(CNN) -- Religious leaders called Thursday on their peers to join them in seeking clemency for a man on Georgia's death row, citing doubts about whether he is guilty.
People of Faith Against the Death Penalty and Amnesty International said they were asking religious leaders to encourage others to sign a public letter (troyletter.org) asking the Georgia Board of Pardons and Paroles to commute the death sentence of Troy Davis, 42. As of Thursday night, more than 1,600 people from across the country had done so.
"This is a matter of conscience and it is urgent," said Stephen Dear, executive director of People of Faith Against the Death Penalty, a national advocacy group based in North Carolina.
"We call on religious leaders, regardless of their position on the death penalty, to use their moral authority to help stop the execution of a man with a strong case of innocence."
Witnesses testified that Davis, then 19, and two others were harassing a homeless man in a Burger King parking lot in 1989 when off-duty Savannah, Georgia, Police Officer Mark Allen MacPhail went to the man's assistance. They testified that Davis shot MacPhail twice and fled.
Since Davis was convicted in 1991, seven of the nine original witnesses have recanted or changed their testimonies; no physical evidence links him to the crime.
Davis was granted a stay of execution by the U.S. Supreme Court two hours before he was to be put to death in 2008, and the court in 2009 ordered the federal district court to take another look at the case.
That court, after holding a hearing to review evidence, ruled that Davis "failed to show actual innocence" in the case. The district court suggested that, for procedural reasons, Davis should take his appeal of its ruling directly to the Supreme Court.
Davis ended up filing with both the 11th Circuit and the Supreme Court. The 11th Circuit deflected the appeal in November, saying it agreed with the district court that the Supreme Court was the correct place for the filing. Davis then took his case to the U.S. Supreme Court in January, filing two pleas.
One sought review of the Georgia federal judge's rejection of the innocence claim, and the other asked for a test of the 11th Circuit's refusal to review the case. The justices in March turned down both pleas without comment.
That means Davis could face a fourth execution date within two weeks, according to the letter. "Only the Georgia Board of Pardons and Paroles can stop his execution now," the release said.
"Pastors and ministers and imams and priests and rectors are reading about this case and they're researching it for themselves," Davis' sister, Martina Correia, told CNN Thursday. "They're having lots of problems with it and saying, 'Look, we've got to stop this. We're supposed to be a country of faith and a state of faith, but you're not willing to give somebody a fair chance."
Davis, who is being held at the Georgia Diagnostic and Classification Prison in Jackson, has not been allowed to speak to the news media, Correia said.
She said the case has already exacted a fatal toll on her family: Their 65-year-old mother died two weeks ago as she sat watching television. Earlier in the day, she had been reading a newspaper article that said her son might be the first prisoner in the state to be put to death with a new drug, Correia said. "That's the last thing she read."
Their father died in February 1992, six months after his 19-year-old son was sentenced to death. "He said that he couldn't watch them kill his son for something he didn't do, so he stopped taking his insulin," she said. "One day he just went into a diabetic coma. He didn't wake up."
But she said her brother has accepted that he may be executed if that helps focus attention on the inequities of the system.
"I just want people to know that this is not just for our family," Correia said Thursday in a telephone interview. "Because we dishonor Officer MacPhail by killing the wrong person. All we've wanted is fairness over finality."