David Harold Eastman has been released from prison after his conviction for murdering a top police officer was quashed by the ACT Supreme Court.

Eastman was released on bail pending a retrial, after agreeing to strict conditions imposed by the ACT Director of Public Prosecutions (DPP).

Eastman has served more than 19 years in prison after being found guilty of killing Australian Federal Police assistant commissioner Colin Winchester in 1989.

In May an inquiry found Eastman had not received a fair trial, primarily because of flaws in the forensic case, and recommended his murder conviction be quashed.

On Friday he left Canberra's Alexander Maconochie Centre escorted by police, after the court ordered the conviction be quashed and that a retrial be held, at the DPP's discretion.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Listen Duration: 5 minutes 40 seconds 5 m Court quashes Eastman's 1980s murder conviction Download 10.4 MB

In its decision, the court said the circumstances and gravity of the offence, together with the life sentence imposed, were compelling factors that weighed heavily in favour of ordering a retrial.

"If we do not order a retrial, Mr Eastman's guilt or otherwise will never be determined.

"Whilst Mr Eastman would of course be entitled to the presumption of innocence, in our opinion it is not in the interests of justice for the controversy as to his alleged role in the murder to be left unresolved when there remains a strong circumstantial case against him."

Critical witnesses in the case may have died: lawyer

The bail application was not opposed by the DPP but strict conditions were attached.

The DPP sought conditions including that Eastman should go to an address outside the ACT and that he should inform authorities if he travelled from that address.

They also included not contacting more than 200 people, including members of the Winchester family.

After an adjournment, Eastman accepted these conditions with some small changes and was granted bail.

The conditions imposed will be reviewed in three weeks.

The ACT DPP said he was still considering whether to run a new trial.

Sorry, this video has expired David Eastman freed from Canberra jail after murder conviction quashed ( Elizabeth Byrne )

John Boersig from the Legal Aid Commission, which acted for Eastman during Friday's proceedings, read a statement outside the court after the decision was handed down.

"Throughout the long history of this case Mr Eastman has strenuously asserted his innocence," he said.

"He's relieved, finally, to be exonerated and to regain his freedom after 19 years."

Dr Boersig said Eastman wanted to thank his lawyers and all others who had supported him.

"He is looking forward to resuming an active and normal life including seeking employment and would greatly appreciate it if his privacy could be respected."

Dr Boersig said Eastman would not be making any further comment to the media until the question of a retrial was dealt with.

Terry O'Donnell, a former lawyer for Eastman, spoke to the media outside the court after the decision was handed down.

"We're back to where we were in December 1992," he said.

"There's still one more step to go but I believe Mr Eastman has a strong defence case, that's if the matter is ever to go to trial again.

"There is much that hasn't properly been canvassed yet."

Mr O'Donnell was Eastman's lawyer at the beginning of the trial in 1995, and the latest inquiry into Eastman's conviction was set up after he came forward with new evidence about how gun residue came to be in Eastman's car.

He said he believed there would be significant difficulties in a retrial.

"Critical witnesses that were never tested at the coronial inquest or the trial have died," he said.

Eastman to be treated like any other prisoner: Attorney General

Eastman huddles under blankets in the back of a car, after his release from Canberra's Alexander Maconochie Centre. ( 7.30's Chris Kimball )

ACT Attorney General Simon Corbell said his thoughts were with the Winchester family.

"[Friday's] developments will not be welcomed by them and my thoughts are with them at this time,” he said.

Mr Corbell said Eastman would be treated "like any other prisoner" on his release.

"The Government's policy is that no detainee is released into homelessness following their period of imprisonment,” he said.

"The Government will be utilising its through-care program to provide appropriate support and assistance to Mr Eastman."

Mr Corbell said the cost of the inquiry had been significant to the ACT Government.

"Certainly in the order of over $10 million has been spent to assist the conduct of the inquiry into Mr Eastman's conviction," he said.

Meantime, the ACT Victims of Crime Commissioner John Hinchey told 666 ABC Canberra the court's decision was distressing for Mr Winchester's family.

"This is another day of mourning for the Winchester family," he said.

"They are disappointed in the result. They don't wish to speak publically on the matter.

"However they do want to extend their gratitude the AFP and the DPP for their pursuit of justice for Colin Winchester."

Police officer shot in neighbour's driveway

In Friday's decision the court described the Eastman matter as "a wholly exceptional case" and found that despite the time that has elapsed since the offence, and the time that Mr Eastman has already spent in custody, it was an appropriate case to order a new trial.

The judges found that if a retrial went ahead, it would be open to Eastman to seek a permanent stay.

To be granted a permanent stay, Eastman would need to demonstrate that he could not be fairly tried, that a further trial would be seriously and unfairly burdensome, there was an abuse of process, or that a retrial would bring the administration of justice into disrepute.

Mr Winchester was shot as he got out of his car in his neighbour's driveway at Deakin on January 10, 1989.

Eastman became a suspect in the case, the day after the killing.

Detectives targeted Eastman who had threatened Mr Winchester after he refused to help him have an assault charge withdrawn.

Eastman believed if he was convicted for that crime it would thwart his bid to rejoin the public service.

He was eventually convicted of killing Mr Winchester in 1995 and sentenced to life in jail.

He has long protested his innocence, through numerous appeals including in the High Court.