History
The Special Prosecutor and Independence of Executive Investigations
Quick fact
Special prosecutors are not a permanent institution but are typically appointed only when the Department of Justice has a conflict of interest, such as when the president or a senior official is under investigation. The most famous holder of this role, Ken Starr, spent millions investigating President Bill Clinton, but the office was allowed to lapse after that.
Why this is interesting
Imagine the person accused of a crime is the one who controls the police force. How can justice be served? That's the puzzle the special prosecutor was designed to solve.