The laws of the United States are a complex tapestry weaving through history, sometimes vague, sometimes specific and often confusing. It's up to the federal judicial system to sort through this web of legislation and decide what is constitutional and what is not.

The Supreme Court
At the top of the pyramid is the United States Supreme Court, the highest court in the land and the final stop for any case that has not been settled by a lower court decision. Supreme Court justices-eight associates and one chief justice-are appointed by the president of the United States and confirmed by the U.S. Senate. Justices serve for life or until they choose to step down.

The Supreme Court hears a select number of cases that may have originated either in lower federal courts or in state courts. These cases generally hinge on a question of constitutional or federal law. By tradition, the Court's annual term begins the first Monday in October and ends when its docket of cases is finished.

Landmark Cases of Constitutional Review
The Supreme Court has dispatched some of the most important cases in U.S. history. The case of Marbury v. Madison in 1803 established the concept of judicial review, defining the powers of the Supreme Court itself and setting the precedent for the court to declare acts of Congress unconstitutional.

Dred Scott v. Sanford in 1857 determined that African Americans were not considered citizens and thus were not entitled to the protections afforded to most Americans, though this was later overturned by the 14th Amendment to the Constitution.

The decision in the 1954 case of Brown v. Board of Education abolished racial segregation in public schools. This overturned an 1896 Supreme Court decision, Plessy v. Ferguson, which formalized the long-held practice known as "separate but equal."

Miranda v. Arizona in 1966 required that upon arrest, all suspects must be advised of their rights, particularly the right to remain silent and to consult with an attorney before talking to police. The 1973 Roe v. Wade decision, establishing a woman's right to an abortion, has proven one of the most divisive and controversial decisions, one whose reverberations are still felt.

The Lower Federal Courts
Beneath the Supreme Court are the U.S. Courts of Appeals. There are 94 judicial districts divided into 12 regional circuits, and each circuit has a court of appeals. These courts hear appeals from within their respective districts as well as from federal administrative agencies. The circuit courts also hear appeals in specialized cases such as those involving patent or trademark laws; those decided by the U.S. Court of International Trade, which hears cases involving international trade and customs issues; and those decided by the U.S. Court of Federal Claims, which hears cases involving monetary claims against the United States, disputes over federal contracts, federal claims of eminent domain and other claims against the nation as an entity.

District courts are the trial courts of the U.S. judiciary. Here, unlike in the higher courts, there may be juries who hear cases and render verdicts. These courts hear both civil and criminal cases.

• Government 101 Index

Phaedra Trethan is a freelance writer who also works as a copy editor for the Camden Courier-Post. She formerly worked for the Philadelphia Inquirer, where she wrote about books, religion, sports, music, films and restaurants.