can inmates talk about their cases in letters

Yes, they can. Most outgoing mail in not disturbed. The incoming mail is read however. We would still caution your inmate about putting too much information in a letter. If the case has not been tried yet, we think a better option would be to mark those type of letters "LEGAL MAIL" at the top and bottom of each letter. That would protect the inmate's privacy and if the contents of the letter were to be obtained, the court would have to disallow it as evidence.