It looks like death row inmate Warren Hill is now out of options for avoiding execution.

The U.S. Supreme Court decided today that it would not consider a petition from Hill’s lawyer, Brian Kammer, to admit evidence of his mental retardation, which would have protected him because of a 2002 Supreme Court ruling that says it's unconstitutional for states to execute the mentally retarded.

Kammer released the following statement:

We are gravely disappointed that the U.S. Supreme Court has failed to act to ensure the protection for persons with intellectual disability that was promised by the Court’s 2002 ruling in Atkins v. Virginia.

It is the unanimous opinion of all doctors who have examined him that Mr. Hill is a person with mental retardation. However, Mr. Hill has been procedurally barred from proving his exemption from capital punishment, which is why he brought his case to the U.S. Supreme Court, in the hopes that the Court would ensure that the evidence of his intellectual disability would be heard.

It is tragic that our highest court has failed to enforce its own command that persons with mental retardation are categorically ineligible for the death penalty.

On July 15, Hill received an indefinite stay of execution—hours before he was to be executed—from Fulton County Superior Court Judge Gail Tusan after his lawyer won a motion challenging Georgia's "Lethal Injection Secrecy Act."

That stay of execution is still in effect until the Georgia Supreme Court rules on whether or not the law—which classifies the knowledge of where drugs used in executions come from as a state secret— violates Hill's Eighth Amendment right against cruel and unusual punishment.

Kammer argued that it left questions as to the purity of the lethal injection chemicals, which could ultimately pose unjust harm during the execution process.

Hill was convicted of killing his girlfriend in 1986 and has been on death row since 1990 for the murder of a fellow inmate. Three state psychologists who intially examined him, saying that he was of sound mind, have since recanted and now claim that he fits the description for mental retardation.