Lots of abbreviations that "might" fit, but I doubt they do.
Administration Building (AB) might indicate the location they had the trial in.
Administrative Board (AB) could be some indication that this was addressed through some sort of administrative process
Above and Beside (AB) appears to be some vague legal term that I doubt applies, but it was one of the few that appeared to be legally related.
Answer Back (AB) is a military term indicating that you are required to answer back, so unlikely it's what is being used here.
Assembly Bill (AB) is another legal term, but I think it applies to legislation and not to trial cases.
So I'm not convinced it's any of these, but figured I'd throw them out as potentials, even if they're not good ones.