The U.S. Supreme Court granted a stay tonight less than an hour before a man convicted of robbing and killing a Cumberland County couple was scheduled for execution.

The justices agreed to hear the appeal of Michael Wayne Williams, who had been scheduled to die by injection at 9 p.m. at the Greensville Correctional Center here.

Williams, 31, was sentenced to die for the February 1993 slayings of Morris Keller Jr., 45, and his wife, Mary Elizabeth Keller, 34, in Cumberland County. Williams was later sentenced to life in prison for each of four murders committed in Prince Edward County in December 1992.

In a final appeal, attorneys for Williams argued that his constitutional rights were violated when the prosecutor used the fact that he had heard other witnesses' testimony to impeach his testimony.

However, the appeal was granted based on a second issue raised by the appeal--that Williams was denied a federal evidence hearing on claims the state suppressed facts and that he was denied discovery requests and investigative resources during state court proceedings.

Barbara Hartung, one of Williams's attorneys, said the high court agreed to review a portion of a 1996 federal law that restricts a U.S. district court's ability to conduct evidentiary hearings. "It will affect a lot of people," she said.

David Botkins, a spokesman for state Attorney General Mark L. Earley (R), said several relatives of Williams's victims had gone to Jarratt to witness the execution.

"It's unfortunate at this particular juncture that the victims' family members have to relive the horror of the last few years," Botkins said. He said the state will argue vigorously to uphold the death sentence.

Williams was notified of the stay about 8:10 p.m., said Larry Traylor, a Department of Corrections spokesman.

The Rev. Bob West, a chaplain who was with Williams when he got the news by telephone from Hartung, said the inmate was "elated."

"All of a sudden, he said, 'I've got a stay. Praise God,' " West said.

Williams was convicted in January 1994 of capital murder in the Kellers' deaths, along with burglary, rape, arson, two counts of robbery and two counts of abduction. Accomplice Jeffrey Alan Cruse testified against Williams and received a life sentence.

According to a Virginia Supreme Court summary of the case, Cruse and Williams locked the Kellers in a closet, and both men raped Mary Keller after searching the house for valuables. After marching the couple to a wooded area, Williams shot Morris Keller, and Cruse shot Mary Keller.

Williams shot Morris Keller again after the victim got up and then shot both victims several more times, according to the summary. The pair then set fire to the house and drove to Fredericksburg, where they sold property stolen from the house.

At Williams's trial, both men admitted to firing one shot but blamed the other shots on each other.

Williams did not seek clemency from Gov. James S. Gilmore III (R). Hartung declined to say why.

Williams would have been the 13th person executed in Virginia this year and the 72nd since the U.S. Supreme Court allowed the death penalty to resume in 1976.

The Supreme Court's stay of execution for Michael Williams was its second this year in a Virginia execution.

In March, the court granted a stay to condemned killer Terry Williams and said it would take up his appeal. Terry Williams, who has been on death row for 13 years, was convicted of murdering an elderly Danville man. His appeal, which will probably be argued next year, involves a claim that he was denied adequate legal help at his sentencing.