This isn't the Sheriff's first high profile, public case. Back in 2011, he was the Criminal Investigations Division Captain during the investigation for congresswoman Gabby Gifford's shooting to her head.
But, it appears he's decided not to work WITH the FBI on the Nancy Guthrie case.
According to Reuters on last Thursday, (11 days into the case):
"Arizona sheriff blocks FBI access to evidence in Nancy Guthrie abduction, source says"
WASHINGTON, Feb 12 (Reuters) - An Arizona sheriff is blocking FBI access to key evidence in the investigation into the abduction of U.S. television journalist Savannah Guthrie's mother, impairing its ability to assist in the probe, a U.S. law enforcement official with knowledge of the case told Reuters on Thursday.
The FBI asked Pima County Sheriff Chris Nanos for physical evidence in the case, including a glove and DNA from the home of 84-year-old Nancy Guthrie, to be processed at the FBI's national crime laboratory in Quantico, Virginia, but Nanos has insisted instead on using a private lab in Florida, the official said.
Nanos did not respond to requests for comment from Reuters. But in an interview with Tucson television station KVOA late on Thursday, he said the FBI agreed with his decision to send newly discovered evidence to the lab, which has worked with his office for years.
The U.S. law enforcement official said outsourcing forensic analysis to a Florida contractor, effectively denying the access of the Federal Bureau of Investigation to crucial evidence in the case, is delaying the FBI's ability to assist in the case."
A county has primary jurisdiction over the case and FBI assistance must be officially requested by the county, the family or if the crime crosses state lines, which then makes it a federal crime and it becomes the FBI's case.
The first few days, the Sheriff may have considered it a local abduction, and even when he realized it was a very high profile case, being as it's Savannah's mother, he didn't call in the FBI.
However, when it became clear to Savannah that the Sheriff was suspecting her BIL or other family, by not properly securing the crime scene down and instead searched her sister & BIL's home TWICE, she may have asked the FBI in on the investigation and to work with her.
And/or when what seemed like a credible ransom note was sent to TMZ headquarters in California, that possibly turned it into an FBI case. TMZ did confirm they got calls from the FBI about the notes they received and have been cooperating.
Most telling is an interview where the Sheriff ADMITS he didn't even KNOW ahead of time that Savannah & her siblings made their first public plea directly to the kidnappers, with the FBI's help and probable coaching on what to say. His WIFE shared it with him on Facebook after she saw it. Savannah's not working with, or it seems even talking to the Sheriff as to what she and the family are doing. She's working with the FBI who has worked on thousands of abductions.
The very fact that the Sheriff said the investigation could take years means he clearly thinks Nancy is dead and this is now a recovery for her body and arrest of the kidnappers, whenever that may possibly be.

So, he's already working differently than he would if he still thought it may be viable to get Nancy back alive. Or get the kidnappers soon.