LOS ANGELES, JUNE 24 -- O.J. Simpson's defense attorneys today won a key tactical victory when a judge aborted the grand jury investigation of the murder of his ex-wife and her male friend because it may have been influenced by the storm of publicity surrounding the case.

The unusual ruling by Superior Court Judge Cecil J. Mills forces the prosecution to disclose much of the evidence against Simpson at a preliminary hearing set for next Thursday and gives defense attorney Robert L. Shapiro the opportunity to try to challenge prosecution witnesses.

It also underscores the extraordinary amount of media coverage the Simpson case has received and the impact it is likely to have in the months ahead.

If it is hard to empanel a grand jury unaffected by coverage less than two weeks after the murders, defense lawyers said today, it may be even more difficult to find an untainted jury to try the case.

It was the latest astonishing development in the case against the 46-year-old former football superstar, whose defense team today grew by two of the nation's most famous attorneys -- F. Lee Bailey and Alan M. Dershowitz. Simpson, who has pleaded not guilty to a charge of double murder, had been brought from his jail cell for the hearing and appeared to smile when Mills made his announcement.

Mills did not specify what information may have reached the grand jury, saying only that "as an unanticipated result of the unique circumstances of this matter . . . some jurors have become aware of potentially prejudicial matters not officially presented to them by the district attorney."

Lawyers said the ruling was at least a temporary blow to prosecutors. But at a news conference this afternoon, Los Angeles County District Attorney Gil Garcetti insisted that he had initiated the request as a result of the publicity given a 911 call recorded last year in which an enraged man identified as Simpson is heard threatening his former wife, Nicole Brown Simpson after breaking down a door. The incident occurred almost eight months before Nicole Simpson, who was 35, and Ronald L. Goldman, 25, were slain.

"I did this because I am interested in justice," said Garcetti, whose office has been under fire for its handling of a series of highly publicized cases in recent months. He added that he was concerned that any indictment would be tainted if it were later revealed that a member of the grand jury had heard evidence "outside the grand jury process."

Garcetti strongly criticized the release of the 911 tape Wednesday by Los Angeles police in response to requests by the news media. The tapes and other police records released with it provided stark details of the troubled relationship between the Simpsons, and reveal a violent side of O.J. Simpson that sharply contrasts with his public image.

Shapiro contended today the tape is inadmissible in the murder proceedings against Simpson -- a position legal experts say is open to question -- and he blamed Garcetti for the tape being made public and for other statements that he said were inappropriate.

"The District Attorney's Office has improperly released -- and massive publicity has been given by the media to -- inadmissible evidence in this case, the best example of which was the massive airing on virtually all television and radio stations in Los Angeles of the 911 tape," Shapiro said.

Shapiro also criticized public remarks by Garcetti and members of the prosecution team. He said it was "unconscionable" for them to make any statements about the case before Simpson was arraigned and argued it "can reasonably be expected" that the 23 members of the grand jury had been exposed those news reports.

Shapiro requested that each member of the grand jury be interviewed to see if the news coverage had affected their deliberations. But at his news conference, Garcetti insisted that he was the one who had initiated the meeting with Mills, the Superior Court's presiding judge, to voice his concerns about the coverage's impact.

Peter Arenella, a UCLA law professor, described Mills's decision as "extraordinarily unusual." He and other legal experts said the ruling was a clear victory for Shapiro but not necessarily an insurmountable setback for Garcetti.

Prosecutors usually have a choice of using either a grand jury indictment or a preliminary hearing in bringing a suspect to trial. By law, however, a defendant is entitled to a hearing within 10 days of arrest, and if no indictment is obtained in that period the hearing automatically takes place. In Simpson's case, that deadline is next Thursday.

At a preliminary hearing, prosecutors present their evidence before a magistrate in what is in effect a mini-trial. If the magistrate makes a probable cause finding, Simpson will be bound over for trial.

