State's Attorneys utilize Supervisory Assistant State's Attorneys in the G.A. courts. State prosecutors only have jurisdiction over state criminal offenses. Federal prosecutors have jurisdiction over criminal statutes enacted by Congress. Their jurisdiction operates independent of any state laws. State prosecutors do handle cases in federal courts, including the Supreme Court of the United States, but these are usually federal actions attacking a state conviction.
Prosecutors rely on police officers to investigate an allegation that someone has committed a crime.
In many cases, the police make an arrest at the scene of a crime. The arrestee is then presented to the court to determine if there is probable cause to believe that he or she committed the crime charged by the police. The prosecutor thens determines whether to proceed with the case. In other cases, prior to any arrest, the police provide the collected information to the prosecutor who, considering all of the evidence and the law, decides whether there is probable cause to believe that a crime has been committed and that a person or persons committed it. The prosecutor may decline to prosecute if, for example, there is insufficient evidence to prove a crime has been committed or to prove who committed the crime.