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"20/20 SATURDAY" - THE MYSTERY ON JOHNSBURG ROAD

"20/20" Follows Twists and Turns as a Murder Mystery Unravels, Airing Saturday, March 7, 8 PM ET on ABC

How does a man wind up being convicted of committing a murder at a grocery store when no body, no weapon, and no DNA link him to the scene? That is exactly what happened to Mario Casciaro in 2013 when he was convicted of killing 17-year-old Brian Carrick, who was Casciaro's former co-worker and fellow stock boy 11 years earlier. Casciaro is now serving a 26-year sentence.

Prosecutors were successful in getting a conviction on the very rare and controversial charge of murder by intimidation because another stock boy, Shane Lamb - in exchange for an immunity deal - told prosecutors he knocked Carrick out during a fight, and then left Casciaro with the unconscious Carrick. Yet could potentially explosive evidence, including Shane Lamb's recent recanting of his story, help Casciaro prove his innocence? "20/20" follows the clues as the mystery unravels. ABC News Correspondent Ryan Smith's report includes exclusive prison interviews with Mario Casciaro, who never testified in two trials, and Shane Lamb, who is behind bars for an unrelated crime. "20/20 Saturday" airs MARCH 7 (8:00-9:00 p.m., ET) on the ABC Television Network. (OAD: 10/3/14)

"20/20" is anchored by Elizabeth Vargas and David Muir. David Sloan is senior executive producer.