ATLANTA (AP) — Lawyers for a Georgia inmate scheduled to be executed next week said Monday they have filed papers asking a federal appeals court for a delay until the U.S. Supreme Court weighs in.

Last week, the state scheduled Warren Lee Hill's execution for July 15. But his lawyers, who have long claimed Hill is mentally disabled and therefore shouldn't be executed, had asked the Supreme Court in May to review his case in light of new evidence they submitted.

The execution of mentally disabled offenders is prohibited by state law and a 2002 U.S. Supreme Court decision.

Three state experts who testified in 2000 that Hill was not mentally disabled issued sworn statements in February saying they were rushed in their original evaluation, that they now have more experience and that there have been scientific developments since. All three reviewed facts and documents in the case and write that they now believe Hill is mentally disabled.

The state has repeatedly said Hill's lawyers failed to prove beyond a reasonable doubt that Hill is mentally disabled, and has previously dismissed the new doctor statements. The attorney general's office had no comment on Hill's filing Monday.

The Supreme Court is currently scheduled to consider whether to take up Hill's case on Sept. 30, his lawyers said in a court filing Monday. They urge the 11th U.S. Circuit Court of Appeals to delay his execution until the high court proceedings have run their course.

Hill was sentenced to death for the 1990 beating death of fellow inmate Joseph Handspike. Hill bludgeoned Handspike with a nail-studded board while his victim slept, authorities said. At the time, Hill was already serving a life sentence for the 1986 slaying of his girlfriend, Myra Wright, who was shot 11 times.

Hill has come within hours of death twice in the past year before scheduled executions were halted by last-minute court orders.

A three-judge panel of the 11th Circuit in February temporarily stayed Hill's execution to give him a chance to argue that a federal court should reconsider his case based on the new statements by mental health experts. But the panel later ruled Hill was procedurally barred from submitting his case to a federal court for reconsideration. But the 11th Circuit judges said Hill could still turn to the U.S. Supreme Court directly.

The state's supply of the execution drug pentobarbital expired in March, and the drug has become increasingly difficult for states to get since the manufacturer has said it doesn't want the drug used in executions. A Department of Corrections spokesman said in an email that the state does not currently have any execution drugs, but he has previously said the state expects to get some of the drug by the scheduled execution date.