JAMES COMEY: There are two things that matter in a criminal investigation of a subject: What did the person do and, when they did that thing, what were they thinking. When you look at the 100 years plus of the Justice Department's investigation and prosecution of the mishandling of classified information, those two questions are, obviously, present. What did the person do, did they mishandle classified information? And when they did it, did they know they were doing something that was unlawful? That has been the characteristic of every charged criminal case involving the mishandling of classified information.

I'm happy to go through the cases in particular. In our system of law, there's a thing called mens rea. It's important to know what you did, but when you did it, this Latin phrase, mens rea, means what were you thinking? We don't want to put people in jail unless we prove that they knew they were doing something they shouldn't do. That is the characteristic of all the prosecutions involving mishandling of classified information.

There is a statute that was passed in 1917 that on its face makes it a crime, a felony for someone to engage in gross negligence. So that would appear to say, well, maybe in that circumstance you don't need to prove they knew they were doing something that was unlawful, maybe it's enough to prove that they were just really, really careless beyond a reasonable doubt. At the time Congress passed that statute in 1917, there was a lot of concern in the House and the Senate about whether that was going to violate the American tradition of requiring that before you're going to lock somebody up, you prove they knew they were doing something wrong. So there was a lot of concern about it. The statute was passed.

As best I can tell, the Department of Justice has used it once in the 99 years since, reflecting that same concern. I know from 30 years with the Department of Justice they have grave concerns about whether it's appropriate to prosecute somebody for gross negligence which is why they have done it once that I know of in a case involving espionage. And so when I look the facts we gathered here, as I said, I see evidence of great carelessness, but I do not see evidence that is sufficient to establish that Secretary Clinton or those with whom she was corresponding both talked about classified information on email and knew when they did it they were doing something that was against the law. So given that assessment of the facts, my understanding of the law, my conclusion was and remains no reasonable prosecutor would bring this case. No reasonable prosecutor would bring the second case in 100 years focused on gross negligence. And so I know that's been a source of some confusion for folks. That's just the way it is. I know the Department of Justice, I know no reasonable prosecutor would bring this case. I know a lot of my former friends are out there saying where they would. I wonder where they were the last 40 years, because I'd like to see the cases they brought on gross negligence. Nobody would, nobody did. So my judgment was the appropriate resolution of this case was not with a criminal prosecution. As I said, folks can disagree about that, but I hope they know that view -- not just my view, but of my team -- was honestly held, fairly investigated and communicated with unusual transparency because we know folks care about it.

Previously:

The “Gross Negligence” Claim About Clinton Emails That The FBI Specifically Rejected

ABC's Dan Abrams Dismantles Conservatives' Claims That Clinton Was “Grossly Negligent” With Her Emails

Giuliani Keeps Pushing His Faulty Interpretation Of “Gross Negligence”