Robert Barnes' evidence proved damning of Eastman over the 1989 murder of Federal Police Assistant Commissioner Colin Stanley Winchester, linking him with what the expert said was PMC brand ammunition particles, found in the accused's car and at the scene of the murder.

But the present Eastman inquiry is slowly picking over Mr Barnes' work, raising a series of questions about its veracity and reliability.

Mr Barnes gave evidence at trial and the inquest on Mr Winchester's death about a ''significant characteristic'' of PMC ammo, something he described as its tendency to keep its round shape after firing. He used that characteristic to exclude other ammunition, including Winchester brand, from the particles found in the car and at the scene.

At Eastman's trial, a photo of the particles was handed to the jury which Mr Barnes used to show the ammunition's tendency to keep its shape after firing.

But Mr Barnes' colleague at his Victorian forensic lab, Norbert Strobel, had produced a similar photo of PMC particles as part of a thesis he was working on.

The two photos were shown side by side to Mr Barnes at the Eastman inquiry on Wednesday, before the expert was questioned by inquiry head Acting Justice Brian Martin.

''Seriously, Mr Barnes, the one at trial does not show any particle that has lost its shape, does it?'' he asked.

''It's vastly different, isn't it, from the particles in [Strobel's] thesis?''

The judge then asked whether the jury would recognise the difference between the two photos.

''When I look at the photo on the left, it looks pristine,'' Acting Justice Martin said.

''Did you select that deliberately because it supported your argument?'' Mr Barnes denied that he selected the pictured to help ''bolster'' his evidence.

The expert did not prepare a single report in the six years between 1989 and 1995 setting out the tests, observations, and findings on which he based his assertion that PMC ammunition kept its shape. Counsel Assisting, Liesl Chapman, SC, questioned Mr Barnes over why no reports had been made to back up that crucial aspect of his evidence.

Mr Barnes said he only completed reports on request, and the AFP had never asked him.

''Is that your best answer to why, in six years, you didn't produce a report?'' Ms Chapman asked.

Mr Barnes: ''I produce reports as requested by the AFP. I wasn't asked for one, so I didn't prepare it.'' He said he discussed the issue with PMC ammunition with his colleague, Mr Strobel, and he had agreed that it kept its shape after firing.

Mr Strobel has already given evidence to the inquiry that he never discussed the issue with Mr Barnes.

The inquiry continues.