BOISE – The Idaho Supreme Court on Friday rejected an appeal by a double murderer who claimed his death sentence should be voided because it’s unconstitutional to execute inmates deemed mentally retarded.

Gerald Pizzuto Jr., 52, was convicted and sentenced to die in 1986 for beating to death a Marsing, Idaho, woman and beating and shooting her nephew as they were prospecting north of McCall, Idaho.

Last fall, Pizzuto’s attorney filed a motion appealing a lower court ruling dismissing his claim that the death sentence should be reversed because he was clinically mentally retarded at the time of the slayings.

Federal Public Defender Joan Fisher argued that during a pre-sentence investigation, a physician testified that Pizzuto scored 72 on an IQ test and could not anticipate the consequences of his actions.

The U.S. Supreme Court ruled in 2002 that it is unconstitutional to execute anyone who fits the medical definition of mentally ill. One standard in Idaho code for defining mental retardation is an IQ of 70 or below, according to the opinion.

Because Pizzuto sought to apply that law retroactively to his case, Idaho law requires that he prove he was mentally retarded at the time of the crimes, when he was 29, and that the retardation occurred before his 18th birthday. A lower court dismissed Pizzuto’s claim in 2003, ruling his appeal was untimely and failed to prove his mental retardation claims.

In a unanimous opinion issued Friday, the justices agreed.

“One requirement of proving mental retardation is that Pizzuto had an IQ of 70 at the time of the murders and prior to his 18th birthday,” the justices wrote. “He did not offer any expert opinion showing that he did.”

Pizzuto was convicted of killing Berta Herndon, 58, of Marsing, and 37-year-old Del Dean Herndon, of Moresfield Neb.