The cold-blooded murder of Colin Stanley Winchester, the ACT region's police chief, is one of Australia's most notorious and hotly debated crimes.

An inquiry earlier this year recommended the conviction of disgruntled public servant David Harold Eastman - imprisoned for the crime almost 19 years ago - be quashed.

The ACT Supreme Court will now decide his fate this afternoon.

So how did we get to this point?

The Eastman Inquiry, which could end up costing the taxpayer roughly $4million, has spent this year and some of last looking at issues surrounding the prisoner's conviction.

The inquiry's extraordinary finding could see the convicted murderer freed after almost 19 years behind bars.

It took six months, thousands of pages of documents, dozens of ageing witnesses, and countless hours of public hearings, but the Eastman inquiry's report finally came up with a finding.

Here's a brief snapshot of what we learnt:

FORENSICS

When Eastman was sentenced, the judge said the case involved "one of the most skilled, sophisticated and determined forensic investigations in the history of criminal investigation in Australia".

That's almost laughable now. The work of expert Robert Collins Barnes, whose gunshot residue analysis provided a critical link between Eastman and the murder scene, has been almost completely debunked in the inquiry, losing nearly all credibility and reliability.

POLICE HARASSMENT

The inquiry has heard new evidence of the "in your face" tactics used by police against Eastman in the years following the murder.

Counsel Assisting, Liesl Chapman, SC, says it is now open to the inquiry to find police believed their tactics would cause Eastman to utter confessional statements in his bugged home, which he eventually did. If that was known, Ms Chapman says, there could have been an application to exclude the confessional evidence used against Eastman at trial.

OVERWHELMING CASE

Despite all the revelations of the Eastman inquiry, there remains a significant body of circumstantial evidence pointing towards Eastman's guilt.

The Australian Federal Police and Director of Public Prosecutions say the remaining evidence, minus the now debunked forensics, is "overwhelming" and proves a motive, threats, access to firearms, identification, and the fact Eastman, who even the AFP have described as one of the most intelligent humans on Earth, could not explain his whereabouts when asked by police the next morning.

The AFP and DPP say the case remains so strong that the inquiry head, Acting Justice Brian Martin, should decide Eastman was guilty of the murder and not interfere with the conviction, even if there has been a miscarriage of justice.

THE MAFIA LINK

Speculation that the Calabrian Mafia, or 'Ndrangheta, was responsible for the killing has simmered away since the year of Mr Winchester's death. The inquiry looked at evidence relating to this alternative hypothesis, although much of the material remains suppressed.

Eastman's counsel, Mark Griffin, QC, argued the evidence of organised crime involvement is strong and rational, and that, at the very least, it should be a counterweight against the remaining circumstantial case against his client.

THE RABBIT SHOOTING STORY

One of the highly anticipated fresh pieces of evidence to come before the inquiry was the story of Benjamin Smith, a former school teacher and friend of Eastman. He told the inquiry he borrowed Eastman's car to go rabbit shooting, which could have explained the gunshot residue found in his Mazda.

This story went nowhere, and the credibility of Mr Smith, a highly eccentric witness, was torn apart by repeated lines of cross-examination. The evidence was so flimsy that, when Mr Smith finished, Acting Justice Martin asked the gathered lawyers to make submissions on "why I should believe a word of what I've just heard in the witness box".

THE DOCTOR'S EVIDENCE

An important piece of evidence against Eastman at trial was that of his GP, Dr Dennis Roantree, who said his patient became angry after a conversation about Mr Winchester and said "I should shoot the bastard". Eastman wasn't legally represented at the time of Dr Roantree's evidence, and questions were never asked about "a niggling doubt" the doctor felt about his evidence, or whether the threat was a passing quip made after Eastman's anger had subsided. Evidence was also not taken from Dr Roantree's daughter, who was near the consultation room at the time and suggested Eastman's anger had dissipated by the time he left the room.

What the inquiry has heard may have been enough to change the complexion of the doctor's evidence about the threat. But Dr Roantree also told the inquiry of Eastman's "unbelievable fury" at the time, saying that was more important than any words he had uttered.

THE TRIAL JUDGE

Eastman's lawyers have tried to use the inquiry to argue that the 1995 trial judge, Ken Carruthers, was tainted by apprehended bias. A former deputy registrar of the court told the inquiry she had seen the judge in possession of mental health reports on Eastman, and the inquiry has investigated whether he got those reports in an appropriate manner.

Acting Justice Martin has already indicated he believes the trial judge got the reports in the proper way and does not think a finding of apprehended bias has been made out.

FITNESS

The inquiry also revisited issues to do with Eastman's mental health, and whether his fitness to stand trial was properly considered during the proceedings. Eastman's lawyers argued the murder trial should have been adjourned on or before June 29, and the accused referred to a tribunal to rule on whether he was fit.

The inquiry's counsel assisting has submitted she doesn't believe the evidence shows any issue or question about Eastman's fitness that goes above what was identified in the last inquiry, the 2005 Miles inquiry.

DISCLOSURE

A key question the inquiry tried to resolve is whether the prosecution, including the AFP, failed in its duty to disclose all the necessary information relating to the case, particularly about Barnes, to Eastman's defence team.

Some information, such as file notes from the DPP's conferences with overseas experts who had reviewed Barnes' work, was not disclosed, although not due to any intentional deception. There is also uncertainty surrounding the disclosure of some of Barnes' own reports. Police did not disclose Barnes was the subject of an internal investigation in Victoria, thinking it was only minor in nature, or of an interview between a senior Operation Peat detective and Barnes, in which the supposedly independent expert describes himself as a "police witness" and expresses reluctance to having his work reviewed by others.

WHERE TO NOW?

The delivery of Acting Justice Martin's report concluded the functions of the board of inquiry. The report is now with the ACT Supreme Court, and a full bench will decide to either; quash the conviction, quash the conviction and order a re-trial, or confirm the conviction. A pardon can also be granted by the ACT executive, but that appears unlikely. A re-trial so many years on is also deemed next to impossible.

It is unknown when the full bench of the Supreme Court will sit, but it can only have regard to Acting Justice Martin's report, and nothing else. Given the strength of his recommendations, the Supreme Court would be unlikely to differ from the path the inquiry has urged.