In December of 2002, NBC News producer Dan Slepian got a letter from a New York state prison. It was detailed and meticulous, almost like it had been written by a lawyer. But it wasn’t. 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 didn’t do it. Dan was skeptical. Prosecutors said five eyewitnesses had sworn JJ was the killer. Could five people be wrong?

But JJ was adamant about his innocence. He had devoted years to fighting his case, spending hours in the law library, poring over every page of his file. He was confident that if Dan looked into it, he’d see the truth. He even challenged Dan to prove him guilty.

So Dan began to dig. What he discovered went far beyond just JJ’s case. And 20 years later, it’s still unfolding.

Letters from Sing Sing tells the story of a man convicted of murder, a journalist, and the letter that changed both of their lives. New episodes drop every Monday through March 27, 2023.