I highly doubt that he would've gotten the death penalty, they bluffed him. It was another mobster first of all. Second of all, even if it was an innocent person, this is NY we're talking about, not Texas. If he was truly facing the death penalty, it would've been reduced to life in prison without parole for his cooperation. But they let him free. They didn't even need his cooperation, it was all about humiliating the mob.