Ben Smith, a former relief teacher, has claimed he borrowed Eastman's car in 1985 or 1986 to go shooting in a dry creek bed just off the Monaro Highway, near Michelago.

He said he was coming back to the car when he noticed someone watching him, so he panicked and quickly put the gun back in the boot, without placing it in its case.

That story was used to cast doubt on the linking of gunshot residue found in Eastman's boot with the murder scene, which was a key part of the Crown's original case at the 1995 trial.

It was the first time that the former relief teacher and flatmate of Eastman's had given this new, potentially explosive evidence to any court.

But in his past two days of evidence Mr Smith was continually pressed over why he had never spoken of the hunting trip before and whether he had invented the story to help Eastman.

Mr Smith did not mention the hunting trip to police during two interviews in 1991, despite the topic of Eastman's car being raised.

Mr Smith did not tell a magistrate of the trip when he gave evidence at an inquest on Assistant Federal Police Commissioner Colin Winchester in 1992, despite being directly asked about whether Eastman lent his car out to others.

He first came forward with the story after Eastman - whom he has previously described as a ''good friend'' and someone he thought to be innocent - was convicted of the murder in 1995.

Counsel assisting the inquiry, Liesl Chapman, SC, accused Mr Smith of making up the story to help Eastman.

''Making it up? What are you suggesting?'' Mr Smith said.

''That you are making it up,'' Ms Chapman said.

''Well, I suggest you are talking rubbish because I didn't make it up,'' Mr Smith said.

Counsel for the office of the Director of Public Prosecutions, Peggy Dwyer, questioned Mr Smith about whether the hunting trip was nothing more than a ''false memory'', which he denied.

''I did, I did take [Eastman's car] for a spin,'' he said.

Counsel for the Australian Federal Police, Lionel Robberds, QC, accused Mr Smith of putting on a performance for the public and the media as a show of support for Eastman.

Mr Robberds pointed out aspects of Mr Smith's behaviour in the courtroom on Monday and Tuesday, during which he variously made remarks of ''committing sins'' with his wife, asked for a definition of ''truth'' while swearing an oath, asked Ms Chapman for her first name and asked questions of people in the public gallery.

Mr Smith had also asked acting Justice Brian Martin whether Eastman was watching the proceedings and repeatedly requested to speak with Eastman's defence team, saying he was hoping to be ''coached'' on what questions to expect.

The inquiry heard Mr Smith had also spoken with Eastman before his 1995 trial, when Eastman said ''the gunshot residue is going to nail me''.

Mr Robberds asked Mr Smith why he had not told Eastman about the hunting trip at that moment.

''Good point, good point. I was of the opinion that David was someone who would shoot himself in the foot,'' Mr Smith said.

''I left it a long time and I shouldn't have done.''

Earlier on Tuesday, Mr Smith claimed he had not realised gunshot residue evidence was being used against Eastman, so he had not thought the hunting trip in the borrowed car was important.

That is despite a string of articles in the late 1980s and 1990s, including in The Canberra Times, publicising the fact that gunshot residue had been found in a suspect's car boot.

It is also despite a note of a conversation between Mr Smith and former Director of Public Prosecutions solicitor Jennifer Woodward in 1994, in which Mr Smith is recorded as saying he was sure police had tampered with evidence in Eastman's car.

The inquiry continues on Wednesday.