On the Saturday episode of Slate’s Supreme Court podcast, Amicus, Dahlia Lithwick spoke with Mimi Rocah, who is Pace Law School’s distinguished fellow in criminal justice. Rocah previously served as an assistant U.S. attorney in the Southern District of New York from 2001–17. In her role, Rocah successfully prosecuted and tried cases, including some high-profile organized-crime cases, so she joined the show to talk about the Mueller probe and to help us do a little sorting of forest from trees.

A transcript of their discussion, which has been condensed and edited for clarity, is below.

Dahlia Lithwick: We thought we’d start this show with the swirling legal story of the endlessly complicated Robert Mueller probe. It now seems to be accelerating. It’s heating up in what I think we could probably just call the Special Counsel December Advent Calendar, where every single day we get some new revelation. So, I think what I want you to do is help us with this one mystery question, which is collusion, because, you know, the president, he likes to tweet, “No collusion, no collusion,” but as you know better than anybody, there’s not really a thing that is collusion. Can you help us understand what comes into the bucket, to the extent that the president is accused of colluding, or people in his campaigns are accused of colluding? What are the conspiracies that we’re talking about?

Mimi Rocah: First of all, I think that you said it correctly. It’s not collusion. It’s really conspiracy, if we’re talking about looking at it from the legal framework, because there is no charge of collusion. But there are certainly charges of conspiracies, and conspiracies can take many different forms. Just to get in the weeds for a second: There’s Statute 18 U.S.C. 371 and it has two different kinds of conspiracy. One is a criminal agreement to commit a crime. So, for example, if we agree to rob a bank and we take steps to further that, we’re committing a crime under that statute.

Then there’s a separate one, which is conspiracy to defraud the United States, and that basically says that you commit a crime against the United States when you interfere with a proper functioning of the laws of the United States. So it’s similar, but a little bit different. It’s much less frequently used. I don’t think I’d ever charged anything under that prong, but it’s a perfectly legitimate statute that’s there. In fact, I think a judge recently upheld it in Concord Management—the case against some of the Russians that Mueller has already charged—upheld it as a valid theory.

I think by charging it under that conspiracy prong, Mueller really captures the purpose of the acts and the individual crimes that people are committing. What we’re starting to inch closer toward and understand a little bit more is, were there American citizens, people here who were involved in those kinds of crimes in different ways, small or large?

Lithwick: So I’m gonna ask you something totally unfair, which is when Donald Trump tweets, They tell me there’s no collusion. I know there’s no collusion. My lawyers say no collusion. What does he mean, do you think? What does that mean to him?

Rocah: Well yeah, I’ve been saying this actually since he first started tweeting. I think first of all, Trump has no idea what the conspiracy law means and how it works. So when he says, It’s a witch hunt, no collusion, what he was actually saying is, I had no phone calls. I had no meetings. I didn’t do this. And I think he may actually believe that as long as he didn’t do that, and this is common. I mean, we should point out this is common amongst criminals.

I can’t tell you how many people, cooperators I met with, who thought they hadn’t done anything wrong because they hadn’t actually had face-to-face or phone-to-phone conversations or email contact with the other person whom they were charged in a conspiracy with. It took a while. It would take a while in those proffer sessions to explain to people. You don’t have to. That’s not how conspiracy law works. This is a widely used law that is very broad and you can actually join a conspiracy with someone you actually have never even met. That’s sort of the point of the law, right? It’s to capture whether you’re working toward a common scheme. So I think Trump doesn’t understand that even if he didn’t know, let’s assume for a moment, every part of what was going on here: how they were going to throw the election, or when exactly that was going to happen. As long as he had some idea of the understanding of the broad purpose of what they were doing and he did something, anything material to sort of facilitate that in some way, that could put him in that conspiracy.

“I can’t tell you how many people thought they hadn’t done anything wrong because they hadn’t actually had conversations or contact with the other person whom they were charged in a conspiracy with.” — Mimi Rocah

So again, we don’t know all of the facts, but I think he has a fundamental misunderstanding of the law. So, when he says no collusion, he’s actually talking about very specific conduct that may be true. That may be actually right that he didn’t have phone calls with Russians about hacking the emails and throwing the election, but that’s not what’s required under the law.

Lithwick: And I just wonder because, as you’re talking, I’m thinking: But this is what makes it so easy to say “witch hunt, witch hunt,” right? Isn’t the breadth of it the very thing that allows Trump and his defenders to say, oh my god, Mueller has a license to tag anyone who ever talked to anyone about anything and that’s the problem with these really broad conspiracy laws?

Rocah: Well look, I mean, without getting into sort of a constitutional analysis of the conspiracy, first of all, I think it’s fair to say people are charged and convicted under this law every single day, all across the country. So Trump isn’t being sort of put under a microscope that every other American citizen isn’t who gets investigated for a crime. He happens to have a really good prosecutor holding that microscope, Robert Mueller, but it’s a very widely used law.

Second of all, there are knowledge requirements. So you don’t have to have direct contact and phone calls and things like he seems to be thinking, but you do have to have knowledge of what is going on, so to speak, and what this scheme is and the goals of it, and further it in some way. You can’t just be passive. You wouldn’t be charged if you were just a passive participant or were being duped in some way.

And third, I think the facts as they’re starting to play out here really show us that Trump and people around him were much more invested in this than he’s certainly letting on and even than some of us who have been following this previously understood. So for him to say, it’s a witch hunt because I didn’t know it was going on, I think is really not going to be borne out by the facts here.