Accused killer David Eastman has lost his last-ditch bid in the country's highest court to stave off a planned retrial for the shooting death of police chief Colin Winchester.
Eastman, 71, failed in an attempt to block a second trial for the alleged murder of Mr Winchester, 55, who was Australian Federal Police assistant commissioner when he was gunned down in his Canberra driveway in January 1989.
An ACT Court of Appeal decision in December had already cleared the path for Eastman, a former public servant, to face a mammoth second trial after a protracted series of legal fights spanning more than two decades.
Eastman sought permission to challenge that ruling in the High Court, filing an application for special leave to appeal in early January.
But the court threw out that application on Thursday morning, refusing to hear an appeal, making it all but certain Eastman will face an ACT Supreme Court jury, for a second time, later this year.
Neither Eastman or his lawyers were in court for the decision.
Eastman's retrial is set to be heard over six months by Acting Justice Murray Kellam, QC, from July. More than 300 witnesses are expected to be called.
That conviction was eventually quashed in 2014 after a court found he did not get a fair trial and he was released from prison after serving more than 19 years of a life sentence.
But the court, while quashing his conviction due to fundamental errors in forensic analysis, also ordered he face a fresh trial for the alleged murder.
That prompted Eastman to launch an application for a permanent stay of proceedings.
His lawyers argued a retrial would not be fair and shouldn't go ahead due to weaknesses in the Crown case, failures of disclosure and unfair conduct by police and prosecution lawyers and extensive media coverage.
The delay since the alleged murder was also said to put him in an unfair position.
Eastman also argued his personal circumstances, including his age, mental health and time already served, weighed against a second trial going ahead.
Acting Justice David Ashley last year threw out that application, but kept his reasons secret so as not to jeopardise the fairness of the retrial.
Eastman challenged the court's decision in the ACT Court of Appeal.
His legal team argued parts of the judge's decision could give the appearance of bias during a hearing, much of which took place in closed court, in October.
Lawyers argued the judge erred in assessing the significance of the prosecution's failure to disclose relevant material, and failed to place sufficient weight on factors which meant the retrial would be unjustifiably oppressive to Mr Eastman.
They said he didn't place enough weight on factors which would likely compromise the fair presentation and consideration of Mr Eastman's defence at any retrial, or on points which meant a retrial would bring the administration of justice into disrepute.
The appeal was thrown out in December.
"In its decision refusing Mr Eastman leave to appeal, the Court of Appeal was not persuaded that Acting Justice David Ashley's decision was attended by apprehended bias, or that any of the other matters put forward by Mr Eastman should have led to a permanent stay being granted," the judges' decision stated.
The court did not publish the judges' reasons to protect the fairness of the retrial.
Their decision prompted Eastman, through his Legal Aid ACT lawyers, to affirm his innocence and vow he would continue to fight the allegations.
Thursday's rejected application was not Eastman's first failed High Court bid in his long-running legal saga.
He was granted special leave to appeal his murder conviction in the court in 1997, but that appeal was dismissed in 2000.
A second application was knocked back by the court in 2007.