Five detectives, including senior Major Crime investigators, have been stood aside from duty and another four officers face disciplinary action over the botched Josh Warneke murder investigation.
Police Commissioner Karl O'Callaghan took action against the five officers on Friday – almost a year after he ordered the Internal Affairs Unit to investigate the conduct of police involved in the long-running homicide probe.
"Managerial action" is being considered against four additional officers.
It is understood Detective Superintendent Anthony Lee, the head of the Major Crime Division, and lead case investigator Detective Senior Sergeant Cameron Western are among the officers under scrutiny.
After questioning from Fairfax Media, a WA Police spokeswoman confirmed: "Five officers have been stood aside from their current roles in WA Police but remain on duty."
"A further four officers are being considered for managerial action," she said.
"No decision has been made in relation to the outcome of the internal investigation process.
"It remains a matter for the Police Commissioner to consider what further action will follow."
The police spokeswoman declined to name the officers involved.
The inquiry came after a court raised concerns in July last year about the reliability of police interviews by Major Crime detectives, in which Gene Gibson, 23, allegedly confessed to running over Mr Warneke and hitting the 21-year-old with a rock.
Supreme Court Justice Stephen Hall threw the interviews out of court, saying breaches of the Criminal Investigation Act and the conduct of police had cast significant doubt about the reliability of the evidence.
Justice Hall found the police officers involved in the two-year investigation had committed several breaches of the Criminal Investigation Act, including conducting police interviews with Gibson on August 16 and 17, 2012 that were "not voluntary".
It was revealed in court that police had not followed due process in conducting the interviews, including failing to appropriately caution Gibson, who lived in the remote Aboriginal community of Kiwirrkurra in the Gibson Desert, not offering an interpreter despite the suspect's "limited English" and by failing to record the interview from the outset.
The murder charge was subsequently dropped and Gibson pleaded guilty to the lesser charge of manslaughter.
Mr Warneke was found dead by a passing taxi driver on the side of Old Broome Rd at 3am after a night out with friends on February 26, 2010. He had sustained massive head injuries.
In October, Gibson was sentenced to 7 ½ years jail over Mr Warneke's murder. He will be eligible for parole after serving 5 ½ years.
The court heard Gibson was "grossly intoxicated" and had been smoking cannabis before he attacked Mr Warneke, hitting him in the back of the head with a metal pole before leaving him by the side of Old Broome Road with fatal head injuries.
In sentencing, Justice Lindy Jenkins said the attack was unprovoked and Mr Warneke did nothing to justify the "cowardly act".
In July, Mr Warneke's mother, Ingrid Bishop, expressed disbelief that the man who killed her only son would escape a murder charge after police failed to follow due process when interviewing the suspect.
Ms Bishop, who initially praised the police work when charges were laid against Gibson in August 2012, said she felt "hood-winked".
"We shouldn't be in this situation and if due process had been followed I think there would have been a very different outcome," she said.
"We can't change anything. Josh lost his life and his future. Such a beautiful soul is lost and now it's become a political process built around incompetence."
Ms Bishop has been contacted for comment about the officers stood aside.
