Some state and county court systems also call special prosecutors to handle high profile cases. Sometimes the regular prosecutors have to take themselves off a case because of a personal or professional connection with the defendant, too.
My wife had to testify in a local murder trial that was receiving national media attention. The special prosecutor was a state-level attorney who had a high conviction rate. He tried some legal tactics that were a little questionable, but he did get a conviction during the first trial. A judge later overturned the verdict, citing prosecutorial misconduct. The special prosecutor failed to reveal the existence of an FBI report to the defense attorneys.