Who can be appointed guardian in Missouri for someone who has been found to be incapacitated? In Missouri, a guardian is someone who is appointed by the court to manage the affairs of someone who has become incapacitated. Incapacitated is a legal definition meaning that the person can no longer either decide what they want in terms of where they live or what doctor they are going to see, or they cannot communicate their wishes where they need someone else to step in and do that for them.