Family of Susan Berman Pleads with Robert Durst to Tell First Wife's Family Where Body Is

Robert Durst, 78, was sentenced to life in prison without the possibility of parole on Thursday

Family of Susan Berman Pleads with Robert Durst to Tell First Wife's Family Where Body Is

Sareb Kaufman, the stepson of Susan Berman, had a request for Robert Durst at the real estate scion sentencing on Thursday for murdering his stepmother: Kaufman believes Durst also killed his first wife, Kathie, and buried her body. He pleaded with Durst to tell Kathie's family where she is.

"I hope in your final days and hours, you will come to the same understanding and give [Kathie Durst's family] what little they are asking for, to find Kathie, to lay her to rest appropriately, finally, at long last," Kaufman said during sentencing Thursday. "This is the most important question that still haunts us."

Last month, Durst, 78, was convicted of Berman's 2000 execution-style murder. Prosecutors said Durst killed Berman because she knew too much about the 1982 disappearance of Kathie Durst, a 29-year-old medical student at Albert Einstein College of Medicine, and that Durst feared she would go to the police. Prosecutor's also called many witnesses who testified about Durst's alleged abusive relationship with his first wife.

Kathie was last seen alive on January 31, 1982, when she appeared at a friend's dinner party, looking upset. Durst later filed a missing persons report, telling police they'd had a fight later that night at their South Salem, N.Y., cottage and that he'd driven her to the station to catch a train to New York City. She was never seen again. Prosecutors in Los Angeles and police in New York believe Durst killed her.

"Perhaps you can find some small redemption in an act of humanity," Kaufman told Durst at the sentencing. "You have murdered the only people who you were ever able to inspire to love you. You took them for granted and abused their love. ... Any hope of any kind of redemption you can find is letting them know where to find Kathie."

An attorney for the siblings said they were upset that they weren't allowed to confront the man they believe killer their sister 40 years ago.

"The whole case was about Kathie and it is pretty disgusting that they don't get a chance to confront Durst," attorney Robert Abrams tells PEOPLE. "By coming to Los Angeles to see Durst get sentenced after sitting in the gallery it would be part of a Hollywood spectacle that demeaned their loss. They have every right to confront Durst."

According to Dave Ring, a Los Angeles-based victims' rights attorney, California law does not allow them to do so, Ring told the Los Angeles Times.

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"There is absolutely no justice for Kathie's family," says Abrams. "He has never been charged or convicted for the murder or disposal of her body. Until he is held accountable in New York this case will continue."