Lawyers for Troy Davis, scheduled to die by lethal injection at 7pm local time, requested a polygraph for their client but prison officials turned them down, the lawyers were quoted by the Atlanta Journal-Constitution newspaper as saying.
Davis’s case has attracted international attention and an online protest that has accumulated nearly one million signatures because of doubts expressed in some quarters over whether he killed police officer Mark MacPhail in 1989.
Davis’ best hope of avoiding execution lay with the Georgia Board of Pardons and Paroles but on Tuesday it denied him clemency following a one-day hearing.
Supporters planned vigils around the world including outside Georgia’s death row prison in Jackson and at US embassies in Europe.
As well as calls for the polygraph test, his backers urged prison workers to strike or call in sick and posted a judge’s phone number online, urging people to call and ask him to put a stop to the execution.
They even considered a desperate appeal for White House intervention.
Davis’s supporters include former president Jimmy Carter and Pope Benedict XVI.
Several witnesses have recanted their accounts that it was Davis who pulled the trigger that fatally shot 27-year-old Mark MacPhail in 1989. Some jurors have said they have changed their minds about his guilt.
Still, prosecutors and MacPhail’s family have staunchly backed the verdict and state and federal courts have repeatedly upheld his conviction.
MacPhail was working security at a bus station on August 19, 1989, and rushed to the aid of Larry Young, a homeless man who prosecutors say Davis was bashing with a handgun after asking him for a beer.
When MacPhail got there, they say Davis had a smirk on his face as he shot the officer to death in a parking lot. Others have claimed the man with Davis that night has told people he actually shot the officer.
No gun was ever found, but shell casings were linked, prosecutors say, to an earlier shooting for which Davis was convicted.
Witnesses placed Davis at the crime scene and identified him as the shooter. No other physical evidence was found.
An upbeat Davis planned to spend his last few hours meeting with friends, family and supporters.