The case of Troy Anthony Davis has been a rallying point for death penalty opponents and groups such as Amnesty International and the NAACP. Davis has insisted he was wrongly convicted of killing an off-duty Savannah police officer in 1989 - and that he had evidence to prove it.
Davis' lawyers argued key witnesses at Davis' trial had recanted their testimony. New witnesses claimed they heard another man confess to being the killer.
It was enough to persuade the U.S. Supreme Court a year ago to order a hearing on Davis' innocence claim, an extraordinary step not taken in more than 50 years. But the federal judge who heard the case in June ruled Tuesday that Davis' case wasn't nearly as strong as his attorneys suggested.
"Ultimately, while Mr. Davis' new evidence casts some additional, minimal doubt on his conviction, it is largely smoke and mirrors," U.S. District Court Judge William T. Moore said in his ruling.
Davis' lawyers vowed to appeal the ruling, though the precise legal route they planned was unclear.
"We are disappointed with the court's ruling and we strongly disagree with the court's findings and conclusions," said Stephen Marsh, one of Davis' appellate attorneys. "We believe that Troy is innocent."
Davis' attorneys have at least two paths for appeal. They could appeal directly to the U.S. Supreme Court, or they could seek a review from the 11th Circuit Court of Appeals in Atlanta.
Davis, 41, has been on death row since a Savannah jury convicted him in 1991 for the slaying of Mark MacPhail, an off-duty police officer who was fatally shot while rushing to aid a homeless man being attacked outside a bus station.
The victim's mother, Anneliese MacPhail, said she was pleased by the ruling but nervous that it may not stick.
"I'm not holding my breath," said MacPhail, 76. "We've been through to much to think this is over soon. For 19 years we've been going back and forth, and too often in the 11th hour something happens."
Davis has been spared from execution three times since 2007 as his attorneys pushed their argument that new evidence shows police ignored MacPhail's real killer as they rushed to pin the shooting on Davis.
A divided U.S. Supreme Court ordered the evidentiary hearing for Davis in August 2009. The move was extraordinary because federal death penalty appeals normally look only at questions of due process and violations of constitutional rights. Appeals based on condemned inmates' claims of innocence are routinely rejected.
In June, Moore heard two days of testimony from witnesses seeking to cast doubt on Davis' conviction. Two said they falsely incriminated Davis at his 1991 trial, either out of spite or under pressure from police. Two others said another man had confessed to being MacPhail's killer in the years since Davis' trial.
Davis' lawyers presented affidavits by several other witnesses, but didn't have them testify in Moore's court.
The judge concluded that several recanting witnesses had already backed off their incriminating statements during Davis' 1991 trial. Others, he ruled, simply couldn't be believed.
"To hear Mr. Davis tell it, this case involves credible, consistent recantations by seven of nine state witnesses," Moore's ruling said. "However, this vastly overstates his evidence."
The judge also discounted witnesses' stories that a man who was with Davis the night of the shooting, Sylvester Coles, later told them that he, not Davis, had shot MacPhail.
Davis' attorneys never called Coles to testify at the June hearing. The judge said Coles might have told people he killed MacPhail, even falsely to enhance "his reputation as a dangerous individual." Without putting Coles on the witness stand, the judge said, his accusers' statements had to be treated as hearsay.
Amnesty International said in a statment the high bar the court set for Davis to prove his innocence was "virtually insurmountable" and that Davis' hearing showed there's still doubt about his guilt.
"It would be utterly unconscionable to proceed with this execution, plain and simple," said Larry Cox, executive director Amnesty International USA.
Others who have advocated reopening Davis' case include former President Jimmy Carter, Pope Benedict XVI and Nobel Peace Prize laureate Archbishop Desmond Tutu.
Davis' sister, Martina Correia, said Tuesday her family wasn't giving up hope.
"We will continue to fight," Correia said.
AP writer Greg Bluestein contributed to this report.