A key witness says 'Jinx' subject Robert Durst admitted he killed his wife to future victim

Robert Durst - the subject of HBO's popular documentary series "The Jinx" - admitted to killing his wife, Kathleen Durst, to his longtime friend Susan Berman, a key witness alleges.

Durst has been charged with murdering Berman in her Los Angeles home in 2000. Kathleen Durst disappeared in 1982, and her remains have never been found to this day.

In a pre-trial hearing in Los Angeles on Thursday, witness Nathan "Nick" Chavin, 72 - another close friend of Durst - said that Durst told Berman that he killed his wife.

According to the Los Angeles Times, Chavin recalls that Berman said, "Bob killed Kathie." When Chavin asked Berman how she knew, she reportedly said, "He told me. We have to do what we can to protect him."

Chavin was brought into court as a "secret witness," according to the LA Times, and was flanked by bodyguards.

Prosecutors allege that Durst killed Berman because she knew that he killed his wife, who has never been found. Durst denies murdering both women, though "The Jinx" famously ended with the explosive reveal of Durst saying, "I killed them all" into a mic while in a bathroom when he seemingly didn't think anyone was listening.

In 2003, Durst admitted to murdering and chopping up the body of his neighbor Morris Black, yet he was not convicted after claiming he did it out of self-defense.