By Bill Rankin

A Chatham County judge on Tuesday signed a death warrant for Troy Anthony Davis, who was convicted of killing a Savannah police officer in 1989.

The warrant sets the execution between Sept. 21 and Sept. 28. The state Department of Corrections will set the actual date. Davis has been on death row for 19 years.

Davis' appeals are exhausted. He is expected to once again ask the Georgia Board of Pardons and Paroles to grant him clemency. The board has previously denied that request.

Davis, 41, was convicted of killing off-duty police Officer Mark Allen MacPhail 21 years ago as MacPhail ran to the aid of a homeless man being pistol-whipped outside a Burger King.

The case has attracted international attention because a number of key prosecution witnesses either recanted or backed off their trial testimony. Other witnesses have come forward and said another man at the scene told them he was the actual killer.

In August, a federal judge emphatically rejected Davis' claims that he was wrongly convicted. In a 172-page order, U.S. District Judge William T. Moore Jr. said Davis failed to prove his innocence during an extraordinary hearing in June ordered by the U.S. Supreme Court.

MacPhail, 27 and a father of two, was gunned down before he could draw his weapon. After the killing, Sylvester "Redd" Coles went to the police with his lawyer and told them he and Davis were at the scene. At trial, he testified he was fleeing the scene when shots were fired, leaving Davis as the culprit. Coles denied being the triggerman.

At the June hearing, Davis' lawyers wanted to call witnesses who had given sworn statements that Coles had told them after the trial he was the actual killer. But Moore did not allow these witnesses to testify because Davis' lawyers did not subpoena Coles to testify. If they had, the judge said, he could have tested the validity of Coles' alleged confessions.

If Coles had in fact confessed to these witnesses, Moore suggested there could be an explanation --"he believed that his reputation as a dangerous individual would be enhanced if he took credit for murdering Officer MacPhail." Davis failed to prove the alleged confessions were truthful, Moore noted.

Of the seven witnesses Davis' legal team say recanted their trial testimony, "only one is a meaningful, credible recantation." The value of this recantation -- given by a jailhouse snitch who testified Davis told him he killed MacPhail -- is diminished because it was already clear the witness testified falsely at trial, the judge said.

Moore answered one question posed to him by the U.S. Supreme Court. He found that executing an innocent person would violate the Eighth Amendment's ban against cruel and unusual punishment.

"However, Mr. Davis is not innocent," the U.S. district judge wrote in August.

Chatham County Superior Court Judge Penny Freesemann signed the death warrant Tuesday.