In federal criminal court, the United States prosecutes offenses defined by federal law. A state prosecutes violations of its own criminal law in state court. Most everyday crimes, family disputes, probate matters, and ordinary contract claims are handled in state systems because state courts possess broad general jurisdiction. Federal courts hear the categories assigned by the Constitution and Congress.

The parties' names offer a clue. In a criminal prosecution, the sovereign brings the case against a defendant and must prove guilt under the applicable criminal standard. In a civil action, a plaintiff seeks relief from a defendant, and the burdens and remedies depend on the claim. Government can also be a civil plaintiff or defendant, so the presence of "United States" does not alone make a case criminal. Look for prosecution and punishment rather than relying only on a party label.

Civil procedure also distinguishes the claim from the remedy. A plaintiff may seek money damages, an injunction ordering or forbidding action, or a declaration of legal rights. Winning a constitutional argument does not automatically establish every requested remedy; standing, immunity, statutory causes of action, and remedial rules may matter. Criminal defendants receive constitutional procedural protections, but a civil label does not make constitutional limits disappear when government is a party.

One event can generate both kinds of proceeding. A fraudulent contractor might face a federal criminal prosecution brought by the United States and a separate civil action seeking repayment or damages. The proceedings have different claims, burdens, and remedies even though they arise from the same conduct. Likewise, acquittal in a criminal case does not automatically decide every possible civil claim, because the legal questions and burdens may differ.

Federalism can permit separate sovereigns to enforce distinct laws, but beginners should avoid assuming that any second prosecution is automatically valid or invalid. The safe classification is narrower: identify the sovereign, source of law, alleged violation, forum, and requested consequence. Later doctrine determines whether a particular constitutional limit applies.

Worked classification. The United States charges a defendant with federal tax fraud: federal criminal case. A worker sues an employer under a federal employment statute: federal civil claim. Neighbors dispute a boundary under state property law: ordinarily a state civil case. Classify the sovereign bringing the action, the law creating the claim, and the remedy or punishment—not simply the courthouse pictured in the question.

Video lesson: Structure of the Court System: Crash Course Government and Politics #19