David Eastman, the man jailed for almost 20 years for killing one of Australia's top police officers, has been awarded more than $7 million in compensation after he was found not guilty of the crime.

Key points: David Eastman is awarded $7.02 million after spending nearly two decades in jail for a murder he was found not to have committed

David Eastman is awarded $7.02 million after spending nearly two decades in jail for a murder he was found not to have committed The ACT Government had offered Mr Eastman an "act of grace" payment of more than $3 million, but he refused because it required that he waive his right to further compensation

The ACT Government had offered Mr Eastman an "act of grace" payment of more than $3 million, but he refused because it required that he waive his right to further compensation The 74-year-old previously told court of the despair and fear he felt in jail, and the assaults he had suffered

Mr Eastman was last year acquitted of the murder of Australian Federal Police assistant commissioner Colin Winchester in a retrial, clearing the way for a compensation bid.

Earlier this month the ACT Supreme Court heard Mr Eastman rejected an ex gratia payment from the ACT Government of more than $3 million, instead asking for at least $18 million in compensation.

The case has already cost the territory more than $30 million.

On Monday Justice Michael Elkaim added to that by granting Mr Eastman $7.02 million in compensation under the Human Rights Act and ordered the ACT Government to pay costs.

In a statement ACT Chief Minister Andrew Barr said the Government would consider the judgment and "respond promptly".

In explaining how he reached the compensation sum, Justice Elkaim referenced the hardships Mr Eastman faced in prison, including abuse by fellow inmates.

"It is also necessary to take into account the plaintiff's loss of his working life and economic capacity, the insult to his reputation, and also … the need to compensate him for the wrongfulness of his imprisonment," he said.

During the hearing Mr Eastman addressed the court and gave a written statement detailing his experiences in prison.

He said he had lost the opportunity to have a family and a career. He also said his two younger sisters and his mother had died while he was in jail, and the first thing he did when released was visit their graves in Sydney.

David Eastman 'relieved', eager to get on with life

David Eastman was arrested in 1992 and convicted three years later for killing Colin Winchester. ( ABC News )

Outside court, Mr Eastman's lawyer Sam Tierney said his client was "relieved" and "very happy" with the decision.

"He would like to thank the court for considering his matter so promptly," Mr Tierney said.

"He would also like to thank his lawyers and those members of the community who have supported him.

"Mr Eastman also expresses his wishes … that he would like to now get on with the rest of his life, if possible."

Mr Tierney said Mr Eastman considered the decision a "good outcome" but would take time to determine whether he would appeal the amount awarded.

"There is a right of appeal in the ACT — whether or not this is the end of the matter, we'll have to wait for that appeal period to expire to see," he said.

It is still unclear what Mr Eastman intends to do with the money.

"He's lost a significant chunk of his life and he's obviously got some thoughts in mind as to what he might do with it," Mr Tierney said.

Long legal battles before freedom

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

During Mr Eastman's years in jail he fought a long battle in the courts, including the High Court, for his release.

The breakthrough came in 2014 when an ACT Supreme Court board of inquiry was set up, run by Acting Justice Brian Martin.

The inquiry was sparked by claims of new evidence from an old friend of Mr Eastman, who said he could explain how gunshot residue got into Mr Eastman's car.

Benjamin Smith said he had taken Mr Eastman's car rabbit shooting before the killing, without Mr Eastman's knowledge. He also said that, on the day of the killing, Mr Eastman had been engaged in a long conversation with his mother.

The green, flattened, ball particles found in the car were critical to Mr Eastman's conviction at his 1995 trial, and used as evidence linking him to the crime scene.

Ultimately, Justice Martin dismissed the evidence, accusing Mr Smith of putting on a show in the witness box and describing his evidence as "utterly devoid of any credibility".

But it did the job, opening an inquiry that uncovered deep flaws in the evidence used to convict Mr Eastman.

'Unacceptable' forensic evidence

The man who became central to the inquiry was forensic scientist Robert Collins Barnes.

