LOS ANGELES, JAN. 28 -- The murder trial of Lyle Menendez ended today in a mistrial, but the saga of the Beverly Hills brothers who killed their wealthy parents is headed for a courtroom reenactment.

Prosecutors today vowed to retry Lyle and Erik Menendez on first-degree murder charges, a threat made weeks ago while separate juries were still working to decide why Lyle or Erik Menendez ambushed their parents in their family mansion.

The trial, which riveted cable television audiences for months, ended shortly after noon, after Lyle's jury told Superior Court Judge Stanley Weisberg for the third time that it could not reach a unanimous verdict.

The juries heard testimony about each man and deliberated separately. Erik's jury ended in deadlock two weeks ago. A hearing will be held Feb. 28 to set a new trial date.

The juries' failures were widely deemed as victories for defense attorneys Jill Lansing and Leslie Abramson, who portrayed Lyle, 26, and Erik, 23, as abused sons who killed out of fear.

Abramson, who defended Erik vigorously in court as well as during informal sidewalk interviews, said today that double deadlocks in the six-month trial showed that "a large number of jurors accepted the truth."

Abramson, who made the statement during a press conference on live television, used the opportunity to show off some of the savvy that made her formidable in the courtroom: She quickly asked viewers to send donations for Erik's retrial and reeled off an address where money can be sent.

District Attorney Gil Garcetti said in a press conference this afternoon that the brothers' defense "boggles my imagination" and that he would pursue the brothers, and a death penalty for each, no matter what the cost.

"What is the message that we are trying to send as a society to everyone in this country? We have an ethical, professional and moral responsibility to go forward with this case as a first-degree murder case," Garcetti said.

"We're seeking justice," he said emotionally. "... And be damned with how much money it's going to cost." This six-month trial cost the state close to $1 million; the Menendez estate, once estimated at $14 million, has been largely exhausted, according to the brothers' attorneys.

Although Abramson has repeatedly said she and Lansing were willing to bargain with Garcetti and have the Menendez brothers plead guilty to lesser charges -- but not including second-degree murder -- Garcetti rebuffed her today. He maintained the prosecution claim that the boys were "living a Beverly Hills life" and acted out of greed to protect it.

"There will be no plea bargain in this case," he said.

Both Menendez brothers told the juries they shot their parents, Jose and Kitty Menendez, on Aug. 20, 1989, and admitted they lied about it for months. During the trial, each said they killed after years of mental and sexual abuse and after a confrontation with their parents.

Both brothers testified tearfully that Jose Menendez, an entertainment executive, had forced sexual relations on them; Kitty Menendez was described as sexually suggestive, sometimes dressing in front of Lyle and allowing him to touch her. The defense, however, said she knew about Jose's sexual abuse of the boys and did nothing to stop it.

After today's mistrial, the judge released tallies of each jury's voting. The results suggest prosecutors face a daunting challenge.

Three jurors on Lyle's panel voted to convict on first-degree murder of his father and his mother. Five jurors on Erik's panel also voted twice to convict on first-degree murder.

In each case, the jurors split deeply, with no more than six jurors agreeing on any possible conviction.

Court observers said the wide divergence in jurors' votes was just another surprise in a trial that regularly surprised, and sometimes shocked, those who followed the exhaustive examination of the Menendez family.

"In essence the juries split just like the viewers of Court TV," said Peter Arenella, a UCLA professor of criminal law, referring to the network that broadcast thousands of hours of the trial.

In addition to the three jurors who voted to convict Lyle of first-degree murder for killing his father, three jurors opted for the lesser crime of second-degree murder and six deemed him guilty of voluntary manslaughter.

Lyle's jury also could not agree on how culpable he was in the murder of his mother, despite the fact that he testified that he reloaded his shotgun, followed her as she tried to crawl away and then shot her at close range.

Three jurors voted for a first-degree murder conviction in her death; three for second-degree murder, five for voluntary manslaughter and one for involuntary manslaughter.

Erik's jury, which indicated its voting pattern didn't change from its first day of deliberations, appeared to take a tougher attitude toward the younger brother, who had been portrayed as the more vulnerable of the two. According to testimony, Erik was molested by his father for 12 years.

Beyond the five jurors who voted to convict Erik of first-degree murder for the killing of his father, one juror would have convicted him of second-degree murder and six others voted for voluntary manslaughter. In the death of his mother, five voted for a first-degree murder conviction, three for second-degree murder and four for voluntary manslaughter.

Six jurors on each jury voted to find the men not guilty of a charge of conspiracy to murder their parents.