Police officers whose behaviour was described as ranging from "inappropriate to reprehensible" by Lloyd Rayney's trial judge have been cleared of any serious misconduct.
The Corruption and Crime Commission confirmed yesterday it had finished investigating three officers over two matters.
While no misconduct was identified in either, one officer was found to have acted "unreasonably" but will face no punishment.
It has been 18 months since Mr Rayney was found not guilty of killing his wife Corryn.
At the trial, Justice Brian Martin was scathing of the conduct of several senior investigators, including two detectives accused of threatening a female lawyer and colleague of Mr Rayney in an attempt to secure her co-operation.
It was claimed during the trial the officers said to Clare O'Brien: "You know how it works Clare. We charge you, you lose your job, you can't get a lawyer because you have no money, we then drop the charges and you are yesterday's news."
The CCC made no adverse findings against those two detectives.
The other matter the CCC reviewed related to attempts by a third officer to encourage an independent pathologist involved in the case to change a report to better fit police evidence.
That officer was found to have acted unreasonably.
"I accept the CCC's interpretation and don't intend to take any further action," Police Commissioner Karl O'Callaghan said.
Justice Martin criticised several other officers involved in the case, including then Det. Sen-Sgt Jack Lee, who described Mr Rayney at a press conference as the "prime suspect".
The CCC initially reviewed that matter but did consider it worthy of further investigation.
"There are no further inquiries under way and no findings pending," a spokeswoman said.
WA Police Union president George Tilbury welcomed the news that the case against all officers was now officially closed.
Mr Rayney is pursuing a multimillion-dollar defamation action against police over the prime suspect claim.