A jury in the US state of Virginia has decided that a man with learning difficulties on death row is intelligent enough to be executed.
Atkins will now be executed by lethal injection
Daryl Atkins has twice been sentenced to death for murder, but in 2002 won a Supreme Court ruling that the mentally retarded cannot be put to death.
However, the court said it was up to individual states to apply the ruling.
To escape execution in Virginia, an inmate has to prove he has an IQ of 70 or less; but Atkins scored 76 recently.
He had previously scored 59 in 1998.
The intellectual stimulation he got from constant contact with lawyers in the case is thought to have raised his IQ above the threshold of 70.
The jury considered a wide range of evidence to determine his mental capacity, including records from his childhood, various intelligence and memory tests and interviews with people who had known him as an adult.
The prosecution blamed his poor performance in school on the use of drugs and alcohol, and said the claim of mental retardation was a ploy to avoid execution, the Associated Press news agency reports.
Daryl Atkins has been sentenced to death in 1998 for murdering a 21-year-old Air Force mechanic in 1996 over beer money.
But in 2002 his case led the Supreme Court to ban the death penalty for the mentally retarded, while leaving it up to individual states to decide who is covered by the ruling.
He is now due to be executed in December by lethal injection.