The striking thing is that this is a subpoena to provide evidence in a criminal investigation. If it had been a subpoena related to a civil libel lawsuit, then either Twitter or the anonymous poster could try to quash the subpoena, and then the court would have to decide whether the plaintiff had, at least, a legally sufficient libel case (i.e., the statements were factual allegations and not opinions, and there was some reason to think the factual allegations were false). If the plaintiff did have such a case, then the plaintiff would indeed be able to discover the identity of the defendant, so he could know whom to sue, and so he could get further factual information relevant to the case (such as what the defendant knew about whether the statements were true or false). That’s the emerging rule in many states (though there are important variations in detail). There are no Pennsylvania appellate cases on the subject, but I expect that Pennsylvania courts will follow this rule, as several Pennsylvania trial courts in fact have.
But this is a grand jury subpoena, so presumably the theory is that the subpoenas are relevant to some criminal investigation. My sense is that one should be able to quash such a subpoena as well, if there is no legally sufficient basis for the investigation, or for the conclusion that the information would be relevant to the investigation. Yet that requires us to know what is being investigated. It can’t be an investigation of libel, since Pennsylvania doesn’t have a criminal libel statute. In principle, since some tweets from the relevant twitterers might be read as accusing Corbett of criminal misconduct, the twitterers’ identities might be relevant so they could be asked for further evidence of such misconduct. But I have no reason to think that Corbett is indeed being so investigated.
So this looks like an interesting case; I hope Twitter does move to quash the subpoena, so we can get some better sense of whether the subpoena indeed has a legal basis. And if you have any further information you can share about the underlying investigation, please let me know. Thanks Steve Piercy for the pointer.