The Beat & The Badge: Immunity Deals

A judge has cleared the way for a retrial of Raul Valle in the deadly stabbing of Fairfield Prep student James McGrath. Valle was acquitted of murder last year, but the jury deadlocked on four lesser charges. When you look back on the first trial, something still doesn't sit right with a lot of people...two other teens got immunity deals. How do immunity deals work, why are they offered, and how does it work when police have informants?