I doubt staties would take on a local jurisdiction case.

Nimmy - your best bet is to run a traceroute on his IP address to identify his ISP, then pass that information on to the local authorities and ask them to obtain a warrant for information release (although some will do it willingly) and contact the ISP for ownership records. It's not surefire, as some IPs are not static, but it's probably the best you've got without doing something questionable legally.

Also, although it was a joke, something in the vein of what Chaoswind mentioned isn't necessarily a bad idea. Don't go so far as lying, but feel free to mention that you've seen several questionable interactions online to them.

You can do so here: http://network-tools.com/