"There's places to dump evidence, whatever evidence there be. And you have the Mexican border right there."
Since Nancy Guthrie went missing on February 1, her children, Savannah, Camron and Annie, have been making public pleas directly to those responsible.
On Monday, Savannah posted a desperate video urging them to give themselves up.
"To whoever has her or knows where she is … it is never too late to do the right thing," she said.
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