A key prosecution witness in the Corryn Rayney case claims she felt threatened and intimidated by police over five years because they believe she has been holding back information about the murder.
Lawyer Clare O'Brien said she fled Perth at the height of the police investigation into her former colleague Lloyd Rayney and has stayed out of WA, fearing that police would implicate her in the murder.
Ms O'Brien was praised as an honest witness by Justice Brian Martin at Mr Rayney's recent trial, in which he was acquitted of killing his wife.
Ms O'Brien spoke for the first time about why she gave the defence team information before the hearings and decided to reveal during cross-examination that police took her statement under duress.
She claimed that in December, detectives from Operation Dargan flew to Sydney to interview her and attempted to coerce her into giving a statement "that fit with their theory about Lloyd", using the threat of malicious allegations that could have caused her public embarrassment at the trial.
Ms O'Brien told _The Weekend West _she complained to prosecutors but believed she was being ignored, so she "had no choice" but to engage her own lawyer, friend and barrister Belinda Lonsdale, shortly before she was due to testify.
She said she was made to feel "like a criminal, not a prosecution witness" and met Mr Rayney's lawyers with Ms Lonsdale.
"The defence told me their intention wasn't to hurt me or to affect my reputation or career whereas the police have been threatening to ruin my reputation, my career and my relationship," she said.
"The detectives kept on saying, 'Tell us more, we know you're withholding something', but I had told them everything I knew. They still don't believe me.
"I gave them four or five interviews, all for more than three hours, without a lawyer, to show them I had nothing to hide. It felt like they wanted me to say anything to bury Lloyd."
Ms O'Brien, who was a crown prosecutor for 10 years before moving to Legal Aid, said she became terrified during the police investigation in 2007 that she would "end up in Bandyup" women's prison because of a police theory that a man who had been tried and acquitted of a 2004 bikie murder, Johnny Montani, was involved in the murder.
"They were convinced that there was a third person involved and that was a hit man and it just so happened that Lloyd had represented an alleged hit man and that was Johnny Montani," she said.
"They implicated me in their theory because I recommended Lloyd to the Montani family because they were looking for a barrister without links to bikie gangs. "I have never met Johnny Montani or his family but the detectives just ran with it. I left Perth when that whole Montani theory was going. The police had me under surveillance."
Ms O'Brien said some of the Operation Dargan officers were good to deal with but others should be investigated by the Corruption and Crime Commission. She believed the detectives' conduct, and her claim that her complaint to the prosecution was apparently ignored, should be investigated.
Chief prosecutor John Agius, who is believed to be working on a submission to appeal against Justice Martin's decision, declined to comment.
Police Commissioner Karl O'Callaghan has said no public comment on the case would be made by police during the appeal period, which expires this month. It said WA Police were considering Justice Martin's decision.
Mrs Rayney's sister, Sharon Coutinho, backed the Operation Dargan detectives.
"They are very committed to solving my sister's murder and I believe they have done their best under very difficult circumstances," she said.
Ms O'Brien said she had not spoken to Mr Rayney since 2007 and believed he was innocent.
In his judgment, Justice Martin described the behaviour of detectives towards Ms O'Brien in 2007 as "the type of police conduct that should not be tolerated".
"Those officers misused their position of authority and threatened to abuse their power of arrest which should only be exercised when the evidence justifies an arrest," he said. He also referred to police behaviour in the case as "reprehensible".