On Wednesday, the Georgia State Board of Pardons rejected a last-minute appeal to halt the execution of Troy Davis, a death row inmate convicted of shooting and killing a police officer in a crime both he and many others say he did not commit.

Although defense attorneys argued that ballistic testing linking Davis to the shooting was flawed and said Davis would take a polygraph test, the board said it would not review its decision to allow the execution by lethal injection, scheduled for 7 p.m. Wednesday night, to go forward.

Benjamin Jealous, head of the NAACP, said Davis' family is "heartbroken" and stunned "that the state of Georgia would kill their loved one."

But the family of Mark MacPhail, the policeman killed in the 1989 shooting, expressed relief. "Justice was finally served for my father," Mark MacPhail Jr. said. "The truth was finally heard."

Davis' case has received worldwide attention from people such as Pope Benedict XVI and former  President Jimmy Carter. In addition, the NAACP, Amnesty International, ColorOfChange.Org and Change.org collected more than 900,000 signatures on a petition asking the pardon board to spare his life.

Six retired corrections officials also sent a letter to Georgia corrections officials and Gov. Nathan Deal asking them to urge the pardons board to reconsider its decision.

"While most of the prisoners whose executions we participated in accepted responsibility for the crimes for which they were punished, some of us have also executed prisoners who maintained their innocence until the end. It is those cases that are most haunting to an executioner," the letter said.