. >> reporter: laura nirider of northwestern university's innocence projececis a leading expert in false confessions by young people.. she rereesents brendan dassey of "making a murderer" fame. nirider heard about robert's case and offered to help. and help us understand what happened to robert, as we watch the interrogation unfold. >> this is one of the most intense interrogations that i've ever seen. >> you have the right to remain silent. anything you say can and will be used against you in the court of law. >> you've got these officers -- very, very close to robert who's a big guy pushed into that corner, increasing the pressure without even touching him. >> reporter: randy snead -- a begins the interview at 2:00 am, by which time rorort has been awake 18 hours. >> never been in that house? no. >> repororr: again and again, more than 70 times. >> start telling the truth. >> i am. >> reporter: robert insists he is innocent. >> i had nothing to do with this. i swear to god. asks for a polygraph. >> i will take a polygrara test right now. i am being honest. i will take a polygraph test.

. >> reporter: which, said laura nirider, is about the least robert deserves. robert, and untold others now languishing in american prisons, who confessed under duress to something they didn't do. >> slowly, these stories are >> he lives here, but i haven't run into him. and if i was to see him walkin' down the street, i'd probably just keep walkin', 'cause i don't really have nothin' to say so. i told you that i was innocent." >> reporter: so he was. so he is. >>> that's all for this edition of "dateline." we'll see you again friday at 10:00, 9:00 central and of course i'll see you each week night for "nbc nightly news." i'm lester holt. for all of us at nbc news, good night. ght. [ sweeping orchestral music