An appeals court in the US state of Georgia on Tuesday delayed the execution of a mentally disabled man with just minutes to spare, his lawyer said.
The US Supreme Court had earlier rejected a final appeal in the case of Warren Hill, a 52-year-old African American with a reported IQ of 70, who has spent the last 21 years on death row for killing a fellow inmate.
His planned execution has drawn protests from rights activists and mental health advocates calling the sentence a miscarriage of justice.
The Supreme Court ruled against the execution of prisoners with mental disabilities in 2002, but left each state with the authority to determine what constitutes mental disability.
Georgia has the strictest standard of any US state, with courts requiring "proof of retardation beyond a reasonable doubt" -- a burden that some mental health professionals say is almost impossible to meet.
A Georgia court earlier agreed with an appeal by Hill's lawyers, but was then overruled by a higher court in the state, which found that Hill could not prove his retardation beyond a reasonable doubt.
In the latest appeal, Hill's lawyers had asked the court to grant them another opportunity to prove he is ineligible for execution.
"Each of the state witnesses who previously testified that he is not mentally retarded has since repudiated his earlier opinion and now agrees with Mr. Hill's experts that Mr. Hill satisfies Georgia's criteria for finding him mentally retarded," they wrote.
If Hill had been put to death as scheduled, at 7:00 pm local time (0000 GMT), it would have been the first death penalty to have been carried out in Georgia since the controversial 2011 execution of Troy Davis.
Davis was executed on September 21, 2011, for a 1991 murder conviction despite a lack of physical evidence tying him to the crime and the resulting reliance on eyewitness testimony, much of which was later changed or recanted.
Former US president Jimmy Carter, Archbishop Desmond Tutu and Pope Benedict XVI had all weighed in on his behalf in a racially charged case that spanned two decades, becoming a cause celebre for death penalty opponents.