How the U.S. Supreme Court Works

Nine justices, thousands of petitions, and fewer than 100 cases a year. Here's how the nation's highest court picks its cases and makes decisions.

The Supreme Court has the final word on what the U.S. Constitution and federal law mean. Its decisions can reshape everything from elections to health care to free speech, which is why its rulings dominate the news each June. Here's how the Court actually works.

Who sits on the Court

The Constitution creates the Supreme Court in Article III but does not set its size. Congress does that by law, and the number has been nine — one Chief Justice and eight Associate Justices — since 1869. Justices are nominated by the President and must be confirmed by a majority vote of the Senate. They serve "during good behaviour," which in practice means for life unless they retire, resign or are removed through impeachment.

How the Court chooses its cases

Most cases reach the Court when a losing party files a petition for a writ of certiorari, asking the justices to review a lower court's decision. The Court receives thousands of these petitions each year but typically agrees to hear fewer than 100.

Under a long-standing practice called the "rule of four," the Court takes a case if at least four justices vote to hear it. The justices often look for cases where lower courts disagree with each other on an important legal question, or where an issue has major national significance.

In a small number of cases, such as disputes between two states, the Supreme Court has original jurisdiction and hears the case first, without any lower court.

The Court's calendar

The Court's term begins on the first Monday in October. Oral arguments are usually held from October through April. Decisions are released throughout the term, but the biggest and most divided cases often come at the very end, in late June or early July.

Briefs and oral argument

Before argument, each side files written briefs laying out its legal case. Outside groups that are not parties can also file "friend of the court" (amicus curiae) briefs. At oral argument, lawyers for each side usually have about 30 minutes, though the justices frequently interrupt with questions — and those questions are often reported as hints about how the Court may rule.

How decisions are made

After argument, the justices meet privately in conference and take a preliminary vote. If the Chief Justice is in the majority, he assigns who writes the majority opinion; otherwise, the most senior justice in the majority does. Draft opinions circulate, and justices can change their votes before the decision is final.

A decision can include several kinds of opinions:

• Majority opinion: the Court's official ruling and reasoning, which becomes binding precedent.
• Concurring opinion: written by a justice who agrees with the outcome but for different or additional reasons.
• Dissenting opinion: written by a justice who disagrees with the outcome. Dissents have no legal force, but some have later influenced the law.

The power of judicial review

The Court's power to strike down laws that conflict with the Constitution — known as judicial review — was established in the landmark 1803 case Marbury v. Madison. It is the reason Supreme Court decisions can overturn acts of Congress, actions by the President and state laws.

The "emergency docket"

Beyond its regular cases, the Court handles urgent requests — for example, to pause a lower court's ruling while an appeal continues. These are decided faster, often without full briefing or oral argument, and are sometimes called the "emergency" or "shadow" docket. They have drawn growing public attention in recent years.