I briefly looked for other information about this and I found this thread on the tor-talk mailing list. The thread mentions he contacted the torservers.net team for a recommendation about a lawyer. The thread also mentions someone is going to provide better proof soon.

https://lists.torproject.org/pipermail/tor-talk/2012-Novembe...

All tor node addresses are public. (Except for secret entry nodes.) I imagine this information could be used to verify claims.