Intriguing new evidence in the murder trial of former new England patriot Aaron Hernandez. How to shell casings and bubble gum allegedly link the former NFL star to the execution-style killing of his... See More
Intriguing new evidence in the murder trial of former new England patriot Aaron Hernandez. How to shell casings and bubble gum allegedly link the former NFL star to the execution-style killing of his friend? Here's ABC's Ron Claiborne. Reporter: Key evidence from prosecutors in the Aaron Hernandez trial. Surveillance footage at a gas station outside of Boston taken 90 minutes before prosecutors say he committed murder. The video, which shows Hernandez acting erratically, seeming to dance at the gas station. Where he buys blue bubble gum which investigators say could link him to the crime. It's just the latest in a mounting series of caught on camera moments the prosecution has shown jurors to build a timeline in their murder case against the former NFL star Aaron Hernandez. Orchestrated or participated in the killing, covered up the killing -- Reporter: Earlier this month Hernandez's former teammates celebrating football's greatest victory, the new England patriots super bowl win. The new England patriots! Are the NFL champions! Reporter: 25-year-old Hernandez was entering the first month of his murder trial. Memories of his $40 million NFL contract gone. The former tight end who pleaded not guilty was 23 at the time of the murder. A rising star in the football world. Second and a deuce -- Reporter: Scoring a touchdown in super bowl xlvi. Touchdown Hernandez! Reporter: Prosecutors say it all unraveled in June 2013 when police say Hernandez and two others picked up a friend, 27-year-old Odin Lloyd, who journeyman semi pro football player, and murdered him. The night began in Providence, Rhode Island, where Hernandes and a group of friends ran up a $243 bar tab at the south street cafe. The bar manager testifying in court today she saw Hernandez smoking marijuana. Mr. Hernandez and the other gentlemen were smoking on the corner of the street. When you say they were smoking, what were they smoking? I believe marijuana, that's where the smell was coming from. Reporter: He paid the tab and left without incident. Authorities say he stopped for gas shortly after 2:00 in the morning with a man resembling his co-defendant Carlos Ortiz and could be seen raising his arms and seeming to dance as he walks toward the store. Inside he buys cigars and blue bubblicious gum, the same type of gum authorities later found attached to a .45-caliber shell casing. Here's what's important about that. Remember, he bought blue bubblicious gum. There is a wad of blue bubblicious gum stuck on a .45-caliber shell casing. Reporter: Outside, a man resembling Ortiz appears to be wearing a white towel around his neck. Authorities say a white towel was also discovered at the murder scene. After this, prosecutors say Hernandez and two accomplices drove to pick up Odin Lloyd, then drove him to an industrial park where they shot him to death. When prosecutors showed jurors pictures of the victim's body, found just half a mile from Hernandez's home, the dead man's mother rushed from the courtroom in tears. Police have never found the murder weapon or the white clothes Hernandez was wearing that night. One thing I know is missing, that's Hernandez's clothing. Is that in the black bag? There's a lot of the speculation that the murder weapon may have been in the black bag. Reporter: That black bag also captured on surveillance video at Hernandez's home. His fiancee two days after the murder seen carrying a heavy-looking black trash bag from their shared home. Why is she taking trash bags of potential evidence out of the home? For Hernandez it's been a steep fall from athletic stardom and riches. You're thinking, he's headed for pro bowls and more super bowls. Instead, we look and see he could be very easily headed for life in jail. Reporter: Aaron Hernandez grew up in a rough Connecticut neighborhood and lost his father at a young age. That was very, very tough for him. At the age that it happened. And had a little bit of a tough upbringing. Both because of that and even before that. Reporter: Hernandez found refuge in his great talent. Football was something that he really loved. I think it gave him a little bit of a reprieve from maybe some of the other everyday challenges of life when he was around football he could forget. Reporter: In high school his talent obvious. He started getting calls from colleges, eventually recruited by the university of Florida. A bright future was his for the taking. If he could keep on the straight and narrow. But before he even played a game at Florida, he nearly lost it all. There are reports that Aaron Hernandez had an altercation at a bar called the swamp. Reporter: A police report from that 2007 incident surfaced recently. Hernandez had gotten into a fight with a bar manager over two drinks that Hernandez maintained he had not ordered. And guess who tried to come to his aid? According to the police report, squeaky clean college teammate Tim Tebow. Offering to pay for the drink. Instead, according to authorities, Hernandez punched the manager so hard his eardrum burst. He could have been kicked off the team and he wasn't. Reporter: Hernandez was never charged in that alleged assault and his career quickly took off. By the time he reached the NFL, even he insisted he had grown up. You get changed by the patriot way. Now that I'm a patriot, I'm living like one and making the right decisions. Reporter: Only three years into his run with the new England patriots, one stranlgic night changed everything. Just a stunning fall from grace. All self-induced. But one of those stories that for every one of those rags to riches kind of stories, a kid makes good, this is the opposite. This is the complete opposite. Reporter: Now, as prosecutors pile up evidence, his fate remains uncertain. Many people have asked me, do I think the state's got a lock on the case? Believe it or not, no, I don't. I believe that there is a mountain of evidence showing that Hernandez murdered Lloyd. Here's the problem. He's a sports superstar. Do I have to say O.J. Simpson? There's never a lock on any case. Ever. Reporter: For "Nightline," I'm Ron Claiborne in New York. After seeing that video, what would you be thinking about Aaron Hernandez if you were on the jury? Head to our Facebook page and join dat bate.
This transcript has been automatically generated and may not be 100% accurate.