Does an attorney who handles his own case have a fool for a client? Common wisdom says so, but best-selling British novelist and playwright Jeffrey Archer asked his mother. After all, he was only 11 years old at the time.

"My mother had taken me to see 'Witness for the Prosecution' with Charles Laughton--and I had fallen in love with it," Archer said recently from London, where his own courtroom drama, "Beyond Reasonable Doubt," is still running after three years and more than 1,000 performances. The U.S. premiere opens tonight in a production by the Laguna Playhouse.

Recalling the long-ago moment that spurred him to query his mother, the 49-year-old writer said he began to wonder what would happen if a renowned defense lawyer were accused of murdering his wife.

"I was suddenly fascinated by the idea of whether a Clarence Darrow figure or a barrister of that stature would call someone in," he said, "or whether he would defend himself. And I've been fascinated ever since."

Though his mother didn't have an answer, "Beyond Reasonable Doubt"--Archer's first produced play--provides his answer, and also explains who killed the barrister's wife. Not least, it proves that Archer certainly was no fool for asking the question. Royalties from the play have come to "a million dollars," he said.

Besides the London version in the West End, professional productions have also been staged in Canada, South Africa, Australia, New Zealand and Hong Kong. The Playhouse version--at the Moulton Theatre in Laguna Beach through April 8--is an amateur offering.

"We would love to have had a professional production in the States, but we haven't had an offer," Archer said.

Not that he was complaining. Next to his earnings from half a dozen blockbuster novels, theatrical royalties don't figure nearly as strongly in his bank deposits.

"There's no comparison," Archer said.

"Kane and Abel," his 1980 saga about old money and new Americans, has topped 250,000 hardback copies and 4 million in paperback. It was made into an eight-hour NBC miniseries. With "The Prodigal Daughter," his 1982 tale about America's first woman President, he became the first British writer to reach sales of a million copies in a single year. And "First Among Equals," his 1984 chronicle about the House of Commons, ranked high on the New York Times bestseller list for 24 weeks. That novel, too, was made into a TV miniseries.