The dual court system is the distinction of state and federal courts that make up the judicial branch of government. Where a case does not involve the government or multiple states, the state court has been assigned jurisdiction as stated in the United States Constitution. There has been some talk of court unification at different points over the last century, but it has not taken place universally. The court system was not set up in one chunk and has, over time and in many different areas, been generated piece by piece. A primary factor to maintaining the dual-court system is the sheer cost and amount of time it would take for the U.S. Supreme Court or one governing body to hear and sentence every offence no matter how large or small.
Courts are an essential aspect of the criminal justice system. It is necessary to sustain separate systems, which include police, court, and correction, locally, at the state level, and federally, depending on the situation. If there were only one massive police force and corrections organization dealing with a monolithic court system, effectiveness would be minimal. All criminal activity requires a judge's presence and ruling after the individual has been arrested. It is far more efficient for each of the countless locations, nationwide, to have a municipal court system in place.