Atlanta (CNN) -- Georgia's parole board convened Monday morning to hear a last-minute appeal by Troy Davis, who is set to die by lethal injection for the murder 21 years ago of a Savannah police officer.
A jury convicted Davis of murder in 1991, paving the way for his execution, which has been delayed three times and is now scheduled for 7 p.m. Wednesday at a state prison in Jackson, Georgia.
The Georgia Board of Pardons and Paroles noted in a press release Sunday it is "the sole authority in Georgia for granting clemency to inmates." Options for the board include commuting a death sentence without parole, giving a convict a life sentence or denying clemency -- which, in this case, would pave the way for Davis' execution.
In addition to Davis and his supporters making their appeal, the victim's mother, Anneliese MacPhail, told CNN this weekend that she, too, plans to attend.
Many of Davis' supporters, who believe he was wrongly convicted and have staged rallies in recent days calling for his release, will not be allowed in. But in a statement Sunday, officials with Amnesty International, the NAACP and Georgians for Alternatives to the Death Penalty issued a fresh appeal for people to join them Monday for prayers, musical performances and speeches outside the building where the board will meet.
According to these groups, there have been about 300 rallies, vigils and events worldwide since last week. In addition, they say that more than 1 million people have signed a petition in support of Davis' bid to be exonerated.
Since his 1991 conviction, seven of the nine witnesses against him have recanted or contradicted their testimony. There also have been questions about the physical evidence -- and, according to some, the lack thereof -- linking Davis to the killing.
But the mother of Mark MacPhail, the police officer killed that night, said that those rallying don't understand all the facts of the case. She is convinced that Davis shot her son, and that the jury's decision to convict him was fair.
"I'm not out after blood, I'm after justice," said Anneliese MacPhail, adding she doesn't plan to attend the execution. "I want my son to rest in peace."
In a 2008 statement, then-Chatham County District Attorney Spencer Lawton described how Davis was at a pool party in Savannah when he shot another man, Michael Cooper, in the face. Davis was then driven to a nearby convenience store, where he pistol-whipped a homeless man, Larry Young, who'd just bought a beer.
Soon thereafter, prosecutors said MacPhail -- who was working in uniform, off-duty, at a nearby bus station and restaurant -- arrived. It was then, the jury determined, that Davis shot the officer three times, including once in the face as he stood over him.
Davis' lawyers, in a petition to a U.S. District Court, insisted that there is "no physical evidence linking" Davis to MacPhail's murder. They point, too, to "the unremarkable conclusion" of a ballistics expert who testified that he could not find definitively that the bullets that wounded Cooper and killed MacPhail were the same.
Georgia's attorney general, in an online statement, claims that the expert said the bullets came from the same gun type and noted that casings at the pool party shooting matched -- thus came from the same firearm as -- those found at MacPhail's murder scene.
Two decades ago, a jury convicted Davis on two counts of aggravated assault and one each of possessing a firearm during a crime, obstructing a law enforcement officer and murder. The latter charge led, soon thereafter, to his death sentence.
While reviewing Davis' claims of innocence last year, the U.S. District Court for the Southern District of Georgia found that Davis "vastly overstates the value of his evidence of innocence."
"Some of the evidence is not credible and would be disregarded by a reasonable juror," Judge William T. Moore wrote in a 172-page opinion. "Other evidence that Mr. Davis brought forward is too general to provide anything more than smoke and mirrors," the court found.
The Rev. Raphael Gamaliel Warnock, who is set to testify before the parole board Monday, said that he "can only begin to imagine the pain (the MacPhail family) must be feeling."
MacPhail "was protecting the community, and there is no pain greater than when a parent loses a child," Warnock said.
Still, he believes "there is too much doubt in this case for an execution."
"I have met with (Davis) on death row," Warnock said. "I believe he is innocent."
The odds do not appear to be in Davis' favor. The parole board denied him clemency once before. And the board has never changed its mind -- on any case -- in the past 33 years.