LOS ANGELES (Reuters) - Real estate scion Robert Durst and his wife were unfaithful to each other before she went missing in 1982, a friend of Durst said in court on Tuesday, in testimony that could be used by prosecutors to show there was discord in the marriage.

FILE PHOTO: Real estate heir Robert Durst appears in a criminal courtroom in New York, U.S. on December 10, 2014. REUTERS/Mike Segar/File Photo

Los Angeles County prosecutors have accused Durst of first-degree murder, saying he shot to death his friend Susan Berman, 55, in 2000 because of what she knew about the unsolved disappearance and presumed slaying of his wife, Kathleen.

Emily Altman, who has been friends with Durst for 45 years and whose husband, a lawyer in Mineola, New York state, has done legal work for the multimillionaire, was called to testify in Los Angeles Superior Court by prosecutors who asked her about Robert and Kathleen Durst’s relationship.

Robert Durst’s ties to three mysterious deaths were explored in HBO series “The Jinx” in which he admitted that he had on occasion struck his wife.

Altman said Kathleen, who also went by Kathie, was gaining independence from Durst before she went missing, attending medical school in New York City and pursuing a career.

“Kathie was seeing other people, Bob was seeing other people, they both were seeing other people so it’s not like one person was completely honest in the relationship and one wasn’t,” Altman testified.

At another point in her testimony, a prosecutor asked Altman if she had known Durst to lie when it was “to his advantage” and she responded, “Yes.”

Altman said she learned Kathleen Durst had gone missing when Robert told her by phone soon after it happened.

“I remember he was really upset,” she said.

Durst, 74, has denied having anything to do with the disappearance of his wife, whose body was never found. He was never charged in her death.

“The Jinx” chronicled Durst’s ties to his wife’s disappearance, Berman’s slaying and Durst’s 2003 acquittal in the killing and dismemberment of a Texas neighbor.

Prosecutors in 2015 formally charged Durst with killing Berman, who was a writer, a day after HBO aired the finale of the documentary mini-series. In that, Durst was recorded muttering to himself off-camera, “What the hell did I do? Killed them all, of course.”

Durst’s trial is not expected to begin before next year but the judge is allowing some witnesses to testify early, preserving their statements in case they die before the trial.