At the hearing, Shapiro will be able to cross-examine any witnesses that prosecutors present and will be better able to gauge the kind of case prosecutors expect to present. By contrast, defense attorneys do not participate in grand jury hearings and must rely on a transcript to know what happened.

With a grand jury, Shapiro "would in effect be putting a glass to the wall," said Robert Pugsley, a professor at Southwestern University School of Law. With a preliminary hearing, by contrast, "he's going to be a major player."

Garcetti denied the ruling would hurt the prosecution's case. "Setback? No, not all all," he said. "The main reason to go to the grand jury is because of speed. It {the case} gets to the Superior Court quickly. Now we're set for the preliminary hearing on Thursday. We're ready to proceed. We will proceed."

Arenella suggested that the preliminary hearing could in fact help the prosecution in its effort to sway public opinion in a case involving a celebrity as popular as Simpson.

"If he {Garcetti} has some very powerful evidence of guilt, presenting it in a public forum might be helpful to prosecutors," Arenella said.

Another example of the problem confronting prosecutors in building their case emerged today when James Epstein, attorney for Jill Shively, said his client had been eliminated as a witness by the prosecution because she had already sold her story -- for $5,000 -- to the tabloid television show, "Hard Copy." She had appeared twice before the grand jury this week.

Shively, 33, a neighbor of Nicole Simpson, was an unidentified witness on the show who said she saw O.J. Simpson racing away from the area of Nicole Simpson's house around the time of the murder. She said Simpson "looked crazy, he was enraged," and that he ran a red light and yelled at another motorist. "I thought he was drunk," she said.

Epstein said Shively had hired him Wednesday before her second grand jury appearance because, "The D.A. got so mad at her she got scared."

"She had gone on 'Hard Copy' and they were afraid that that will give the defense attorney ammunition to disregard her testimony," Epstein said. "In their eyes, she tainted her testimony."

"She was just naive and didn't know it would cause a problem," he said. "She was called back a second time because the D.A. wanted the grand jury to know that {the prosecution} didn't know she had already talked to 'Hard Copy' before she testified."

Both prosecutors and defense attorney have complained about inaccurate news reports evolving from the case. In a separate court hearing this morning, Deputy District Attorney Marcia Clark clarified the existence of a piece of evidence. She disclosed that a blue knit cap, found at the feet of one of the victims, is among the prosecution's evidence.

Earlier this week, Clark said in court that, despite news media reports, a bloody ski mask had not been recovered from Simpson's home.

Meanwhile, the Los Angeles Times reported that Simpson used a baseball bat to smash Nicole Simpson's windshield during a 1985 incident. According to the Times account, which cited unnamed law enforcement sources, police responded to the call and found an agitated Simpson who told them: "It's my car. I'll handle this. There is no problem here."

Simpson's attorney Shapiro declined to comment on the report. He had confirmed last week that Simpson had once struck his wife's car with an unidentified object.

Lt. John Dunkin, a Los Angeles police spokesman, would not confirm the report. He said police were obeying an information blackout agreed to yesterday after a closed-door meeting among Garcetti, Los Angeles Police Chief Willie L. Williams and City Attorney James Hahn.

Garcetti said he ordered the blackout to ensure that "information is not improperly released" so that O.J. Simpson could receive a fair trial. Police department officials said they had received "many calls" from people who complained that the information, which by state law is deemed a public document, was released before the trial.

The tapes and report were issued Wednesday to news agencies that had filed formal requests under California's Public Records Act.

Dunkin said a departmental ban on releasing information is not unusual in high-profile cases, citing a similar prohibition during the recent allegations of possible child molestation against pop star Michael Jackson. The state law allows for delays in cases where disclosure "might endanger a legitimate government interest" such as criminal prosecution, according to the city attorney's office.

Staff writers Christine Brennan in Los Angeles and Saundra Torry in Washington and special correspondent Kathryn Wexler in Los Angeles contributed to this report.