A memo from a senior officer at the Victoria Forensic Science Centre (VFSC) to Detective Inspector Paul Sheridan, of Victoria Police, said the scientific witness, Bob Barnes, had gone into private practice as a forensic investigator, was charging hefty fees, was trying to establish himself as quickly as possible and his urge to impress by assisting to extremes was affecting how far he went with some points.

He was also misrepresenting his expertise, whether as a firearms expert or a ballistics expert, Inspector Sheridan was told.

Inspector Sheridan was being briefed for a possible attack on Mr Barnes's expertise in the Coulston murder trial in Victoria, but the comments were made in a paragraph relating to evidence he had just given in the Eastman trial, in a different jurisdiction.

In 1995, David Harold Eastman was convicted of the January 1989 shooting murder of Australian Federal Police Assistant Commissioner Colin Winchester at his home in Deakin.

Ashley Coulston was the Burwood triple murderer and suspected ''balaclava killer''. Mr Barnes had been engaged by Coulston's defence team to attack evidence presented by another expert but, according to the VFSC, his statements were factually incorrect on some critical matters, and he misrepresented and exaggerated his abilities.

Mr Barnes had been dismissed for scientific misconduct by the VFSC in 1993 after serious concerns were raised about evidence he had given in a number of cases, and after an internal review of his cases had shown a persistent failure to follow established procedures for examining and recording evidence.

But this was not generally known at the time. The AFP used Mr Barnes as one of its forensic experts after Mr Winchester was shot dead in the driveway of his home. Mr Barnes's findings were critical in linking gunshot residue in bullet cartridges found near the murder scene with cartridges fired through a particular gun and, later, with microscopic gunshot residue said to have been found in the boot of Eastman's car.

But the jury, judge and defence team were not told by the Director of Public Prosecutions, or police, about Mr Barnes's dismissal or the doubts that had arisen about his methods. Mr Barnes's evidence at the trial, which varied in significant respects from evidence he had given at the inquest into Mr Winchester's death, was not cross-examined by the defence, and its weaknesses, or discrepancies, were not explored. Eastman suffered mental illness and repeatedly dismissed counsel in the trial. Mostly, when unrepresented, he refused to participate. The trial judge, who believed that Eastman was faking in an effort to achieve a mistrial, allowed the case to proceed.

It is only now, 17 years after the conviction, and nearly 24 years after the services of Mr Barnes were first engaged by the Winchester investigation, that Victoria Police has released its files on Mr Barnes, after a freedom of information request by The Canberra Times last year. Mr Barnes initially appealed the decision to grant access but ultimately withdrew his appeal.

The files show increasing judicial concerns about the evidence given by Mr Barnes in various Victorian cases and inquests, including accusations of misleading courts, lying and being evasive, defensive and defiant in cross-examination. In one case he was accused of ''setting out to prove [an accused woman] had fired the shots, and lied and misled to achieve that aim and protect himself from criticism for having done so''. He was also accused of doctoring a photograph to omit, from material tendered in court, particular identification marks that would not have assisted the prosecution case. Initial VFSC inquiries might themselves have been described as defensive.

They recognised that some of his procedures and records were deficient, but seem to regard them as mere technical breaches, raising no fundamental difficulties with his findings.

As one VFSC briefing note put it, ''the facts remain that the courts have had several opportunities to challenge Barnes's acceptance as an expert witness and also ample opportunities to challenge his evidence and or his opinions''.

Both police and VFSC managers initially tended to think criticism of Mr Barnes was nitpicking. They did not think that dishonesty or technical incompetence had been demonstrated.

Increasingly, however, the tone of reports becomes more critical, extending to the realisation that Mr Barnes had removed hundreds of files from the centre, that he had issued reports that had not been peer reviewed, and was given to using phrases - such as saying that two samples were ''indistinguishable'' - that were apt to seriously mislead others.

In June 1996, a senior VFSC manager flew to Sydney to discuss, for four hours, six cases in which Mr Barnes had given evidence in NSW investigations, the VFSC reviews and corrective actions taken. There was no record of a similar briefing for the AFP but a briefing note expressly disclaimed any responsibility for any advice Mr Barnes had given in relation to the Winchester case.

''With regard to other interstate and overseas cases, those that Barnes undertook while an employee of Victoria Police appear not to be a problem with the possible exception of the Winchester matter from the ACT,'' a 1996 briefing note to the Victoria Police assistant commissioner (crime) says.

''In this matter Barnes performed a considerable amount of work while at VFSC but completed most of that work, and performed additional work, while at the Australian Government Analytical Laboratories, the reports of which were not subject to VFSC quality management.

''Barnes's VFSC reports re Winchester were not checked through normal VFSC systems [bypassed by Barnes] and it is believed that at least one was dictated by Barnes directly to AFP police as they could not extract them from Barnes by telephone and written requests.''

The report writer appeared to think that the Eastman team knew all about Mr Barnes's VFSC career. It predicted Mr Barnes's credibility would come under heavy attack at the appeal.

''The implications for VFSC and Victoria Police are restricted to the issue that he failed to follow all procedures on all occasions, and in doing so placed himself outside of the very rules that provide the framework in which VFSC staff are to operate and the protection that that provides,'' the memo said.

''It remains that the court must test the evidence, and the expert witness stands or falls on his/her performance on the day, as is always the case.

''If at the Winchester appeal Barnes's gunshot residue evidence is not allowed, this is not to say it is wrong per se, but may be considered by the court to be 'unsafe' in the overall context of their deliberations, a commonly encountered situation with DNA evidence.''