Some experts and advocates for mentally disabled people are urging Gov. Timothy M. Kaine to spare the life of Kevin Green, set to be executed Tuesday.

In a seven-page letter to the governor, advocacy groups say they believe Green is mentally disabled and "request you to exercise your discretion to grant clemency in this case, and to commute Kevin Green's sentence to a sentence of life in prison."

In 2002, the U.S. Supreme Court barred the execution of killers who are mentally disabled. No state or federal court, however, has agreed that Green is mentally disabled, so his lawyers have filed a clemency petition with Kaine.

Meanwhile yesterday, Green's lawyers asked the U.S. Supreme Court to halt his execution while the justices consider taking up his appeal on other legal issues.

Green, 31, was sentenced to death for the Aug. 21, 1998, slaying of Patricia L. Vaughan, 53, shot four times as she worked at Lawrence's Grocery, a small business she and her husband, Lawrence T. Vaughan, operated in rural Brunswick County.

Lawrence Vaughan, shot twice during the robbery, said recently that he and the couple's two daughters plan to attend the execution, set to take place at 9 p.m. at the Greensville Correctional Center, unless the U.S. Supreme Court or Kaine intervenes.

The family does not believe Green is mentally disabled.

Under Virginia law, an inmate must prove the retardation was present prior to age 18, must have an IQ score of 70 or below, and have significant limitations in adaptive skills for everyday functioning.

Green was tried in 2001. The jury heard an expert say Green was mentally disabled, but another expert said Green had a personality disorder and was pretending to be less intelligent than he is.

The Virginia Supreme Court dismissed his retardation claim as "frivolous." A federal magistrate judge who conducted a hearing found that Green's IQ was below 70. However, while finding that Green had some limitations, he said they were not sufficiently significant.

Among other things, the magistrate said that there was evidence Green had a savings account, paid his own rent, bought money orders, profited from drug deals, obtained a driver's license and hid much of his criminal activities from his parents.

The U.S. District Court judge and later a federal appeals court dismissed his retardation claim.

In their letter to Kaine, James W. Ellis, past president of the American Association on Mental Retardation, and the executive directors of ARC of Virginia, ARC of the United States and the American Association on Intellectual And Developmental Disabilities said the magistrate judge erred by balancing Green's developmental strengths and deficits.

They contend that only Green's deficits should have been considered: "One of the central truths about mental retardation is that people who have the disabilities vary widely in their skills and abilities."

"Green clearly has substantial deficits in adaptive behavior," they wrote, saying there was detailed evidence Green could not sign his name, read a newspaper or tell stories coherently, and that he needed help paying bills and was easily tricked out of his money.

Kaine spokesman Gordon Hickey said he could not comment on the clemency petition. Kaine let the July 20, 2006, execution of Brandon Wayne Hedrick go forward, though his lawyers said there was some evidence he was mentally disabled.

Contact Frank Green at (804) 649-6340 or fgreen@timesdispatch.com.