A few months ago, we had a question about what would happen if necromancy was possible and an undead was called as a court witness. I gave a rather fun-to-write, tongue-in-cheek answer, which might be germane to your question too. Here’s just a snippet:

So now we come back to zombies. Would a jury be able to set aside their shock, horror, and awe about a zombie in court that they could focus on being the finder of fact? If a zombie says they’re an eye-witness to a mugging, would their lack of actual eyeballs confuse the jury? Even more confusing would be a zombie that is testifying as an expert witness. Does their subject matter need to be recent? What if the case needs an expert on 17th Century Parisian fashion and the undead is from that era and worked in haute couture? Are there no fashion historians who could provide similar expert opinions?