I assume you mean that the harassment/stalking was allegedly taking place on Wikipedia. IANAL but I do help prep civil cases, and the documentation listed below would be the bare minimum of what would be requested. I don't know about Missouri, but pretty well any court in Canada would grant subpoenas for most of these documents.
For the prosecution it would involve the records of the Foundation that contained information about the editor who carried out the stalking/harassment (userpages, real names if known, IP addresses and whatever information is available to checkusers, etc), and any documentation showing actions taken in relation to the harassment. The contributions list of the editor, deleted versions of pages, deletion logs, block logs, and (if applicable) oversight logs are the most likely to be subpoenaed. All prosecution evidence must (eventually) be turned over to the defense.
On the defense side, they could well request subpoenas for the names and identities of editors/admins/checkusers who responded to the harassment or alternatively elected not to respond to the harassment (again, userpages, real names if known, and all info available to checkusers). The defense would probably have to show cause to get this information, but all they would likely need are printouts of diffs showing the username and the nature of the intervention.
Either prosecution or defense may request all available personal info on the alleged victim; they might go after all of the contributions of the alleged victim as well.
Somebody would probably be subpoenaed to testify on Wikipedia's policy about harassment and how it is enforced. That could be very, very interesting.
Risker
The burdens of discovery, testimony, and potential, including criminal, liability are not the reason to have and enforce a harassment policy. The best reason is to support our users and make a reasonable effort to protect them from harassment both on and off site. As one can see from the case of Megan Meier ([[Megan Meier suicide controversy]]), some people are quite vulnerable.
Fred