By Phoenix Tso

LOS ANGELES (Reuters) - An old friend of Robert Durst, a real estate icon tied to slayings explored in HBO's series "The Jinx," acknowledged on the witness stand on Friday in Los Angeles that he has been inconsistent in describing what he called Durst's private confession to murder.

Nick Chavin, 72, a New York advertising executive who was a longtime friend of Durst, returned to the witness stand a day after testifying Durst told him that he killed mutual friend Susan Berman in 2000.

Prosecutors have asserted Durst killed Berman because of what she knew about his wife's unsolved disappearance in 1982.

Chavin testified on Thursday that in late 2014, outside a New York restaurant, Durst said he killed Berman. "I had to. It was her or me. I had no choice," Durst said, according to Chavin.

An attorney for Durst in cross-examination on Friday suggested Chavin had earlier described the conversation differently.

The attorney presented a transcript of Chavin's interview by Los Angeles prosecutors in April 2015, less than a month after Durst was charged with first-degree murder for Berman's 2000 execution-style shooting in Los Angeles.

In that earlier interview, Chavin said Durst had "mumbled something" outside the restaurant and that he "couldn't put together what that was."

Chavin acknowledged on Friday he had not wanted to be transparent with authorities at the time.

"What I should've said is I didn't want to tell you (prosecutors) about it," Chavin testified.

Chavin said Thursday that Berman had confided to him decades before that Durst admitted to her that he killed his wife, Kathleen Durst, when the couple lived in New York.

Durst, 73, has pleaded not guilty to first-degree murder in Berman's death. He also has denied having anything to do with the disappearance of his wife, whose body was never found. He was not charged in that probe.

Durst's ties to both cases, and his 2003 acquittal in the killing and dismemberment of a Texas neighbor, were chronicled last year on HBO in its popular documentary series "The Jinx."

Durst was formally charged with killing Berman a day after HBO aired the final episode, in which Durst was recorded muttering to himself off-camera: "What the hell did I do? Killed them all, of course."

Berman, 55, was found shot to death in her home a couple of months after it was revealed police in New York had reopened an investigation into the disappearance and presumed slaying of Kathleen Durst.

The judge, in a rare arrangement, allowed Chavin and another witness to take the witness stand early in the case, with their testimony videotaped and preserved in the event they die or become incapacitated before Durst's trial, which is not expected to begin before next year.

(Writing by Alex Dobuzinskis; Editing by Alistair Bell and Jonathan Oatis)