JACKSON, Georgia (CNN) -

The fate of condemned Georgia convict Troy Davis was in the hands of the U.S. Supreme Court late Wednesday as hundreds waited past nightfall outside the prison where he was to be put to death.

Davis had been scheduled to die by lethal injection at 7 p.m. ET for the 1989 killing of Mark MacPhail, an off-duty Savannah police officer. But the proceeding was delayed as the justices pondered a plea filed by his attorneys less than an hour earlier, after last-ditch appeals failed throughout the day.

Several hundred people, most of them opposing the proceeding, gathered outside the state prison in Jackson where Davis awaited his fate. Others held a vigil in a nearby church. Police in riot gear and body armor stood guard over the gathering, and at least three people who crossed the street were taken away in handcuffs.

His supporters argued that his conviction was based on the testimony of numerous witnesses who had recanted, including a jailhouse informer who claimed Davis had confessed.

"There's a genuine feeling among people here and across the nation that we're about to do the unthinkable," said Isaac Newton Farris Jr., president of the Southern Christian Leadership Conference.

But prosecutors have stood by the conviction, and every appeal -- including the last-minute petitions filed Wednesday -- has failed.

Davis's supporters cheered and hugged each other when news of the delay reached them. But it did not sit well with McPhail's mother, who remained at home.

"This delay again is very upsetting and I think really unfair to us, because we want this situation closed," the slain officer's mother, Anneliese MacPhail, told CNN's "Anderson Cooper 360." She said the execution would bring her "relief and maybe some peace."

Davis' attorneys started the day by asking a judge in Jackson, where Georgia's death row is located, to halt the proceeding, citing a new analysis they say shows ballistics testimony at his trial was "inaccurate and misleading." They also note that a federal judge found in 2010 that a jailhouse informer's testimony that Davis confessed to killing Officer Mark MacPhail was "patently false" and that prosecutors knew a key eyewitness account was wrong.

"Clearly, the fact that Mr. Davis's death sentence rests in part on 'patently false' and egregiously inaccurate and misleading testimony, evidence and argument renders the death sentence fundamentally unfair, unreliable and therefore violative of the Eighth and Fourteenth Amendments," his attorneys argued in a motion filed Wednesday morning.

That appeal was denied Wednesday afternoon. The state Supreme Court followed suit a short time later, leading his attorneys to turn to the U.S. Supreme Court in the final hour before the execution.

Davis has been scheduled to die three times before, most recently in October 2008. That time, the U.S. Supreme Court halted the execution two hours before it was scheduled to take place.

This time, Davis declined to request the special last meal offered inmates prior to execution and was offered a standard meal tray: Grilled cheeseburgers, oven-browned potatoes, baked beans, coleslaw, cookies and a grape drink.

His case has drawn international attention, with Pope Benedict XVI, South African anti-apartheid leader Desmond Tutu and former President Jimmy Carter saying the execution should be called off. Amnesty International and the NAACP have led efforts to exonerate Davis, and U.N. human rights officials joined those calls Wednesday.

"Not only do we urgently appeal to the government of the United States and the state of Georgia to find a way to stop the scheduled execution, but we believe that serious consideration should be given to commuting the sentence," read a joint statement from the U.N. special rapporteurs on arbitrary executions, judicial independence and torture.

But the man who originally prosecuted the case, Spencer Lawton, said those who do not believe there is physical evidence in the case are wrong.

"There are two Troy Davis cases," Lawton said Tuesday. "There is the legal case and the public relations case. We have consistently won in court, and consistently lost in the public relations battle."

Since Davis' 1991 trial, seven of the nine witnesses against him have recanted or contradicted their testimony. The U.S. Supreme Court ordered a district court in Savannah to review his claims of innocence in 2009, but District Judge William Moore ruled the following year that the evidence did "not require the reversal of the jury's judgment."

The parole board rejected a plea for clemency on Tuesday. In Georgia, only the board -- not the governor -- has the right to grant clemency.

And a request that Davis be allowed to sit for a polygraph by his attorneys was also rejected by the state Department of Corrections.