Jon White, the DPP, went before the board of inquiry last year arguing that most of the terms of reference for the inquiry ordered by ACT Supreme Court Justice Shayne Marshall should be thrown out, because the judge had failed to apply the criteria imposed by the Crimes Act. Under this, a convicted criminal could get an inquiry only if there was fresh evidence, which could not have been available at the trial, raising doubts about the safety of the conviction, or if there was some fresh point, not considered or able to be considered before, raised. Nearly everything being put in favour of David Eastman's right to an inquiry had been considered and ruled on either at the trial, numerous appeals, or during two inquiries, White argued.

The inquiry told White firmly that these were points he should have raised before Marshall, not it. The inquiry derived its jurisdiction from Marshall's order: it was not, in effect, a court of appeal against Marshall, or in a position to second guess or read down his decision.

Since then, counsel for the DPP has continued, at the many directions hearings, to reagitate the issue, if in different ways. Two weeks ago, a formal submission went before the board, seeking once again to king-hit the inquiry, if on a slightly refined argument prepared by a recently engaged top Sydney silk.

The submission argues that the DPP, as an interested party, is entitled to particulars of what is alleged in the terms of reference of the inquiry, so that it can prepare its arguments and any evidence that it thinks will help the tribunal. It argues that it must be assumed that Marshall was following the rules of setting up inquiries - particularly as to the need for fresh evidence or arguments. Thus, it says, those particulars had to be interpreted as if Eastman should not be allowed to raise questions that had been dealt with before. The submissions - for which other counsel now have to be diverted from the case proper to reply - finish at the same end point as with White last year: an apparently open-ended inquiry would be so constrained there would be hardly anything to inquire into.

Eastman was convicted 18 years ago) of the murder of assistant AFP commissioner Colin Winchester 24 years ago. There was a strong chain of circumstantial evidence, despite his consistent claims of innocence, and concerns about the conduct of the trial, and the calibre of some of the evidence. The conviction has been, in effect, in non-stop litigation since, if not without previous unsuccessful attempts by DPPs of the time to prevent agitation of the doubts coming before the courts.

Counsel for the police argues that some of the materials - particularly details of a police investigation into the possible involvement of Calabrian organised crime in the Winchester murder - should remain restricted, even though more than 20 years old. At the time of his death, Winchester had been supervising a police sting operation on a cannabis crop at Bungendore. Most participants thought Winchester had been on the take and were astonished to discover he was doing his job.

The inquiry has also gathered evidence about the scientific findings made by Bob Barnes, the ''expert'' relied on by the AFP, and about the circumstances of his dismissal from the Victoria Police forensic science centre just before the trial. At a recent directions hearing, some sensational information emerged, capable of discrediting the whole trial. But this is now covered with suppression orders, after counsel assisting, Liesl Chapman, SC, belatedly said that allowing any reportage of it could compromise the investigations. It may be held back for the right theatrical moment.

Could success in establishing all, some or even one of the arguments contained in the terms of reference necessarily mean Eastman must be released? The inquiry is wrestling with this as an as-yet-unresolved preliminary point. Strictly, the inquiry is into whether there are matters that raise questions about Eastman's guilt. In that sense, it may not be enough to show the trial was a farce, that evidence was wrongly admitted, that there was police or prosecutorial misconduct, or that other things happened that should have rendered the trial a nullity.

In theory, any or all of this could be established without the board of inquiry necessarily concluding that there was material casting doubt on Eastman's guilt. The argument goes that it is not an inquiry into his conviction, nor an appeal. It is a reverse onus-of-proof inquisition into whether a reasonable person would now think Eastman could be innocent.

This was, in fact, the approach adopted by Justice Jeffery Miles, when, as ACT chief justice, he conducted an earlier narrow inquiry into Eastman's fitness to plead and instruct counsel. Miles ruled that Eastman's conduct and shenanigans during the trial reached a point where trial judge Ken Carruthers should have considered whether Eastman was fit to plead. He thought it had.

In a normal trial, if a question arises about mental fitness, the matter must be determined by a mental health tribunal, not the trial judge. But Justice Carruthers did not seem to consider the issue, or did, but did not think it arose. The prosecution did not raise the issue - though, late in the trial they produced an array of psychiatric reports on Eastman that did raise questions about his condition. Some of Eastman's lawyers had wanted to raise it, but had been forbidden by Eastman to do so.

Had Miles' finding - that there should have been an investigation into Eastman's fitness to plead - been made in an ordinary appeal, the conviction would have been quashed and, at the least, a new trial ordered. But Miles, using the distinction between a question about conviction and guilt, went on to consider what would have happened if Eastman had gone before a mental health tribunal. He thought that tribunal would have found him fit to plead. Now Justice Brian Martin is considering submissions about the same point.

Martin gave a bracing review of the conduct of the West Australian police in the Lloyd Rayney murder trial last year. Rayney had been accused on circumstantial evidence of murdering his estranged wife, a lawyer in the WA DPP's office. Martin was scathing about the quality of the investigation. His decision was not welcome to WA authorities, who appealed against it. That failed, and they thought to appeal to the High Court before an independent outsider (brought in, like Martin, to avoid any appearance of incest) threw in the towel.

In the ACT, the mechanisms for reviewing contested convictions, or the competence and quality of police investigations, are rather more primitive. A substantial police task force on the Eastman review is rather more focused both on defending the old investigation and the verdict, and protecting its reputation and its pitch, than in participating, with fresh and open minds, in a search for the truth.

The observer can be excused for thinking the DPP is spending hundreds of thousands of dollars primarily to protect the reputation of his office. In most states of the union, that would not give even a right to appear. It's about Eastman, not the police or the DPP.

Jack Waterford is editor-at-large.

jack.waterford@fairfaxmedia.com.au