The dinner topic was an unpleasant one.

In 2014, Nick Chavin said, he was asked to dinner in New York City by his longtime friend Robert Durst to talk about two women who had disappeared from their lives: Durst’s first wife, Kathleen, and a writer they had both been close with, Susan Berman.

Durst, who had long been suspected in both his first wife’s disappearance and Berman’s slaying, had raised the topic before the two men connected that night, according to testimony delivered by Chavin on Thursday. But the topic remained unmentioned over the course of the meal.

It wasn’t until they stepped outside, Chavin testified, that he raised the issue.

“You wanted to talk about Susan?” Chavin asked. He said the question prompted a chilling reply.

“I had to. It was her or me,” Durst said, according to Chavin. “I had no choice.”

Chavin said he took the remark as a confession to Berman’s execution-style slaying. Chavin, a 72-year-old advertising executive who said he was a longtime friend of both Durst and Berman, testified at length in Los Angeles Airport Court on Thursday in the murder case against Durst.

“This is not easy,” Chavin said, his eyes welling up with tears on the witness stand.

Durst is unlikely to face trial until next year at the earliest, but prosecutors had asked to depose Chavin, whose identity had been shielded for months, because they feared he might be killed or could otherwise die before he got the chance to speak in front of a jury. Chavin was hustled into court earlier in the week as a “secret witness,” flanked by bodyguards who have kept an eye on him from the courtroom’s jury box.

Chavin will face cross-examination Friday by Durst’s legal team, spearheaded by Texas attorney Dick DeGuerin.

Durst, 73, was arrested in New Orleans in 2015 and charged with killing Berman, an author and longtime confidant of the real estate scion. Prosecutors allege Durst shot Berman in the back of her head inside her Benedict Canyon home in 2000 because he believed she planned to speak to investigators about his first wife’s 1982 disappearance.

Berman, a Las Vegas-born writer whose father was a mob boss, had acted as an informal spokeswoman for Durst, fielding constant media inquiries that followed Kathleen’s disappearance.

In addition to his testimony regarding Berman’s killing, Chavin said Durst had admitted to killing Kathleen in a conversation with Berman. Berman later relayed that information to Chavin, he said.

“Susan said to me, ‘Bob killed Kathie,’ ” Chavin testified.

Asked why he hadn’t told police of the admission earlier, Chavin said Thursday that Berman had insisted they protect Durst.

“Kathie’s dead, we can’t do anything about it,” Chavin testified Berman told him. “We have to protect Bob.”

Chavin told the court that Durst was best man at his wedding, and that the two had known each other for more than three decades. Durst drastically changed the trajectory of Chavin’s career by asking him to do advertising for some of the Durst Organization’s holdings, he said. The family-run company is a dominant player in the prime Manhattan real estate market. Durst’s father, Seymour, became one of Chavin’s mentors.

Despite their long-standing bond, Chavin delivered a series of punishing remarks in court. Aside from suggesting Durst had confessed to two separate slayings, Chavin said Kathleen Durst had admitted she was afraid of her husband, even fearing he might physically harm her.

Still, even after Berman told him of Durst’s supposed confession, Chavin said he did not believe his friend could have killed his wife. When he told a New York State Police investigator of Berman’s comments in 2001, Chavin said he believed Kathleen had been killed by a drug dealer.

He said his view changed later when Durst admitted that he had cut up the body of a neighbor in Galveston, Texas, and thrown the pieces into the local bay. Durst’s admission struck Chavin as disturbing. Until that point, Chavin testified, he had never believed Durst was “capable of hands-on violence.”

Durst was acquitted of murder in the Galveston case after arguing that his neighbor had been killed as the two men struggled over a gun that went off.

Edward J. Imwinkelried, a professor emeritus at UC Davis who coauthored the annotated California Evidence Code, said Durst’s attorneys would have a difficult time trying to prevent jurors from hearing Chavin’s testimony about Durst’s confession to killing Berman.

“Since [Durst] evidently makes this statement to a private party, who I assume at that point isn’t acting as an agent of the government, you don’t have any due process problems,” Imwinkelried said.

It is less likely that a jury would hear Chavin’s testimony about Durst’s supposed confession to killing his first wife, Imwinkelried said. Because Chavin said that he didn’t hear the confession himself but heard about it from Berman, a judge would consider it “double hearsay” and might not allow the testimony at a trial, the professor said.

“Judges are understandably, and quite justifiably, concerned about only admitting reliable testimony. When you’ve got double hearsay, you’ve got double the problem,” Imwinkelried said.

Chavin seemed to have struggled with the issue of testifying for some time. Prosecutors played a recording Thursday of an interview he gave prosecutors in April 2015. Chavin admitted Thursday that he had downplayed Berman’s comments during that interview out of loyalty to Durst.

“Susan exaggerated a bit,” he told prosecutors at the time, “and was somewhat of a liar.”

Later in the recorded conversation, prosecutors asked him if he thought Durst killed his first wife. Chavin said he did, but added that he believed his longtime friend had acted out of passion, not malice. At one point, he declined to say whether he thought Durst had killed Berman.

Even in court Thursday, Chavin appeared torn over the issue of speaking out against Durst.

“As you sit here, do you still feel a bond — and a warmth — toward Bob Durst?” a prosecutor asked.

“It sounds ridiculous, but yes,” he said. “This is a best friend who admitted to killing my other best friend.”

marisa.gerber@latimes.com

james.queally@latimes.com