Durst, who was profiled in the HBO documentary "The Jinx," is on trial for the killing of his friend, writer Sharon Berman. Prosecutors said Berman knew too much about the death of Durst's first wife Kathleen.
Durst's former friend Peter Schwartz testified that he saw a violent side of Durst firsthand in January 1981.
He said while they were at an apartment, Durst attacked him without provocation while he was talking to Kathie Durst.
Friend testifies millionaire Robert Durst said he killed his wife
Schwartz said Durst, wearing pointy boots, kicked him between his legs and under his eye, then shoved him into a radiator, injuring his back and fracturing his face.
Schwartz showed photos of his injuries from the time in the courtroom.
Schwartz said it happened at Durst's apartment in New York after a party, with Durst's wife Kathie nearby.
Schwartz alleged the unprovoked attack happened after Durst left the party with a group of people, and later returned agitated and enraged.
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Criminal charges were filed against Durst for which he entered a plea in exchange for the incident being expunged from his record, pending his staying out of trouble. Schwartz later settled a civil lawsuit against Durst.
Prosecutors are trying to prove Durst had a history of violent behavior.
Durst has denied all the charges.
The trial itself is not expected to get underway until 2018. Schwartz is one of several witnesses being called to testify in early hearings. Some are being called early because of their age and some because of fears that Durst would try to pay to injure them before they could testify.
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