SANTA MONICA, CALIF., JAN. 4 -- With their star witness in Tahiti and their murder case in shambles, Los Angeles County prosecutors today struck a plea bargain with actor Marlon Brando's eldest son, who pleaded guilty to voluntary manslaughter in the killing of his half-sister's lover.

In a proceeding that took only 10 minutes, Christian Brando entered his guilty plea, which included a special allegation that he committed a crime with the use of a handgun, before a packed courtroom in Santa Monica, adjacent to Los Angeles.

Brando, dressed in a charcoal gray suit, white shirt and burgundy tie, was somber throughout. His only comments came in one-word sentences -- "Yes" and "Guilty" -- when asked if he waived his rights and how he pleaded.

Later, as his lawyer addressed a throng of reporters gathered outside the courthouse under drizzling gray skies, the 32-year-old free-lance welder slipped quietly away in a chauffeur-driven black Mercedes-Benz.

His father, who has been at his side through most of the court proceedings in the case, did not attend. "He was in no emotional position to come out today," defense lawyer Robert Shapiro said of the legendary actor. "His thoughts, his love and his feelings are with Christian."

The younger Brando now faces a maximum of 16 years in state prison in the May 16 death of 26-year-old Dag Drollet, the lover of Cheyenne Brando, 20. Los Angeles County Superior Court Judge Robert W. Thomas scheduled sentencing for Feb. 26. In the meantime, Brando remains free on bail.

Cheyenne, who had dinner with her half-brother on the night of the fatal shooting, was a crucial witness in the case because she was the only person who could testify about Christian's state of mind before the shooting.

But in June, shortly after telling authorities she believed the killing was a murder, Cheyenne left for Tahiti. She has since tried to commit suicide twice, and has been declared mentally incompetent by French authorities. Her lawyer said yesterday that she recently received permission to go to France for psychiatric treatment.

Prosecutors in Los Angeles spent six months trying unsuccessfully to compel her to return to testify. But judge after judge turned them down.

After a last-ditch meeting Thursday in which they tried to persuade Cheyenne's lawyers to have her come back voluntarily, the prosecutors gave up. They then called Brando's lawyer, Shapiro, who had said months ago that he felt a guilty plea to manslaughter would be appropriate for his client.

The chief prosecutor, Deputy District Attorney Steven Barshop, said that he was "personally disappointed" at the outcome. But, he acknowledged, without Cheyenne Brando he did not have a murder case.

"Without her, we cannot legally prove malice and without being able to prove malice, this case is a provable manslaughter," Barshop said. "With her, this case is a murder -- at least, a tryable murder."

Barshop said that he will request the maximum 16-year prison term for Christian Brando. "He is not walking away from this case," the prosecutor declared.

Shapiro, however, maintains the killing was an accident. He called the plea bargain "fair, just and equitable," saying: "This is a case, when all the facts are known, that will cry out for leniency."

The defense lawyer also said that he believed Cheyenne Brando would not have made a credible witness -- a point prosecutor Barshop disputed. The guilty plea, which came 10 days before the trial was to begin, may be more of a beginning than an end to the Christian Brando drama. The younger Brando must now face a lengthy sentencing hearing, which lawyers estimate could last as long as three days.

The hearing, a mini-trial of sorts, will include a parade of witnesses. Moreover, prosecutors say that they expect to introduce evidence that would likely have been inadmissible at trial, including statements by Cheyenne, a statement by Christian Brando that was taken in violation of his Miranda rights and evidence that he had been violent with his former wife.

Marlon Brando, who was home when the fatal shooting occurred at his hilltop Los Angeles estate, is among those expected to testify at the sentencing, as is Drollet's father, Jacques.