john lewin: no, he did not. cus did show up for trial, but he was, to say the least, a reluctant witness: marcus singleton: in the beginning, when i first came to speak to mr. lewin, i had defended andre on my family's side. and i didn't wanna believe that he did it... then i found out that i'm probably gonna have to accept the truth. a truth that i don't really wanna have to accept even today, to be honest. josh mankiewicz: marcus told the jury his harrowing story of the fight he'd witnessed between his mom and his stepdad six weeks before her murder. marcus singleton: they were frantic and my mom was-- like, she was distraught-- i guess is the best word. like, she was just, like-- she was screaming. you know, she was, "call the police. call the police." josh mankiewicz: compelling... damning. but it turned out... the defense had a star witness too. josh mankiewicz: did you think andre was gonna take the stand? john lewin: no, i was-- i-- i was very surprised-- i would say shocked... josh mankiewicz: andre's def

it resumed 14 months later with deguerin continuing his battle against a tough deputy da named john lewin questioning by lewin, made this stunning admission. did you kill susan berman is strictly a hypothetical. i did not kill susan berman, but if i had, i would lie about it. keith morrison: in september 2021, a jury found robert durst guilty of first degree murder. he was sentenced to life without parole. two months later, a grand jury in new york indicted him for the death of his first wife, kathleen durst, but a jury would never hear that case. in january 2022, robert durst died in a california hospital while serving his life sentence. he was 78. and in a final twist, john lewin, the prosecutor in the berman case, said that because durst was appealing that verdict at the time of his death, under california law, his conviction will be vacated. robert durst may be gone, but the mysteries remain. andrea canning: coming up, a missing teenager. investigators wonder, is there a link? andrew mills: robert durst is a person of interest in this case. andrea canning: when "dateline" continues. t