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A brief phone call that happened 35 years ago took center stage Tuesday at a hearing in the Robert Durst murder case.

The call was thought to be the last time that anyone heard from Durst's wife Kathie before she vanished, although prosecutors are now raising the possibility that it wasn't her on the other end of the line.

Prosecutors allege that Durst, the millionaire real-estate scion and subject of the HBO series "The Jinx," killed Kathie and then nearly 20 years later murdered his friend Susan Berman because she knew too much about the slaying.

Durst, 73, is charged only with Berman's slaying — and prosecutors wanted to get testimony from three witnesses who they say are in fear of Durst.

The first was Dr. Albert Kuperman, a former dean of a New York medical school where Kathie Durst was a student at the time of her disappearance.

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He testified that a woman who identified herself as Kathleen Durst called him on Feb. 1, 1982, to say she was sick with "gastrointestinal distress" and would not be in.

The prosecution and the defense sparred over how to describe the caller.

Throughout his cross-examination, Durst lawyer Dick DeGuerin emphasized that it was Kathie Durst who called Kuperman, The doctor testified that for 30 years "he had no reason not to believe it was Kathie who called him" and that he had been told she would call him at some point to discuss her attendance.

But Kuperman later testified that after meeting with Deputy District Attorney John Lewin and investigators in 2015, he began thinking about the call more critically and wasn't absolutely certain it was Kathie on the phone that day.

Who made the call is significant because it could bolster or undermine Robert Durst's timeline for when and where he last saw his wife. In addition to establishing a timeline, prosecutors want to leave open the possibility that the call came from someone else impersonating her.

Throughout his cross exam, Durst lawyer Dick Dick DeGuerin said it was Kathie Durst who called Kuperman in 1982. Kuperman testified that for over 30 years "he had no reason not to believe it was Kathie who called him" and that in fact he had been told she would be calling him at some point.

But Kuperman did admit when questioned by Lewin that after meeting with prosecutors and investigators in 2015 he began thinking about it more critically and wasn't absolutely certain Kathie was the caller.

During the daylong hearing, the two sides also fought over how to refer to "The Jinx," with prosecutors calling it a documentary and DeGuerin saying it's just a "movie."

The show examined Durst's links to the 1982 disappearance of Kathie, the 2000 murder of Berman and the 2001 killing and dismemberment of Durst's Texas neighbor Morris Black. Durst was found not guilty in Black's death.

"The Jinx" ended with Durst's bombshell statement on a hot mic that he "killed them all."

One of the witnesses scheduled to testify at the three-day pretrial hearing has not yet been named. DeGuerin said there's some indication that witness is working on a book, "which would be rather sensational."