( CNN ) -- The U.S. Supreme Court on Thursday upheld a 30-day stay of execution for condemned Georgia murderer Warren Lee Hill , whose attorneys say he 's mentally disabled . Georgia had asked the justices to lift the stay , which was granted minutes before Hill had been scheduled to die by lethal injection Tuesday night . A federal appeals court in Atlanta halted the execution to give lawyers a month for written arguments on whether Hill should be spared under the federal ban on executions of the mentally disabled . Georgia law requires inmates to prove mental retardation `` beyond a reasonable doubt '' to avoid the death penalty -- the highest standard of any state . State prosecutors say Hill has repeatedly failed to meet that standard in years of appeals . But three doctors who examined Hill for the state have reversed their conclusions and now say he should be spared , giving fresh ammunition to Hill 's attorneys . That reversal `` establishes consensus among every doctor who has evaluated Mr. Hill that he is mentally retarded , '' his lawyer , Brian Kammer , said Thursday . Hill 's defenders say he has an IQ of 70 . He was sentenced to death for the 1990 killing of Joseph Handspike , another inmate in a Georgia state prison . Hill was already serving a life sentence in the 1985 killing of his girlfriend , Myra Wright , when he beat Handspike to death with a nail-studded board . Tuesday 's reprieve was his second in less than a year .
CNN has refused to overturn Hill Tuesday night stay . Warren Hill 's had been scheduled to die by lethal injection last-minute . His lawyers say he is mentally disabled and should be spared . Prosecutors say his claim has n't survived court scrutiny .