A district attorney (DA) is an elected official who oversees the prosecution of state criminal cases in a county. The DA sets criminal justice priorities for the county. If you care about local criminal justice policy, this is the role that will influence that most heavily at a local level. DA's are elected every four years, and do not have any term limits. DA's lead a staff of prosecutors, most commonly known as assistant district attorneys. The DA’s office is responsible for working with police and witnesses to investigate crimes, to decide whether or not prosecute, and, if the case goes to trial, to attempt to prove that a person suspected of a crime is guilty beyond a reasonable doubt.