Robert Blake's (search) lawyer began chipping away at the credibility of a prosecution witness who hasn't even taken the stand yet by making reference to the man's possible drug use.

The subject of Gary McLarty, who claims Blake solicited him to kill the actor's wife, was brought up by defense attorney M. Gerald Schwartzbach during his cross-examination of a police detective Thursday.

Blake, 71, is charged with killing Bonny Lee Bakley (search), whom he married after learning he had fathered her child.

McLarty, who is expected to take the stand Monday, testified during a preliminary hearing that Blake approached him with an offer of $10,000 to kill Bakley.

Prosecutors claim that McLarty and another man refused to do the job and that Blake shot Bakley, 44, to death in May 2001 in a car outside a restaurant where she and the "Baretta" (search) actor dined.

Schwartzbach tried to show that investigators ignored the possibility that McLarty was under the influence of drugs when he gave them incriminating statements.

"Did you ask Mr. McLarty if he was using cocaine in 2001?" Schwartzbach asked Ronald Ito.

"I don't believe I did," the detective replied.

At one point the prosecutor tried to insinuate that Blake used drugs. But on cross-examination Ito acknowledged that Blake was in Alcohol Anonymous for years and had not used drugs during the time he knew Bakley.

Questioning also revisited the involvement of the late actor Marlon Brando's son, Christian, in the Blake case.

Ito said that in the weeks after Bakley was murdered he received a telephone tip that Christian Brando had a connection to the killing but it turned out to be unsubstantiated. He said members of his team flew to Washington state to interview Brando and his alibi for the time of the killing was verified.

Brando had a relationship with Bakley and at one time she told him he was the father of her baby, a child which tests ultimately showed was fathered by Blake.