When he was called to give evidence, counsel assisting Liesl Chapman went from one gunshot residue particle to the next in a painstaking examination.

Others had questioned the evidence over the years, but the inquiry established there was no way to positively link the two scenes, and the residue in Mr Eastman's car was only circumstantial evidence.

Justice Martin was scathing in his final report, saying Mr Barnes's report had lacked a scientific basis.

"The provenance of crucial exhibits is either non-existent or highly doubtful … Fundamental data was not produced prior to trial," he said.

"In some instances it is apparent that Mr Barnes could not have undertaken the organic analyses upon which he claimed to have based his opinions.

"In other respects, the contemporaneous accounts strongly suggest that such analyses were not carried out and Mr Barnes's report was wrong."

The judge said Mr Barnes's explanations had ranged from unsatisfactory to unacceptable.

In a personal letter to the court during his compensation hearing, Mr Eastman said he was astonished by what emerged during the inquiry.

"I couldn't believe I had been convicted in the circumstances which were being revealed during the inquiry. I felt devastated and empty by what came out," he said.

Justice Martin found there had been a miscarriage of justice and recommended Mr Eastman's conviction be quashed.

He also said he was fairly certain Mr Eastman had committed the crime, but he still had a nagging doubt.

But his recommendation that there be no second trial, because of the passage of time, was ignored — the court ordered that another trial go ahead.

A second, and last, trial

Mr Eastman fought a retrial all the way, including through a failed stay application in 2016.

Then there were delays in starting the trial, after Mr Eastman objected to New South Wales Justice Anthony Whealy running the case.

The trial eventually began in June last year and ran for six months, overseen by Victorian judge Murray Kellam.

Mr Eastman faced a retrial last year, with a jury finding him not guilty of the murder. ( ABC News: Jordan Hayne )

Prosecutors maintained throughout that they still had a strong circumstantial case — and there was some valid forensic evidence.

New technology was used to prove which gun had been used in the killing.

It was a well-organised prosecution case by Sydney barrister Murugan Thangaraj, who told the jury there were too many coincidences for anyone else to have killed Colin Winchester.

But Mr Eastman's lawyer George Georgiou prevailed in the end.

He had run strongly on the alternative theory — that it was more likely an organised crime hit — and he had gently undermined the key elements of the Crown case throughout.

Perhaps the only witness who could have solved the case either way — the man who sold the gun days before the murder — had died without identifying Mr Eastman.

When the verdict of not guilty was returned, Mr Eastman mouthed "thank you" to the jury.

Colin Winchester's wife Gwen never saw the result. She died in February 2015, after spending years watching Mr Eastman fight the case from jail.

So who killed Colin Winchester?

For years rumours swirled that the execution-style shooting was an organised crime hit.

Colin Winchester had been involved in Operation Seville involving drug crops near Canberra.

He was acting under a ruse that he was protecting the crops, when he was really laying a trap for more senior distributors.

The circumstances provided a strong motive.

Secret evidence, including some new evidence about the involvement of organised crime, was presented to the Martin inquiry and in the trial in 2018.

Justice Martin remains the only person to have seen and been able to publicly canvass a view about the evidence. In his report, he said the material suggests a motive.

"Suspicion is generated but it does not rise to the level of a possible hypothesis," he said.

But he said fresh evidence that he heard in secret added a new dimension.

"It's now impossible to predict how that evidence would be received by a jury today, or what weight would have been given to it in 1995. But it cannot be ignored," he said.

"The fresh evidence potentially lifts suspicion to the level of a reasonable hypothesis consistent with [Mr Eastman's] innocence."

Nonetheless, Justice Martin noted the evidence was hearsay and the primary witness was "decidedly suspect".

The jury is unable to tell anyone what they thought about it, and whether it played a role in their decision, or whether they just thought the crucial link between Mr Eastman and the crime had not been established.

The only certain thing is that, to date, Colin Winchester's family still has no answers.