We caught a pedo. Twice. What to do?

Question

About a year ago we received a report from one of our users that they were getting inappropriate messages from another user. Upon investigation, we found child-grooming behaviour from the offender towards 20+ other users (female, under 18).

Of course, the immediate action was to summarily ban the offender's account. We also found plenty of personal information shared in the messages to various young girls, enough to confidently identify him. We found his Facebook profile, a few other profiles, and his picture on a list of registered sex offenders. Nice.

So we contacted police local to this guy, and the FBI, passed on the information, and were told it would be investigated. There were some follow-up questions, we answered those, then radio silence so we just kind of moved on and figured they had it in hand.

He came back.

Same guy, different (but similar) GMail and username (containing a shortened version of his real name), same behaviour.

Once he was brought to our attention, we banned him again, and now he's contacted our support centre to try and dispute the ban.

I promise you that I did not mean for any inappropriate behavior. I know that this is a child friendly site.
I don't remember when I used Inappropriate Behavior.
Please forgive me and I'll do better next time, I really love [website]. I really want [website] back. It's the best thing ever to happen for me. Please forgive me. 

So clearly contacting the FBI didn't work. What exactly are we supposed to do here? Do we just report him again? How can we expect any better this time? Do we respond to him saying "Look, we know who you are, we know what you did, knock it off, you're not welcome here"?

We're at a loss. Please help.

Answer 1

1. Definitely don't talk to him about knowing who he is/that you contacted FBI. He will understand his "mistake" and fix it for the next time.
2. Contact FBI and police again, probably ask what is going on. They have unlikely forgot about him, and it is likely that they will benefit from your help.
3. Tell him some nonsense about his ban, probably just answer not-so-often, probably tell that you do not disclose the exact proof of his bad behavior in order to keep your investigation methods secret. The last thing is a very good tool against such people.

Answer 2

I would NOT level with him that you know who he is. All that will do is let him know that you have the ability to recognize who he is and try to figure out ways to be less obvious next time.

What you can do is a) report it again. There may not have been enough to go on at the time, but if he's doing more, it's new information. It might still not be actionable, but it doesn't hurt to have it in a file somewhere. Investigations can also take time to build a case, so it may still be ongoing. b) Inform him of the reason for the ban for the behavior of this version of the user and inform him that you contact the FBI with relevant details for infractions of this kind. That should probably scare him off without having to reveal that you know who he is, so if he does try to come back, you'll be more likely to be able to identify him again.

Answer 3

In addition to the answers you already received:

Make sure you keep backups of all information that you have on his activities on the site, both the first and the second time. Keep the email correspondence.

The authorities may want it as evidence.

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One additional warning: do not take any action against him yourself (1), other than what is in the scope of your site (blocking him) (2).

(1) No naming and shaming, sending out blanket warnings etc. Police and the judiciary are the people who have to handle this, and the people who have more background knowledge (available) than you do (what actions are legally possible, why he is on the s.o. list, etc.).

(2) Don't go into discussions with him; ultimately you are the ones who say who has access to the site. (This is essentially point 3 in Dmitriy's answer).

Answer 4

I haven't been in exactly the same situation but in my (fan fiction) community people primarily communicate as characters, so while we sometimes do end up finding out people's real names, we often have banned members sneak back in simply by changing their name and email.

We have two main filters for this: First, and primarily, is the IP address. Although it's easy for a savvy user to get around this by using a VPN or whatnot, most have no idea how to circumvent IP address tracking, and don't know that we are using it anyway. Although we mention in our privacy policy that we track IP addresses, I doubt most read that, and we don't advertise it anywhere else. Our forum software automatically tracks IP address, and every form on our website tracks it (without saying so) as well.

Second, suspicion! In our experience, banned members fall into two groups: The ragequits and the determined. The former hate us with the fury of 1,000 suns after being banned and then leave either to go start their own thing, or to never be heard from again. But on the way out, they make as much of a mess as possible.

The latter – the determined – simply find a way to keep coming back. We've had people who have been banned who've continued coming back into the group for years – they join innocuously enough, and then at some point their behavior veers into the territory that got them banned in the first place and/or they start blabbing to new friends about how they're a former member and/or they just make a mistake that gives us a peek behind the curtain. But we simply keep a skeptical eye out for any behavior out of the ordinary. So, for example, our group has a very specific, very unique writing format. And when people on our application know it already, it's a huge red flag that they're a former member, so we run a quick IP check, search for the email address and variations, in our records, etc. Even if we can't make a match, we keep a hawk eye on them after that looking for any small mistake that might give away their game.

So bottom line, for me, is that you really can't rely on law enforcement. You simply have to play the whack-a-mole game, be strident and merciless about re-banning those who have been banned before, and ask your members to be vigilant for anything out of the ordinary.