Twice-convicted killer Warren Lee Hill was granted a last-minute stay of execution on Tuesday evening, a staff attorney for the Georgia Resource Center told CNN.
The 11th U.S. Circuit Court of Appeals granted the stay, which came within an hour of when Hill was scheduled to be executed, said attorney Kirsten Salchow. The Georgia Resource Center has been involved in defending Hill.
Hill, whose supporters say is mentally disabled, was sentenced to death for the 1990 killing of Joseph Handspike, another inmate in a Georgia state prison.
The execution had been scheduled for 6 p.m. CT Tuesday at a state prison in Jackson, about 45 miles south of Atlanta.
Hill was convicted of beating Handspike to death with a nail-studded board while serving a life sentence in the 1985 killing of his girlfriend, Myra Wright.
Lawyers for Hill argue that his IQ of 70 means he should be spared under the 2002 decision that barred the execution of the mentally disabled. But a string of state courts has said Hill doesn't qualify under Georgia law, which requires inmates to prove mental impairment "beyond a reasonable doubt."
Georgia is the only state with the reasonable-doubt standard, which Hill's lawyers call "a virtually insurmountable barrier" that flies in the face of the justices' 2002 decision.
"The U.S. Supreme Court says we don't put mentally retarded people to death, but we'll let the states determine who's retarded and who's not," CNN legal analyst Paul Callan said Monday.
Handspike's family has called for the execution to be called off, as have former classmates and school officials. The Georgia Council on Developmental Disabilities has weighed in against the execution, stating, "No other state risks the lives of those with developmental disabilities to this extreme."
Three doctors who examined Hill for the state "have now revised their opinions and find that Mr. Hill does meet the criteria for mental retardation," his lawyers argued in court papers.
But lawyers for the state argued that Hill had served in the Navy, held a job and managed his money before Wright's killing – signs that while he had a low IQ, he didn't necessarily meet the legal standard for retardation.
Hill had been scheduled for execution in July, but the state Supreme Court halted the execution on procedural grounds.
(CNN's Tom Watkins, Matt Smith, Bill Mears, Dana Ford and Dave Alsup contributed to this report.)