In a last minute appeal for clemency, death-row inmate Troy Davis is asking the Georgia parole board to spare his life.
He is scheduled to be killed by lethal injection in Jackson, Georgia, Wednesday, after being convicted of the murder of an off-duty policeman in 1989.
Davis, 42 has had three brief reprieves from execution after doubts appeared over his conviction.
In 1991 he was convicted of murdering Mark MacPhail, who was working as a security guard at a restaurant in Savannah when he intervened in an argument in a parking lot and was shot dead.
However since the conviction many of the witnesses have changed their testimony and there is no clear physical evidence linking him to the scene.
According to a report by AFP, groups supporting Davis say close to 1 million people world-wide have signed petitions calling for clemency, with petitions last week delivered to state authorities containing about 650,000 signatures.
His high profile supporters include former US president Jimmy Carter, Pope Benedict XVI and US actress Susan Sarandon, as well as the National Association for the Advancement of Colored People, and Amnesty International.
The five-member parole board will issue a simple majority decision on Wednesday which is believed to be the man’s final chance at life.
Since 1976 Georgia has executed 51 people convicted of murder with clemency granted on only seven occasions.
The victim’s family have maintained that Davis is the killer and that he should be executed.