Typically known as a district attorney, state's attorney, or United States attorney. He who prosecutes another for a crime in the name of the government.
Prosecutors are public or private.
A private prosecutor is one who prefers an accusation against a party whom be suspects to be guilty. The prosecutor has an inducement to prosecute, because he cannot, in many cases, have any civil remedy until he has done his duty to society by an endeavor to bring the offender to justice. In Pennsylvania a defendant is not bound to plead to an indictment where there is a private prosecutor, until his name shall have been indorsed on the indictment as such, and on acquittal of the defendant, in all cases except where the charge is for a felony, the jury may direct that he shall pay the costs.