The family of Robert Durst's first wife, Kathleen Durst, a former New Hyde Park resident who mysteriously disappeared in 1982, filed a wrongful-death civil suit Thursday against the real estate heir they believe killed her.

Durst, 72, is in federal prison in Louisiana on gun and drug charges and awaits trial in Los Angeles in the 2000 Beverly Hills killing of his close friend, writer Susan Berman. He has not been charged in the disappearance of Kathleen Durst, who was 29 at the time. He appeared to have confessed to her slaying in the HBO documentary series "The Jinx."

In the March 15 final episode of "The Jinx," Durst is caught in a moment in a bathroom when he apparently did not realize his microphone was still on mumbling that he "killed them all, of course" -- a statement authorities suspect was a reference to the deaths of Kathleen and others.

Durst previously told authorities he and Kathleen, a fourth-year medical student at Albert Einstein College of Medicine in the Bronx who was known as "Kathie," fought at their home in the Westchester County village of South Salem on the night of her disappearance on Jan. 31. But he said later she got on a train alone to New York City and he did not see her after that. Her body has never been found.

The couple met at a party in New York City and married in April 1973.

Kathleen's 70-year-old brother, Jim McCormack of Sparta, New Jersey, said Thursday night in an interview that his family has retained attorney Alex Spiro, a former Manhattan prosecutor, to handle the lawsuit, filed in Surrogate's Court.

"Everyone took his word for it," he said of Durst's account of what happened when McCormack's sister went missing. "We're filing a petition to finally get justice on behalf of Kathie and our family," McCormack said. "Until now [after 'The Jinx' airing], I had hope that she was somewhere out there. I've finally accepted the reality that she's dead."

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In a telephone interview Thursday, Spiro said, "He did it and we can prove it."

Durst was acquitted in 2003 in the killing two years earlier of his 71-year-old neighbor, Morris Black, whom he admitted to accidentally shooting in a struggle and then dismembering in a panic before dumping the remains in Texas' Galveston Bay.

McCormack's 101-year-old mother Ann still lives in the New Hyde Park family home. The family purchased the home in 1962 and Durst visited there several times for family gatherings.