Former public servant David Eastman left court this week "relieved" and "very happy" after a judge awarded him more than $7 million in compensation.

The 74-year-old Canberran spent most of his mid-life in prison for murdering the ACT's top police officer, Colin Winchester — a crime of which he was eventually found not guilty.

When the ACT Government announced this week it would not appeal against Mr Eastman's payout, it closed a case that spanned three decades and churned through countless millions of dollars.

Indeed, the Eastman saga is older than the territory government itself, which did not exist when Mr Winchester, an assistant federal police commissioner, was shot dead in 1989.

But the payment has not ended the arguments over why this case was stretched out for so long, how it was conducted and how much it ultimately cost taxpayers.

Counting the costs

ACT budget papers show that, before this month's compensation case, the Government had spent about $26 million on Mr Eastman over the past seven years.

That included funding an independent judicial inquiry into his flawed 1995 conviction and prosecutors' decision to go ahead with a retrial, against the inquiry's explicit advice.

But it excludes the costs of Mr Eastman's initial trial, two High Court challenges, his many other legal battles, his 19 years in jail — including in some of NSW's most violent prisons — and what was widely reported at the time as Australia's biggest-ever police investigation.

That investigation involved four police forces: Winchester's community policing colleagues, the federal police, and New South Wales and Victorian detectives, who explored the possibility that Calabrian mafia had ordered the police officer's assassination.

Federal Police assistant commissioner Colin Winchester was the head of ACT Policing. ( ABC News )

A lack of records, and the number of jurisdictions involved, makes estimating the financial costs of all these related matters impossible.

However, it hardly stretches credulity to suggest that pursuing, prosecuting, imprisoning and defending Mr Eastman (via legal aid) over three decades cost twice or three times the expenses of the latest inquiry and retrial — taking the amount beyond $60 million or even $100 million.

The retrial controversy

Brian Martin, the judge who oversaw the 2014 inquiry that set aside David Eastman's initial conviction, warned that a retrial would be neither feasible nor fair. But then director of public prosecutions Jon White went ahead anyway.

His decision split Canberra's legal fraternity and remains controversial. Bar Association president Steve Whybrow said many were still critical of the DPP.

"It was very hard to reconcile the public interest in a second trial for somebody who had done nearly 20 years in custody where there was such strong recommendations by the reviewing judge about the degree of impropriety in that trial," he said.

But Gary Humphries, who was the ACT's attorney-general at the time of the first trial, believed it was the only appropriate response.

"We're dealing with the assassination of the most senior public official in Australia that's occurred, and we couldn't leave that question unanswered," he said.

"The only way of dealing with that question at the time that the court overturned the original conviction was to proceed to a second trial, there simply wasn't any other way of dealing with it."

But Mr Humphries agreed with the government's decision to abandon any future appeals.

"The law is quite clear, a person in that position is entitled to compensation," he said.

"$7 million is probably an appropriately couched amount for somebody who spent nearly 20 years in jail for what is officially a crime they did not commit."

White has now retired. It was left to his successor, Shane Drumgold, to defend the DPP's position in the agency's latest annual report.

Mr Drumgold alluded to the criticism of his office only indirectly, saying:

"As one would expect with such a high-profile case, there was a great deal of media commentary and public interest following the jury verdict. Such public commentary is a very important part of the criminal justice system, as public confidence in the criminal justice system deserves close scrutiny."

Looming compensation dispute

The ACT Government will not challenge the Eastman payout in the courts, but it left the door open to changing the Human Rights Act, under which Mr Eastman was awarded compensation.

David Eastman's decades-long legal battle has finally been brought to an end. ( ABC News: Ian Cutmore )

In his compensation decision, Justice Michael Elkaim took aim at the Government's case.

"If the [Government's] argument was accepted, the scope of section 23 [under which compensation was granted] would be confined to only those few cases where there was subsequent new evidence — for example, the DNA of another person, a confession by another person or the establishment of an alibi — which showed the crime had been committed by someone other than the convicted person.

"It would not apply to cases where subsequent discoveries established a trial had been improperly conducted leading to a miscarriage of justice."

Justice Elkaim said he approached the amount of compensation from the basis that Mr Eastman was an entirely innocent person who had suffered through almost 19 years' imprisonment as a consequence of a miscarriage of justice.

In the wake of the decision, some, like Mr Humphries, believe there is scope for the government to change the law.

"I think that the act as it's been used here or applied here is a little bit blunt and inflexible and perhaps that should be moderated in the future," he said.

"I think it should be tempered with a provision that allows the executive or possibly some other decision-making body — the Civil and Administrative Tribunal, for example, of the ACT — to review a decision and decide whether it might be appropriate to have exemptions in certain extreme circumstances."

But Mr Whybrow disagreed, warning the Government to think carefully if it was planning to remove the right.

"It would be an unfortunate knee-jerk reaction … if the Government was to take away this right to compensation based on one really extraordinary case, which is not the usual case that this law will apply to," he said.

His use of language does not go unnoticed.

There has been nothing "knee-jerk" or remotely speedy about this 30-year-long legal saga — and nothing at all insignificant about the tens of millions of dollars (at least) it has cost ACT taxpayers.