Los Angeles (AFP) - US real estate scion Robert Durst was sentenced Thursday to life in prison with no possibility of parole for the killing of his best friend.

Durst, a multi-millionaire who was the subject of an explosive HBO documentary entitled "The Jinx," has always denied charges that he shot that friend, Susan Berman, in the back of the head in 2000 at her Beverly Hills home to keep her from talking to police about the disappearance of his wife two decades earlier.

But last month, a jury in Los Angeles took just eight hours to find the 78-year-old guilty of the execution-style slaying of Berman.

"This crime was a witness killing," Judge Mark Windham said before reading out the life sentence. "That circumstance... tremendously aggravated this awful, disturbing crime."

Windham rejected the defense's request for a new trial, saying, "There is sufficient, in fact, overwhelming evidence of guilt."

The court also heard from Sareb Kaufman, a son of Berman who said he has wondered what his life would have been like had Durst not killed his mother.

"Every plan was completely swept away," a crying Kaufman said. "You also murdered me, the person I was."

Durst sat motionless in a wheelchair during Thursday's court session.

Prosecutors say he murdered crime writer Berman to prevent her from being questioned by New York police over the disappearance of his wife Kathleen.

Berman, the daughter of a Las Vegas mobster, had acted as a spokeswoman for Durst after he became a suspect in the wife's disappearance.

'Killed them all'

Durst, an estranged member of one of New York's wealthiest and most powerful real estate dynasties, was never charged in his wife's case.

He was arrested in March 2015 in a New Orleans hotel room in connection with Berman's murder, hours before the final episode aired in the HBO documentary "The Jinx: The Life and Deaths of Robert Durst."

In its stunning finale, Durst is heard muttering to himself, "There it is, you're caught" and "Killed them all, of course" -- apparently unaware that a microphone he was wearing during the recording of that episode remained switched on while he used the restroom during a break in the session.

In Thursday's proceedings, Berman's relatives urged him to say where his wife's body is.

The docuseries also delved into the 2001 death of Durst's neighbor in Texas, Morris Black, who was found dismembered. 

Durst admitted to the dismemberment but claimed the killing was self-defense. He was acquitted.

He repeatedly denied any involvement in Berman's death, but acknowledged he had written an anonymous letter to police telling them that her body lay in her Beverly Hills home.

Last month, prosecutor John Lewin told the jury there was a "mountain of evidence" that Durst had killed all three people with whose deaths he had been connected.

He said a friend of Durst had testified that the real estate magnate had told him of Berman, "It was her or me. I had no choice."

"He has never been held accountable for his domestic abuse of (wife) Kathie. He was never held accountable for her death. The last 20 years, he's gotten away with murdering Susan," Lewin told the jury. 

"For the last 20 years, he's avoided responsibility for Morris Black. Durst is not jinxed. He's a three-time killer who has managed to escape accountability until this very moment."