The inquiry into Eastman's conviction for the 1989 murder of ACT police chief Colin Stanley Winchester has heard a covert recording of a phone conversation between a senior detective attached to Operation Peat, Detective Sergeant Thomas McQuillen, and forensic expert Robert Barnes, whose analysis of gunshot residue provided the link between Eastman and the murder scene.

They were chatting in January 1994, the year before Eastman's trial, about the findings of three overseas experts who had reviewed Mr Barnes' forensic work. Police had known early in their investigations they would need to have Mr Barnes' work reviewed, but Detective Sergeant McQuillen said the expert was highly resistant to the idea, fearing that it could cause the case to ''collapse''.

Two of the overseas reviewers returned reports stating they did not agree with Mr Barnes' conclusions.

The detective called Mr Barnes who, not knowing he was being recorded, expressed fears that the criticisms may make their way into evidence before a court.

''If we don't put a brake on these turkeys … I mean, we don't want these bastards putting that sort of stuff in writing,'' Mr Barnes said.

''They've got to be told, you don't say I do not agree. You ask questions, all right.'' At another point in the conversation, he talks about going overseas to talk to one of the experts who had reviewed his work. ''I'll beat him and I can talk him around,'' he said. ''The point is it's in writing and it can end up in evidence, knowing our friends in the DPP.''

Mr Barnes was called by the Crown in the case against Eastman in 1995, but was giving evidence as an independent expert. Despite that, Mr Barnes assures Detective Sergeant McQuillen in the conversation that he is a ''police witness''.

''And look, please don't be harassed because as we've discussed I'm going to work, you know, I'm working with you,'' he said.

''As far as I'm concerned I'm a Crown witness, a police witness.''

Counsel assisting the inquiry Liesl Chapman quizzed the detective on whether that phone conversation had given him ''serious concerns'' about Mr Barnes' independence, and whether he told the prosecution of his concerns. The former AFP officer said he had no such concerns about independence.

At another point in their taped phone conversation, Mr Barnes talks about the move by prosecutors to have his work reviewed by other experts. ''Well, my bottom line is, and this comes back to the other question I asked you before, what is going on, you know, from the Crown?'' Mr Barnes asked. ''It seems to me, quite frankly, there's only you and me that are really fair dinkum about this case.

''I get a strong impression by the fact that things have been given to people like [AFP forensic expert] James Robinson to check, that people don't either trust me, and I guess therefore follows that I'm in some sort of bloody cahoots to try and set up Eastman.''

Mr Barnes, a Victorian forensic expert, was charged with disciplinary offences following an internal investigation into his work by Victoria Police in 1992 and 1993.

The charges were not pursued after he quit the Victorian State Forensic Science Laboratory in 1993, still two years before Eastman's trial.

One of the key aims of the present inquiry is to determine whether the duty to disclose to the defence concerns about the reliability and veracity of Mr Barnes was complied with. Both Detective Sergeant McQuillen and the operation's leader, Commander Richard Ninness, knew about the internal investigation into Mr Barnes.

But the inquiry heard that no mention of the internal investigation had ever been found in AFP documents. Detective Sergeant McQuillen, whose role it was to liaise with Mr Barnes, said he did not know why that would be.

The detective never thought it necessary to further look at why the forensic expert was the subject of an internal investigation, but he said Commander Ninness had gone to Victoria over the issue.

He said he had been told the investigation into Mr Barnes related only to administrative issues, and would not affect his work on the Winchester case. He also said he did not consider a need for the prosecution to be informed of the investigation of Mr Barnes.

It also emerged that Detective Sergeant McQuillen had been warned that Mr Barnes was ''emotionally involved'' in the case, and had made concerning assertions about gunshot propellant.