The United States court system is based on judicial federalism, in which judicial authority is shared between levels of government. The structure of the federal court system is outlined by Article III of the U.S. Constitution and statutory laws passed by Congress. States are given the authority to establish their own court systems.
State courts hear most day-to-day cases (and approximately 90 percent of all criminal and civil cases). State courts help the states retain their own sovereignty in judicial matters over their state laws, distinct from the national government.
Federal courts only hear cases that involve a “federal question” *(i.e., involve a federal criminal law, bureaucratic rule, etc., or raise the question whether some law or action violates the U.S. Constitution), interstate matters, and diversity of citizenship matters involving parties of two different states or between a U.S. citizen and a citizen of another nation (with a damage claim of at least $75,000).
State and federal court systems sometimes intersect and overlap each other. When concurrent jurisdiction exists between the federal and state court systems, there are alternative venues in which someone may appeal for assistance. Concurrent jurisdiction between federal and state court systems also means that there are different courts in which a person can face charges for a crime or violation. Double-jeopardy only protects the accused from being tried for the same crime in the same court system; it does not protect the accused from being tried of the same crime in a different court system.