Describe the structure of the federal court system, explain judicial review and its origin in Marbury v. Madison (1803), and outline how a case reaches the Supreme Court.
Article III establishes "one supreme Court" and lets Congress create additional lower federal courts as needed -- Congress has built a three-tier system: U.S. district courts (trial courts, where cases are first heard), U.S. circuit courts of appeals (which review district court decisions for legal errors), and the Supreme Court at the top, currently made up of nine justices, a number set by Congress rather than fixed in the Constitution itself. Federal judges, including Supreme Court justices, are nominated by the president and confirmed by the Senate, and then serve "during good Behaviour," in practice a lifetime appointment unless impeached. This lifetime tenure is a deliberate design choice: it insulates judges from short-term political pressure and public opinion, so that unpopular but legally correct rulings do not cost a judge their job.
Nowhere does the Constitution's text explicitly grant courts the power to strike down a law as unconstitutional. That power, called judicial review, was established by the Supreme Court itself in Marbury v. Madison (1803). William Marbury had been appointed a judge in the final hours of President John Adams's term, but his commission was never delivered before Adams left office; the new administration, under President Thomas Jefferson, refused to deliver it. Marbury sued, asking the Supreme Court to order delivery under a power Congress had given the Court in the Judiciary Act of 1789. Chief Justice John Marshall's ruling was a masterstroke: he agreed Marbury deserved his commission, but ruled that the specific section of the Judiciary Act letting Marbury sue directly in the Supreme Court was itself unconstitutional, exceeding the Court's authority under Article III. The immediate result gave Jefferson's administration what it wanted, no commission for Marbury, while establishing something far more important long-term: the Supreme Court's power to declare an act of Congress unconstitutional. Today, the Supreme Court controls almost its entire docket by granting or denying a writ of certiorari; by informal custom, at least four of the nine justices (the "Rule of Four") must agree to hear a case, and the Court denies the vast majority of the thousands of petitions filed each year.
Mastery looks like: They can explain judicial review and its origin in Marbury v. Madison, describe the three-tier federal court structure, and explain why judges have lifetime tenure and how a case reaches the Supreme Court.
Common stumbles: Assuming judicial review is explicitly written into the Constitution's text rather than a power the Court established for itself in 1803, or assuming the Supreme Court hears any case it wants immediately rather than through the certiorari process.