The court in New Orleans ruled about two hours before Robert James Campbell was scheduled to die Tuesday.
The execution would have been the first in the United States since the botched lethal injection of Clayton Lockett in Oklahoma. The court had already rejected an appeal based on Texas's law withholding the identities of the suppliers of execution drugs, and his lawyers had taken that argument to the U.S. Supreme Court.
Campbell's lawyers charged that Texas withheld information about his intellectual disability, while lawyers for the state argued that he had had ample time to raise the issue. The Fifth Circuit judges, in a unanimous decision, appeared to side with Campbell.
"It is regrettable that we are now reviewing evidence of intellectual disability at the eleventh hour before Campbell's scheduled execution," the court said. "However, from the record before us, it appears that we cannot fault Campbell or his attorneys, present or past, for the delay."
The Supreme Court ruled in 2002 that inmates with severe intellectual disability -- generally defined as testing at 70 or lower -- cannot be executed. Campbell's IQ scores have ranged from 68 to 71.
Campbell, 41, was sentenced to death for kidnapping, robbing, raping and killing a young bank teller, Alexandra Renton, in Houston in 1991.