Lead Prosecutor Explains How Robert Durst Was Finally Convicted After Decades Of Evading Responsibility

The lead prosecutor who secured a murder conviction against multi-millionaire real estate heir Robert Durst is speaking out about how he did it.

Los Angeles Deputy District Attorney John Lewin is featured on a Friday episode of “20/20” entitled "The Devil You Know," in which he reflects on how he destroyed Durst’s credibility on the stand.

"We were trying to get the jury to understand that this is a guy who doesn't believe that any rules apply to himself. That's just Bob Durst,” Lewin says on the program, adding, “he's the most self-involved person I've ever seen." 

Lewin successfully got Durst convicted last September for the 2000 murder of his confidante Susan Berman. He was sentenced to life for the crime, which prosecutors said he committed after learning that prosecutors in New York wanted to reopen an investigation into his first wife Kathleen “Kathie” McCormack Durst’s 1982 disappearance and presumed murder. Investigators claim that Berman must have had information about it that Durst wanted ensure never came to light.

"So there's gonna be three killings that we are going to prove," said Lewin. "Everything starts with Kathie Durst's disappearance and death … and that after that he had to kill Susan Berman because he feared she was going to talk, and then he had to kill Morris Black because Morris Black knew who he was and was putting pressure on him."

Morris Black was a neighbor of Durst in Galveston, Texas in 2001. Durst had moved there after learning of the possible reopening of Kathie's case and posed as a deaf, mute woman. Black, prosecutors said, learned Durst's true identity and Durst fatally shot him soon afterward. While he admitted to killing Black and disposing of his dismembered remains in Galveston Bay, he was acquitted of that murder at a 2003 trial, arguing that he'd acted in self-defense.

"He can do whatever he wants, whenever he wants to do it, that's how he's lived his life," Lewin says on “20/20,” referring to Durst’s tendency to get away with consequences.

He said he wanted to show the jury what made Durst “tick.” In turn, he pushed him to admit to lying to police in the immediate aftermath of his wife’s vanishing as well as in regards to details about Berman’s murder.

Shortly after his conviction in Berman's death in California, Durst was indicted for Kathie's murder in New York's Westchester County, where the couple had lived. However, Durst died in custody at the age of 78 of natural causes. Because he started the appeal process for the California conviction, it has been automatically vacated following his death.

In January, Lewin told Oxygen.com by phone that even though that conviction has been vacated, “I don’t think there’s any human being who watched this trial who has any doubt that Bob Durst is responsible for the killing of three people.”