Queensland police failed to carry out an impartial or thorough investigation into the disappearance of one of their own officers, a court heard today.

The District Court in Brisbane was also told a senior QPS officer manipulated a corruption investigation into the officer, who went missing shortly after being cleared of the allegations.

Senior Sergeant Mick Isles disappeared in September 2009 after leaving his home in Ayr in north Queensland to go on a routine work trip.

The state coroner later found he had committed suicide although his body has never been found.

His son Steven Isles today made an application in the District Court for the suicide verdict to be set aside in favour of an open verdict.

He told the court the basis for the verdict was "flimsy" and cited new evidence allegedly pointing to corrupt behaviour on the part of senior police as well as bullying and cronyism, and a failure to "exhaust all avenues" in the investigation.

"If my father's death involved foul play, it certainly would have involved other police officers," he told the court.

In an impassioned address, Mr Isles told the court the family was not averse to a finding of suicide but said his father's disappearance would stay a mystery in the absence of "remains or other evidence".

He pointed out to the court that despite the suicide verdict, his father remained on the missing persons register of the Australian Federal Police.

He also called for an independent commission of inquiry into the disappearance, but Judge Douglas McGill said that was a matter for the Queensland Attorney General.

Undated letter not likely a suicide note: son

Mr Isles said an undated note his mother had found in a wardrobe, construed as a suicide note by the coroner, was not left out to be found and was more likely written months earlier when Mick Isles was battling cancer, from which he later recovered.

Mr Isles played the court an audio recording of a witness describing having seen a car on the morning of Mick Isles' disappearance that exactly matched the one the officer had been driving, but with two smartly dressed men in it.

In the recording, grazier Graham Spurdle said young police officers who interviewed him at the time had told him the timing of his sighting matched up with earlier CCTV footage of Mick Isles' vehicle, but older officers "didn't seem interested".

Mr Isles also claimed there had been "a deficit of impartiality" on the part of police investigators into the disappearance.

He said the only person interviewed about his father's disappearance had been him and that he was later falsely accused by Queensland police officers of making threats to the then-police commissioner, Bob Atkinson.

The court heard that within 36 hours of his father's disappearance, a police superintendent allegedly told Steven Isles: "Don't speak to the media and your mother will never suffer financial pressures."

Assistant Commissioner 'manipulated' corruption investigation

Mick Isles was investigated by Queensland's corruption watchdog, the Crime and Misconduct Commission (CMC), over allegations of taking cash bribes in exchange for driving licences.

He was referred to the CMC by the regional police commander, Assistant Commissioner Paul Wilson, in July 2008, after a local drug dealer, Sam Galeano, was allegedly caught on a surveillance recording discussing cash payments to police officers with another person who became a "person of interest" in the CMC probe.

Steven Isles told the court this year he had obtained evidence that Mr Wilson had been in contact with the "person of interest" just prior to search warrants being executed on the Isles' family home in August 2008.

Former Assistant Commissioner Paul Wilson in 2011. ( AAP: Tony Bartlett )

He said Mr Wilson had "omitted every step of the way" to mention this contact, despite a parliamentary review of the CMC investigation in 2009 and the 2012 inquest.

Mr Isles claims in an affidavit in support of his application that had Mr Wilson disclosed the contact it "would have been a game changer to the application for the search warrants, and would have drastically altered the direction of the CMC investigation".

Mr Isles alleged in the hearing that Mr Wilson wanted Mick Isles replaced as officer in charge of the Ayr police station by another officer with whom Mr Wilson was personally connected.

Mr Wilson went on to become chief of police on the Gold Coast.

He left the QPS in 2014 with a CMC finding of misconduct against him for disclosing information that led to the identification of a Crime Stoppers informant.

Mr Wilson was not in court to give evidence and it is not being suggested he had anything to do with Mick Isles' disappearance.

Lawyer Terry O'Gorman helped the family after Mick Isles went missing.

He told the ABC: "If this new information had been before the coroner when he was inquiring into the disappearance of Sergeant Isles it may have led the coroner to conclude that he would have to conduct investigations in a different direction and it may have had an influence on the outcome and the coroner's finding."

The District Court has reserved its judgment in the application.