In a blow to Robert Blake's (search) defense, a judge ruled Thursday the actor's lawyer can't present jurors a theory that others, including the star prosecution witness, conspired to kill Blake's wife.

Superior Court Judge Darlene Schempp also made it clear she was barring any effort by attorney M. Gerald Schwartzbach to link Marlon Brando's (search) son, Christian, to the 2001 killing of Bonny Lee Bakley (search).

"I've found there was no link, direct or circumstantial, with Mr. Brando," she said. "It's pure speculation."

The judge had already ruled out as evidence a tape recording of a phone call between Brando and Bakley in which he told her she was lucky someone didn't put a bullet through her head. He was angry because Bakley had wrongly led him to believe he was the father of her child, when in fact Blake was.

Schempp said Schwartzbach will be blocked from asking witness Ronald "Duffy" Hambleton whether he conspired to kill Bakley on behalf of Christian Brando.

But she added, "I think I will allow a question such as, did you orchestrate this killing on behalf of someone else."

The judge acted after prosecutor Shellie Samuels argued the defense had presented no evidence to support its theory that Hambleton, a former stuntman, conspired with an assortment of characters to kill Bakley after speaking with Brando.

Schwartzbach told the judge her ruling to bar evidence of a motive by Hambleton to lie is a potentially reversible error on appeal.

"But that doesn't mean very much to a 71-year-old man," he said of Blake, who sat at the counsel table.

Schempp said a commissioner will begin screening prospective jurors Monday, and that jury selection will begin Nov. 15. The trial is expected to last four months.

Blake has pleaded not guilty to murdering Bakley, 44, whom he married after DNA testing showed he was the father of her baby, Rosie.

Blake told police he found his wife shot in their car after he went back into the restaurant where they had just dined to retrieve a gun he carried for protection.