Robert Wayne Holsey scheduled to die Tuesday evening in Georgia

ATLANTA, Dec. 9 (UPI) -- The Georgia Board of Pardons and Paroles has refused to grant clemency to Robert Wayne Holsey, leaving his execution for killing a police officer on track for Tuesday.

Unless a court intervenes, Holsey will die by lethal injection at 7 p.m. in the state prison in Jackson. His lawyers have asked the state Supreme Court to stop the execution arguing that Georgia's standard for determining whether a death row inmate is intellectually disabled violates U.S. Supreme Court rulings.

Holsey was sentenced to death in 1997 for killing Baldwin County Sheriff's Deputy Will Robinson after robbing a Milledgeville convenience store in 1995. His lawyer at the trial, since disbarred, has admitted he was drinking a quart of vodka a day at the time and should not have been representing anyone.

Monday's hearing focused on Holsey's childhood, with testimony from a sister who described the physical abuse he received, and on his conduct in prison, a lawyer, Brian Kammer, told the New York Times. A prison chaplain and a former guard described him as a well-behaved prisoner who tried to calm others down.

The hearing was closed to the news media and public.

Georgia, unlike any other state, requires lawyers for inmates claiming intellectual disability to prove it beyond a reasonable doubt.

In May, the U.S. Supreme Court, having already found the execution of the intellectually disabled unconstitutional, ruled there cannot be "an unacceptable risk that persons with intellectual disability will be executed." The court, in a Florida case, struck down the use of IQ tests as the only standard, with an IQ of 70 the typical cutoff.

Kammer argues the Georgia law violates that decision. In Holsey's case, the state argues that he could function -- for example, he could drive a car. He used a car in the 1995 robbery and shot Robinson when the deputy pulled him over after the robbery.