Robert Durst’s marathon testimony over three weeks — in which the ailing millionaire denied killing his wife and best friend but also said he’d lied if he had done so — concluded Wednesday and lawyers rested their cases in the murder trial.

The New York real estate heir tried to counter or explain incriminating evidence in three killings that have shadowed him for decades, but was crippled by a cross-examination that the judge said was “devastating” to Durst’s believability.

It will be up to jurors to weigh his fate. Closing arguments are scheduled Sept. 8 and deliberations are expected to begin a week later.

Durst, 78, has pleaded not guilty to murder in the point-blank shooting of his friend, Susan Berman, in her Los Angeles home in December 2000. On the witness stand, he repeatedly denied killing her and said he doesn’t know who did.

Prosecutors said he silenced Berman because she planned to tell New York authorities that she provided a false motive for Durst after his wife vanished in 1982. They were able to introduce evidence that he killed Kathie Durst, who has never been found, as well as evidence that he intentionally killed a Texas neighbor in 2001.

Durst was acquitted of murder in the death of Morris Black after testifying that the Galveston neighbor pulled a gun on him and was shot during a struggle for the weapon.

If Durst’s testimony in that case saved him, his decision to speak publicly about his life afterwards may have come back to haunt him.

Durst said he deeply regretted speaking with filmmakers for a documentary on his life that unearthed key evidence in the Berman killing and revealed an off-camera moment that many viewers interpreted as a confession. His performance in front of jurors has already earned a bad review from the judge in the case.

“On day one, it appeared that you really effectively destroyed any possible credibility of this witness,” Judge Mark Windham told the prosecutor last week after jurors were excused. “By day three, I think you had very, very serious — I would even say profound — admissions.”

The trial of Durst began in March last year but was abruptly halted after just a few days because of the coronavirus pandemic. The case resumed May 17 as Windham brought jurors back to court and joked, “Where did we leave off?”

At the time, lawyers for Durst who has myriad health problems, asked for a delay for medical treatment, suggesting he might not live through the trial.

Durst, who sat in a wheelchair, was often slumped at the defense counsel table.

Despite speaking in a hushed tone, he came alive on the witness stand with enough stamina to testify for hours day after day without appearing to fade.

Durst denied killing Berman or his wife, who has been legally declared dead. He’s never been charged with a crime related to her disappearance. He stuck to his story that Black was killed during the struggle for the gun.

Durst, who had long denied being in LA at the time of Berman’s death, testified that he found her dead in her home.

He admitted for the first time that he lied for decades about sending an anonymous note to police directing them to Berman’s lifeless body. He said he had feared he would be accused in the killing if he was known to have been in her home at the time.

He acknowledged that it seemed hard to believe the killer had not written the letter.

“I have difficulty believing it myself,” he testified. “It’s very difficult to believe, to accept, that I wrote the letter and did not kill Susan Berman.”

He explained that the seemingly damning climactic scene in “The Jinx: The Life and Deaths of Robert Durst” was not a confession.

After being caught by filmmakers in a lie about the cadaver letter, Durst went in a bathroom where he muttered to himself on a live microphone, “Killed them all of course.”

Durst said said he either spoke too softly or didn’t express what he was thinking: “They’ll all think I killed them all, of course.”

Deputy District Attorney John Lewin, who grilled Durst for two weeks, asserted outside the jury’s presence that he had never seen a defendant lie so many times.

Durst acknowledged that he’d lied under oath and would lie to get out of trouble.

“What I’m saying is mostly the truth,” Durst said. “There are certain things I would lie about, certain very important things.”

On Wednesday, Lewin’s final question of the trial returned to the issue of what Durst would be unwilling to divulge.

“You’ve repeatedly admitted that if you had killed either Kathie or Susan or both of them you would never tell us,” Lewin said. “Correct?”

“Correct,” Durst said.