In The Gotti Wars: Taking Down America’s Most Notorious Mobster (Scribner, May), former prosecutor Gleeson recounts the inside story of the federal prosecutions of the so-called Teflon Don.

Your second, successful prosecution benefited from the decision of John Gotti’s underboss, Sammy Gravano, to cooperate with you. Can you discuss why you kept your deal with Gravano a secret from your boss, U.S. Attorney Andrew Maloney, until it was finalized?

It’s not intended to disparage Andy, who I’ve loved, and he was a great boss, and he knew how to delegate and to trust. But the guy famously had drinks every night with the lions of the New York City bar, his friends. What if it slipped that the underboss of the Gambino family was talking to us about flipping? Pre-9/11, these guys were Public Enemy Number One. It would have ended everything. There was no reason he had to know.

Do you understand why Maloney’s number two said she’d have fired you for that, if it was her call?

Now I’m a partner in a law firm, and an associate here doesn’t sharpen the pencil without the partners knowing about it. So I understand that I was like an associate, striking the biggest deal in modern history, leaving out my bosses. I understand her perspective now better than I did at the time. I mean, but not for nothing, it was a good deal. It brought down the mob.

Do you think you’d have still convicted Gotti without Gravano’s testimony?

We had a really good case, but it was one-dimensional, it was voices on recordings. The benefit to that was you can’t cross-examine a tape, so that’s good from a prosecutor’s standpoint. The downside was it lacked depth, right? You don’t want to put on an FBI agent to just basically spin the tapes.

What do you think the investigation’s legacy has been?

It broke the back of the mob as we knew it then. It brought the full power of the FBI down on all of organized crime. There were eight separate squads in New York then investigating it. Now there’s one squad, only half of which investigates organized crime. Gravano wasn’t your average gangster. He was regarded in the mob as the real deal—he was in the mob for 30 years. When Sammy flipped, mobsters thought, there must be something wrong with this thing of ours, and that was meaningful. After he flipped, we couldn’t keep the mobsters who wanted to be witnesses away from our door with a stick.