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Multimillionaire Robert Durst is a "menace to society" and a danger to several witnesses in his murder case, prosecutors said in an effort to preserve their testimony in case they get killed.

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Durst has killed two people who had information in the mysterious disappearance of his first wife and was prepared to kill others who might have stopped him, Deputy District Attorney John Lewin said in court papers before a hearing Friday in Los Angeles Superior Court.

"Defendant is a menace to society," Lewin wrote. "He has demonstrated a willingness to use deadly force to escape justice — killing two people and arming himself with deadly weapons to kill anyone who stood in his way of escape."

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Defense lawyers have blasted the request, saying it's absurd that the frail 73-year-old who is behind bars is a threat to anyone. They also said it was premature, coming before the scheduling of a preliminary hearing to determine if Durst faces trial, as well as a violation of his right to a fair trial.

"There is simply no factual basis upon which one could claim that Mr. Durst has the ability to harm anyone," attorney Donald Re wrote in court documents.

The defense also is fighting the prosecutor's request to keep from disclosing the names of at least two "secret witnesses" until shortly before their testimony.

Prosecutors want to keep their identities under wraps for their safety. The testimony will be videotaped and used at a possible trial only if they can't appear in court.

Durst has pleaded not guilty to one count of first-degree murder in the fatal shooting of his best friend, Susan Berman, in 2000. Lewin said Durst killed her because she had incriminating information in Kathleen Durst's 1982 disappearance in New York.

Prosecutors are taking an aggressive approach in publicly laying out their theory on the case before knowing if it will go to trial and evidence they might present.

The defense has objected to some of the information prosecutors have revealed, including a transcript and recording of a nearly three-hour interrogation of Durst following his arrest in New Orleans in 2015.

One witness Lewin wants to question is a doctor who may have been the last person to speak with Kathleen Durst. No charges have ever been brought in the suspected killing of Durst's first wife, whose body has not been found.

He may also call witnesses to the killing of Durst's elderly neighbor in Galveston, Texas, in 2001. Durst was acquitted of murder after testifying that he shot Morris Black in self-defense and then chopped up the body and dumped it in the sea. He was convicted of tampering with evidence and jumping bail.

The prosecutor says Black was killed because he knew the identity of Durst, who had disguised himself in Texas as a mute woman.

Durst, an estranged member of a New York real estate empire, fled to Galveston after learning the investigation into his wife's disappearance had been reopened in fall 2000, Lewin said.

Berman, who had served as an unofficial spokeswoman for Durst, was killed weeks later in her Los Angeles home before she was supposed to speak with police about that investigation.

Lewin said that with Durst's estimated $100 million fortune, he poses a serious threat to witnesses.

"The idea that he does not have the wherewithal to intimidate, buy off or attempt to have witnesses killed who possess inculpatory evidence because he is 'old,' 'frail,' or in custody, is ludicrous," Lewin said.

Judge Mark Windham tentatively set a Feb. 14 hearing for two witnesses to be questioned if he OKs the prosecutor's request.