Patient that is under arrest and is unable to make medical decisions who makes the decisions to decide the medical care?

This person needs to have a Healthcare Proxy. This is someone who will make ONLY their medical decisions, and is court appointed. Usually the court will appoint a family member. A person who is under arrest still has the autonomy to make their own medical decisions, Only a person who is incompetent (determined by the court), or who does not have capacity (determined by a physician) can NOT make their own medical decisions. If you wish to become this persons health care decision maker, you need to seek the necessary forms to become their healthcare proxy (most hospitals have the forms or should at least be able to tell you how to get them).