I don't know why you would want out of jury duty given that it is the only time the individual has any significant say in the system. But, if you are a lib, then the way out is to say things like you know one or more parties to the action (lawyers, defendant, plaintiff, etc.) You might also say you have already decided the matter in your own mind. But, if you don't want a chance to nullify bad laws, bear in mind that people are willing to keep you living under a bad government because of your actions.