In December of 2002, NBC News producer Dan Slepian got a letter from a New York state prison. It was from a man serving 25 years to life for murder. And it ended with a desperate plea: look into my case. Jon-Adrian JJ Velazquez had been convicted of killing a retired New York City police officer, but he insisted he did not do it. Dan was skeptical. Prosecutors said five eyewitnesses had sworn JJ was the killer. Could five people be wrong? Letters from Sing Sing tells the story of a man convicted of murder, a journalist, and the letter that changed both of their lives.