The chief detective leading the hunt for missing Nancy Guthrie was once fired for beating a wounded, handcuffed suspect with the butt of his gun, the Daily Mail can reveal.

Joseph Cameron, now the top investigator within the Pima County Sheriff's Department in Arizona, admitted using his weapon to bash the man who had already  been shot by another officer.

He also confessed he later slapped the shackled suspect to try to get him to incriminate himself.

At the time, Cameron was a sheriff's deputy called Joseph Harvey, and was subsequently fired by then Sheriff Clarence Dupnik in 2001 for using excessive force and poor judgment.

But he won his job back after a lengthy process that eventually went to the Arizona Supreme Court – which upheld a 2003 decision to allow him to return and make his way up the career ladder.

The revelation follows more stunning alleged details about under-fire Pima County Sheriff Chris Nanos. 

These include eight alleged suspensions while a young officer in El Paso, Texas, and claims he also beat a handcuffed suspect while a young officer.

And in a separate development late Tuesday, Nanos admitted to Pima County Board of Supervisors in an attorney's letter that he quit the El Paso job to avoid a three-day suspension for insubordination in 1982.

His testimony in the 22-page document follows long-running accusations that he misrepresented his work history to Pima County officials.

In the case of Nanos's now detective chief, the state Supreme Court's ruling opinion over his job fight included the background: 'Deputy Harvey testified in a criminal case that to effectuate an arrest, he had hit the arrestee with the butt of his gun and later slapped the handcuffed, shackled and wounded man.

'After reviewing the testimony and other reports of the incident, Pima County Sheriff Clarence Dupnik concluded that Deputy Harvey had used excessive force, engaged in inappropriate interview techniques and showed poor judgment'.

The filing said the termination notice from Dupnik cited the arrest incident and also alleged 'other rule and policy infractions'.

Quoting from the notice, these included the cop's 'career-long pattern of failure and/or unwillingness to comply with department rules and regulations'.

The judges said there was also 'disregard of commands from a fellow officer, his absence without leave to drive an intoxicated friend home, and his inclusion of false information on booking forms'.

The fired cop appealed his termination to Pima County Law Enforcement Merit System Council, the ruling body for personnel administration.

He testified before a hearing officer that he'd slapped the suspect to revive him, not just to get incriminating details. Colleagues who saw the incident backed him up.

'Some law enforcement officers, however, testified that slapping a suspect is not an acceptable way to render first aid,' the supreme court stated.

'Harvey did not deny the other accusations of misconduct, but minimized them. He questioned the timing of his termination, which occurred nearly eighteen months after the incident with the arrestee.'

The council's hearing officer accepted the cop's version of events over the suspect and found there was no case for discipline. He was rapped on the knuckles for the other infractions.

Pima County and Sheriff Dupnik then began a legal back and forth through Arizona courts that resulted in the Supreme Court declaring the merit system council was correct to overrule the sheriff.

By that time Joseph Harvey had changed his name to Joseph Cameron and had began working as a deputy again two years after his firing. 

Now – as the sheriff's department faces allegations of incompetence over Guthrie under Sheriff Nanos's leadership – Cameron's title is investigations bureau chief.

And as the hunt for the mother of NBC Today show host Savannah Guthrie approaches three months, that fact is itself creating controversy within the sheriff's department, we can reveal.

'Cameron is the chief of detectives and he's had the job for a year. But he was never a detective before that. Never. Not once,' a senior department source revealed to the Daily Mail.

'Somehow he's now in charge of the section in the middle of a high-profile case that appears to be going nowhere and still has the world watching.

'Everyone views him as Nanos's muscle. He's his driver for most events. No one thinks he got his position through competency. He's a long-time sheriff's department hardman.

'His appointment feeds into the narrative that Nanos rewards people based on loyalty, not competency.'

The Pima County Sheriff’s Department said 'there is no further information to share’ regarding Cameron when asked for a comment. 

Nancy was snatched from her $1million home in the affluent Catalina Foothills area of Tucson in the early hours of February 1.

A sinister masked and armed man captured on her door camera remains the investigation's biggest focus amid a $1million reward offer by TV star Savannah and her family.

Roughly six Pima County detectives are still working out of the Tucson FBI office in a joint operation. After criticism of their lack of experience, a 12-year detective veteran has now joined them, we can reveal.

'Cameron would be read in on pretty much everything to do with the case, although I don't know if he's offering any direction,' said our source. 'But with his position, if he tells detectives to do something, they'll have to do it.'

Before leading the detective unit, Cameron was in charge of internal affairs 'which was a curious choice to say the least and some felt an insult,' added the insider.

'He got fired as Joe Harvey and came back as Joe Cameron, I think as a way to shake the negative connotations with his last name.'