It would probably be more accurate to say that "policing" is something you - or others - say you don't want to do. But that's how the witnesses are understood. As what else? If your stake makes you a player in the upper ranks of policing, there's nothing you can do about being seen as such. Either you are a high-ranking witness or you are not. If you are, expectations are placed on you. You can reject them, but then you would also have to give up your position as a witness. Why don't you do it? If you are not interested in policing, you could give up your position as a Witness. What's stopping you?