College student found shot to death in Brooklyn after night of partying

Mark Fisher, a student at Fairfield University, was found dead on Oct. 12, 2003. He had been viciously beaten and shot five times.
9:33 | 04/07/18

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Transcript for College student found shot to death in Brooklyn after night of partying
Ood morning. He Are you ready? Here I am. E we . Rikers here we come. Doreen Quinn Giuliano has become far too Familia with rikers island, one O the coies most dangerous and notorious jails. Her son John jukea has bn behis since 2005, convicted of mdering a college phomore. John doesn't belong T. Whereoes he belong? Home. Reporter: It was known the New York tab lids as the grid kid murder, short for grid iron. But dor was convinced her was innocent. Does Ver cross your mind that maybe John did have thing to do with this? No. I'm a hundred percent sur did not. How can you be sure? The facts.just follow facts. Reporter: These facts, Doreen said, led her to take matters into her O hands. Going under cover and drtically changing her appearance, all to try to clear her son's name. There's a part of me that's symptic to her. And I almost admire that she not victim in this case. 'S mark fisher. Reporteolumbus day weekend 2003. Mark fisher heads to the big apple to explore the city's hopping bar scene. Mark fisher was every parent's dream, a big, strag, good looking student athlete, the prom king his high school. Phenomenal football player. Repore meets up with a group of guys that night, includingommy silay. A bunch of us went to bars on the St side. Bunch of guys? Bunch O guys. Cruising for chicks? R -- yeah. Cruising for chicks along with him thatt, his Wiman, June kea. Best friends? Yeah. Hang out every day, weekend. Reporter:fter some failed to score drinks with their fake I.D.S, 20-year- jukea invites everyone back to his house in Brooklyn, where mark fisher has no idea what he's about to get himself into. Why was deced to go to johnjukea's house? H mom was away and he a big house. It was an easy choice. So it was a little bit like, the CAS away, the mice will play. I was in Florida O a weekend vacation wit my husband. And John decided hrown impromptarty. There was a fs that got stranded in Manhattan and had no place to go. And THA party turned intoerhaps one O thegest mistakes of his life? Oh, yeah,absolutely. Rorter: Doreen says one of those mistakes, her son's decision to invite neighborhood D apple Antonio Russo, known for his dread locks, picking fi, and dealing marijuana. He was a bit of a wild card. Reporter: Some S jukea got ones bad side, mooing on the beer and weed. Fisher stumbles out the door, UND dead two blocks away on Argyle road. They found a male white, obviously theictim of several gun shots. Trauma to face. Reporter: Thetrapping football player from new jer is found shot five times in the back, laying on a blanket from jukea's home. It's a tab lidding frenzy over the grid kid slayi Antonio rus aracts cops' attention immediately. John jukea isut on trial for theder ofk fisher, a with pot pusher Antonio Russo, who cut off his dread locks the same D her is found dead. He had dread locks that he had cultivated for years. So for him T get them sheered was very suspect. Then he takes for California couple days ler. Reporter: Jukea also becomes a suspectecause T party was at his house. But the investigation slls out for days, weeks, and then months. That's whn aggressive prosecutor gets assigned to the ca. John jukea and Antonio Russo are charged wh murder. At trial, the star witness, a jailhouse snitch who had approached prosecutors with a story to tell. He's the last witness. According to him, John jukea elaborates on how he killed mark fier. Reporter: He testifies THA prison mate told Hime pistol-whipped mark fisher a then his buddy, Antonio ruo, shot him dead. Thi was an extreme atic moment at the trial. Nobody saw it coming. Reporr: Both are found guilty ofmurder sentenced to years to life. What wa your Rion to the fact that the jury came back with a verdict in twohours? Something was won Reporter: Outragy her son's guiltrdict, Jo mother decides to take action. Immey focusin on the jurors who so quickly convi her son. She W crazed with hifterria and terrified for her N's Fu. Orter: Fair to say what she ds next few mothers would ever consider. What made yecide to go under cover? When I mutual friend of John os was in the Audi, reized one of the jurors. The guy with the baldy head. Reporter: She believes if the bald juror knew anyone involved in trial, especially the wins, it should have disqualified him as a juror. The key point here is less about how much did he know about these people and more, D he intentionally lie to get the jury? Who was jury number 8? Juror 8 was jason.he knew M son's friends. Reporr: Setting her sights on that juror, a construction worker, still living at home with mom. He committed very serious juror misconduct a I've uncovered it. Reporter: Doreen, who at the time had beenried7 years, confides the details of her audacious Plano her husband, jukea's stepfather. He didn't want to do it. He said, no, no, no. Youent to a tanning booth? Yes. I just W trying to knock off some years. These pictures of her radical transformation were taken for a "Vanity fairagazine sot. I Bou whole new wardrobe, you know, lot blouses, push-u bra, high heels, that I had to practice walking in becau I wasn't good at it. Had to try ,ou know, attract hi You became your own price investator? Did. Sitting there for hours. Reporter: For months, she stakes out his everyove ihe little italyf Brooklyn. At one point, she E dons a burka. A Muslim friend hooks up with this burka and says, you can get up close to anyone you want and eavesdrop I remeer listening to a conversation, he was talking about bls. He liked blondes. That's what I decided to G really blonde. Reporter: Five months into the sting and she's ready to make her mov I rodey bike past him several times upnd down the block, waiting for him to not me. Then his friend wstled at me. Anmy heart dropped a I said hi. And I said I was from California and was new to th nborhood. And he said to give him a call. Reporter: Her new persona also rents a bachelorette pad. How long were you here? A year. Maybe a year and a ha Rter: Armed with a brand-new life and a sexy cover, she's ready for her next fla move. A roman dinner for two with juror number 8. You would have done whatever it took? Yes. Ven if it meant taking him to bed? Of course,fourse. But it didn't come to that? No. No.we had a iendship. Reporter: They Drinkwine, eat take-out and listen to the rolling stones while he was rolling something else. And you're smoking weed with Ilike, am I going to feel paranoid, am I goi to blow my cover? How much of your conversati were recorded? All of it. Yep. It turns out, in addition to her push-up bra and Daisy dukes, reen was wearing something else. A wire. And you kept it where? Between mybs. Llo? Hell I'm ous as hell. Sy she builds his trust ring the conversation towards her son's mud tile. He believed that John was jewish. Reporter: It's hardly Eno to a retrial, but then Doreen says herops a bombell. Is it finally the piece of evidence she needs to win her sos freedom?

This transcript has been automatically generated and may not be 100% accurate.

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