a. Res judicata is a Latin term which means a issue or matter have already been decided in court of a competent jurisdiction that should not be re-open or re-contest by the same parties. This principle usually apply to civil matter and a rarely use in criminal matter. Also the parties in the proceeding are prevented or being stop from challenging the matter again in the same court. However the issue doesn’t come into valid if one of the parties appeals to the next higher court.