Davis is scheduled to die Wednesday at 7 p.m. EDT by injection for killing off-duty Savannah officer Mark MacPhail, who was shot dead while rushing to help a homeless man being attacked. It is the fourth time in four years that Davis' execution has been scheduled by Georgia officials.
The decision appeared to leave Davis with little chance of avoiding his execution date. Defense attorney Jason Ewart has said that the pardons board was likely Davis' last option, but he didn't rule out filing another legal appeal.
"Justice was finally served for my father," said Mark MacPhail Jr., who was an infant when his father was gunned down. "The truth was finally heard."
Kim Davis, the inmate's sister, declined immediate comment on the decision.
Georgia's State Board of Pardons and Paroles said it considered "the totality of the information presented" before deciding to deny clemency.
"The Board members have not taken their responsibility lightly and certainly understand the emotions attached to a death penalty case," the five-person panel said in a statement.
The board's statement noted that it has commuted three death penalty sentences since 2000 and "thoroughly deliberated" the Davis case.
Davis' lawyers have long argued Davis was a victim of mistaken identity. But prosecutors say they have no doubt that they charged the right person with the crime.
MacPhail was shot to death Aug. 19, 1989, after coming to the aid of Larry Young, a homeless man who was pistol-whipped in a Burger King parking lot. Prosecutors say Davis was with another man who was demanding that Young give him a beer when Davis pulled out a handgun and bashed Young with it. When MacPhail arrived to help, they say Davis had a smirk on his face when he shot the officer to death.
The Rev. Al Sharpton, who plans a noon EDT vigil at the state prison in Jackson on Wednesday, said he's asking his supporters to urge the pardons board to reconsider. And he is also asking Chatham County District Attorney Larry Chisolm to block the execution.
"This is probably the most egregious injustice I have seen in a long time, to set a precedent that a man can be executed when the evidence against him has mostly been recanted," said Sharpton. "It's unthinkable."
Chisolm has said it's unlikely he will seek to intervene.
"What stands between the defendant and execution is the Board of Pardons and Paroles," Chisolm said on Friday. "And I think whatever decision they make in the case will probably be the final decision."
Davis has captured worldwide attention because of the doubt his supporters have raised over whether he killed MacPhail. Several of the witnesses who helped convict Davis at his 1991 trial have backed off their testimony or recanted. Others who did not testify say another man at the scene admitted to the shooting.
The U.S. Supreme Court even granted Davis a hearing last year to prove his innocence, the first time it had done so for a death row inmate in at least 50 years. But in that June 2010 hearing, Davis couldn't convince a federal judge to grant him a new trial. The Supreme Court did not review his case. Federal appeals courts and the Georgia Supreme Court have upheld his conviction, leaving the parole board as his last chance.
MacPhail's relatives said they were relieved by the decision. "That's what we wanted, and that's what we got," said Anneliese MacPhail, the victim's mother. "We wanted to get it over with, and for him to get his punishment."
Amnesty International USA director Larry Cox called the pardon board's decision "unconscionable."
"Should Troy Davis be executed, Georgia may well have executed an innocent man and in so doing discredited the justice system," Cox said.
Amnesty International and the National Association for the Advancement of Colored People have scheduled an 11 a.m. EDT press conference on the case and a 7 p.m. demonstration on the steps of the Georgia Capitol.
Among those who supported Davis' clemency request are former president Jimmy Carter and Pope Benedict XVI. A host of conservative figures have also advocated on his behalf, including former U.S. Rep. Bob Barr, ex-Justice Department official Larry Thompson and one-time FBI Director William Sessions.
Davis' legal team said in a statement it was "incredibly disappointed" by the board's decision.
"The death penalty should not be exercised where doubt exists about the guilt of the accused. The Board did not follow that standard here," their statement said. "The state's case against Mr. Davis, based largely on discredited eyewitness testimony and an inaccurate ballistics report, cannot resolve the significant, lingering doubts that exist here."
Associated Press writer Kate Brumback in Atlanta contributed to this story.