Kristen Salchow, an attorney for the Georgia Resource Center, which has participated in Hill's defense, told CNN the 11th U.S. Circuit Court of Appeals granted the stay less than an hour before Hill was to be executed by lethal injection at a state prison in Jackson.
Hill, whose defense team says is mentally disabled with an IQ of 70, was serving a life sentence for the 1985 murder of his girlfriend, Myra Wright, when he killed a fellow Georgia state prison inmate, Joseph Handspike, in 1990.
Defense lawyers have argued Hill should not be executed, citing a 2002 U.S. Supreme Court ruling that executing mentally retarded people constitutes cruel and unusual punishment in violation of their Eighth Amendment rights under the U.S. Constitution.
Several state courts in Georgia have decided the rule does not apply in Hill's case because state law requires inmates to prove mental impairment "beyond a reasonable doubt," CNN said.