In many jurisdictions in the United States, a District Attorney (DA) is an elected or appointed government official who represents the government in the prosecution of criminal offenses. The district attorney is the highest officeholder in the jurisdiction's legal department and supervises a staff of assistant (ADA) or deputy district attorneys. Similar functions are carried out at the local level in other jurisdictions by officers named the Commonwealth's Attorney, State's Attorney, County Attorney, or County Prosecutor. Depending on the system in place in the particular state, county, or district attorneys may be appointed by the chief executive of the region or elected by the people.
The District Attorney didn't do a good job in convicting O. J. Simpson.