He said the sheriff had kept the FBI out of the investigation for the first four days and also criticized Nanos for sending DNA evidence to a lab in Florida instead of the FBI's lab in Quantico.
The Pima County Sheriff's Department responded to Patel's remarks in a statement on Tuesday night, saying a member of the FBI had been "promptly notified" by both the sheriff's department and the Guthrie family. The statement also said that decisions about the evidence were made "based on operational needs" and that the Florida lab and the FBI's lab "have worked in close partnership from the outset."
The disputes over the handling of the investigation could distract from efforts to solve the case. Nanos' work history and past conduct has also come under scrutiny amid criticism of seeming mishandling of the case.
Guthrie was last seen at her home outside Tucson, Arizona, on January 31 and reported missing on February 1. Authorities have said that she was taken against her will and that drops of her blood were found on her front porch.
Despite a massive search involving thousands of law enforcement officers and the FBI's assistance, there's been no sign of her since, and authorities have not identified a suspect or provided the public with details any major breakthroughs since the release of surveillance footage in February showing a masked man on her front porch.
On the podcast, Patel said the FBI was "kept out" of the investigation for four days, though he acknowledged that the case was in Nanos' jurisdiction.
"The first 48 hours of anyone's disappearance are the most critical," he said.
"And here's how these cases work. It is a state matter. It's a state and local law enforcement matter. What we, the FBI, do is say, 'Hey, we're here to help. What do you need? What can we do?' And for four days, we were kept out of the investigation."
Patel said when the FBI was brought in, it successfully managed to recover doorbell camera footage showing a masked individual on Guthrie’s porch on the night of her disappearance.
"That's why you have that image because the FBI worked with Google to put that image out," he said. "We could have gotten it days before. We could have also maybe gotten more data had we been let in earlier."
Patel also said that he had an aircraft on the ground ready to transport the DNA evidence to the FBI's lab.
"We said we'll take the DNA. And again, it's a state and local matter, so it's their call on where to send the DNA," he said.
"We have Quantico, best lab in the world. I had a fixed wing aircraft on the ground ready to move it immediately through the night... And they said we're sending it to Florida and and then I don't know."
Parel said the FBI's lab would have analyzed the DNA evidence within days and "maybe gotten better information or more information."
The Pima County Sheriff's Department said in a statement responding to Patel's comments: "Sheriff Nanos responded to the scene the night of the incident, providing immediate local leadership and oversight. A member of the FBI Task Force was also notified and present at that scene, working alongside our personnel. The FBI was promptly notified by both our department and the Guthrie family. While the FBI Director was not on scene, coordination with the Bureau began without delay."
The statement also said that decisions "regarding evidence processing were made on scene based on operational needs. The laboratory utilized by the Pima County Sheriff's Department and the FBI Laboratory in Quantico have worked in close partnership from the outset and continue to collaborate in the analysis of evidence."
It added: "We remain committed to a thorough, coordinated, and fact-based investigation and will continue working closely with our federal partners as the process moves forward."
It was reported last month that the FBI is now reviewing DNA evidence -- including a hair -- that was recovered from Guthrie's home that doesn't belong to her or those in close contact with her.
Nanos said in February that the DNA was "mixed," meaning it contains genetic material from more than one person, and that the private lab it was sent to had reported challenges with it, meaning it could be a while before it can be submitted for investigative genetic genealogy.
If the DNA is able to be submitted to a national database, it could help law enforcement identify a suspect and solve the case but it remains unknown if the DNA belongs to someone connected to Guthrie's disappearance.
An FBI spokesperson said last month that the FBI had "asked to test this DNA 2 months ago with the same technology we've always had -- when the local Sheriff instead sent it to a private lab. Any further developments we will share as soon as appropriate."
Nanos has come under pressure and faced calls to resign since The Arizona Republic reported in March that he misrepresented his work history on a public resume and in a sworn deposition. The report said Nanos had resigned in lieu of termination in 1982 after a string of disciplinary issues, two years earlier than he indicated on his publicly posted resume.
A spokesperson for the sheriff's department told Newsweek at the time that the discrepancies "were administrative in nature" and "not intended to mislead or misrepresent Sheriff Nanos' work history."
In March, a union representing more than 300 deputies in the sheriff's department called for Nanos to resign after passing a unanimous vote of no confidence.
Nanos addressed the calls for him to step down in an interview with News 4 Tucson. "For 50 years, every sheriff here has had that. I can't listen to that. That's white noise," he said.
He also defended his department's handling of the Guthrie case, saying: "You cannot attack my department -- attack the Sheriff, but you will not get by with attacking my department."
On April 21, Nanos sent a 22-page report to the Pima County Board of Supervisors, answering questions about his prior representations about his employment history with the El Paso Police Department, disciplinary actions, his department's cooperation with federal immigration authorities and instances of his department exceeding its budget.
The board will discuss Nanos' report at their next meeting on May 12.