The planned executions of 2 death row inmates Warren Lee Hill and Andrew Cook, scheduled to take place this week, were halted due to challenges to Georgia lethal injection procedures.

Cook, the son of a former FBI agent, was found guilty of murder in the 1995 shooting deaths of Grant Hendrickson and Michele Cartagena.

Lawyers for both Cook and Hill argued that the state of Georgia is violating state law by using the chemical 'pentobarbital' in executions without a prescription.

Hill, a 52 year-old Georgia man, killed fellow prisoner 1990. Hill's execution was stayed on Tuesday as he was being prepared for lethal injection. In addition to procedural violations, the stay was granted so that courts could consider claims that Hill was mentally disabled.

In 2-1 decision, a panel on the 12^th U.S. Circuit Court of Appeals said that because doctors changed their minds about Hill's mental capacity, further review is needed.

The majority judges explained, "In other words, all of the experts - both the State's and the petitioner's - now appear to be in agreement that Hill is in fact mentally retarded."

Earlier that day, the state parole board, the Supreme Court of Georgia and the U.S. Supreme Court had all declined to stop the execution.

Hill was sentenced in 1990 for beating his fellow inmate Joseph Handspike to death. He reportedly used a board studded with nails to beat Handspike while he slept and other prisoners begged Hill to stop.

When he committed the prison murder, he was already serving a life sentence for murdering his girlfriend, Myra Wright, who he had shot 11 times.

In an email to the Associated Press, defense attorney Brian Kammer said, "We are greatly relieved that the Eleventh Circuit Court of Appeals has stayed the execution of Warren Hill, a person with mental retardation. All the doctors who have examined Mr. Hill are unanimous in their diagnosis of mental retardation."

In Georgia, defendants facing the death penalty have to prove that they are mentally disabled beyond a reasonable doubt to avoid executions. This strict standard has been upheld multiple times in state and federal courts.