I'd provide whatever records the warrant or court order specified **to the best of my ability.** If the data doesn't exist it can't be provided and nobody can wish it into existence. And with most (all, as far as I know) library autormation systems not collecting a history of what a patron checks out, the data wouldn't be there to provide.

Check out your state laws: most have laws which protect the privacy of library circulation records (such as those records are).

Were I one of the nasties, I'd worry more about the web-based email I sent from the library's public computers. THAT can be intercepted and read from servers outside of the library, or, WITH THE PROPER WARRANTS, copies diverted to the authorities as it is sent from the library's servers (picture a Y, with one branch going to the FBI and the other to the person addressed).

There is NO privacy on either the World Wide Web OR the Internet in general. NONE. ZIP. NADA. ZERO. Even encrypted messages can and have been broken. If you want to send a private message, send it via the post office and put cello tape over the envelope flaps (might not keep it private, but makes it much more difficult to open undetected, according to MI5).

And, by the way, cell phones are one of the LEAST secure means to send info. Use a land line -- but even there privacy is relative.

Lep is right: local cops, even state cops, aren't likely to want to check out library records except in extraordinary circumstances. A gung-ho FBI rookie is a different story, however.