The U.S. Supreme Court yesterday turned down a third appeal aimed at stopping the execution of James D. Briley who was convicted of murdering a Richmond woman and her son in a 1979 crime spree that left 11 people dead.

Briley, 29, is scheduled to be executed April 18, six months after his older brother, Linwood, died in Virginia's electric chair. James, Linwood and a third brother, Anthony, were involved in a series of brutal murders in the Richmond area. Anthony, who was 16 when he was arrested in 1979, is serving a 109-year prison sentence.

The two elder Briley brothers participated in the largest death row escape in U.S. history last year when six inmates broke out of the Mecklenburg Correctional Center in southern Virginia. The Brileys, the last to be recaptured, were arrested in Philadelphia almost three weeks after the escape.

The appeal turned down yesterday by the Supreme Court did not challenge Briley's convictions, but asserted that he had had inadequate legal counsel for his trial and that jurors were not given "a clear explanation" of how to go about determining whether a death sentence or life in prison would be the more appropriate punishment for the crimes.

Briley's Richmond attorney, Gerald Zerkin, said "it is a little early to decide what to do next," adding, "the further up you go, the less likely you are going to be successful" in the appeals process.

Briley was sentenced to death for murdering Judy Barton and her 5-year-old son, Harvey, in their Richmond home.

Zerkin said that Briley's recent transfer from Mecklenburg to the State Penitentiary in Richmond to await execution may jeopardize his plans to marry a North Carolina woman who says she will write a book about Briley.

The marriage had been scheduled for this week in Mecklenburg. Zerkin said the warden at the state prison in Richmond will have major control over whether the ceremony will be allowed. Evangeline Grant Redding of Oxford, N.C., a former television personality, said she wants to marry Briley "to give me credibility to fight for him."