The U.S. Supreme Court receives 7,000 to 8,000 requests each year to hear appeals from state and federal court decisions. It hears arguments in only about 80 of those cases.

It was not always this way.

When the court was first established in the late 1700s, it was the only federal court authorized to issue final decisions in cases appealed from lower courts. This meant that the Supreme Court had to decide every appeal made to it. In the early years of the United States, that did not result in an excessive number of cases. But as the country grew, the number of appeals to the court became overwhelming.

In 1891, Congress created permanent courts of appeals (also referred to as circuit courts), which could make final decisions on appeals from federal trial courts (also called district courts). This lessened the Supreme Court’s judicial workload somewhat, but the court still had to accept or deny all cases presented to it.

The 1891 Act also created a new process for parties to seek review in the Supreme Court. Parties to a case decided by a lower court could seek a writ of certiorari (today typically referred to as “cert”). A writ of certiorari is a formal petition to the court asking it to take a case, which the court could then choose whether to grant.

A major change occurred with the 1925 Judiciary Act, shepherded by Chief Justice William Howard Taft, a former president of the United States who was appointed to the court by Warren Harding in 1921. Taft’s proposal was that the court could control the federal cases it would take through a writ of certiorari. After lobbying by Taft and a number of the justices, including Sutherland namesake Justice George Sutherland – and support from President Calvin Coolidge – the bill eventually passed Congress.

The court still had to accept some cases through appeals, such as state court decisions on federal constitutional issues. This exception existed until Congress made certiorari virtually the only way to secure Supreme Court review in 1988. (Many of the appeals were resolved in one-sentence decisions until that time.)

How does the court determine which cases to grant cert on?

The first and most basic criterion comes from the Constitution itself. Article III gives the court authority to hear appeals “that involve[] a point of constitutional and/or federal law. Some examples include cases to which the United States is a party, cases involving Treaties, and cases involving ships on the high seas and navigable waterways (admiralty cases).” This excludes disputes based purely on state law but leaves plenty of cases for the court to decide.

With almost complete power to determine which appeals it will hear, the court prioritizes cases that could resolve important legal questions – for example, questions that have been decided in different ways by lower courts. Each U.S. court of appeals determines cases only within its circuit (regional grouping of states), and one circuit can resolve a legal dispute in a way that is at odds with the way another circuit has resolved it. This situation, called a “circuit split,” is one of the most common reasons the Supreme Court may decide to take a case – to resolve the split.

On the other hand, a case may not have resulted in a split but is of such importance that a definitive ruling by the Supreme Court would give important guidance to the lower courts.

Sometimes, a case may be taken not to resolve a recurring legal issue, but because fundamental fairness requires the court to step in and correct an injustice inherent in a lower court decision. An emergency appeal from an inmate on death row, for instance, might present this type of situation.

As a procedural matter, the justices decide which cases to take by reviewing the petitions for certiorari and then voting on which to review. The basic rule is that at least four justices must vote to hear the case. SCOTUSblog has a helpful summary of the specific procedure once the petition has been filed and the opposing party has been able to communicate with the court:

Seven of the current justices participate in the cert. pool, which is a labor-saving device in which a cert. petition is first reviewed by one law clerk in one of the seven chambers.  That clerk prepares a memorandum about the case that includes an initial recommendation as to whether the court should review the case; the memorandum is circulated to all seven chambers, where it is reviewed by the clerks and possibly the justices there. Justice Samuel Alito does not participate in the cert. pool. Instead, his law clerks review the incoming cert. petitions on their own and make recommendations directly to him.

Of course, with such a small proportion of cases receiving Supreme Court review, significant issues may not be immediately heard. Additionally, a case may raise an important issue, but for procedural or other reasons, it might make sense to wait for a different case that raises the same issue to grant review.

When the court declines to review a particular case, the lower court’s judgment stands. So the power to determine which cases to review is not only a way to preserve court resources, but also an important way to shape the law, signaling to other courts ways to address the same issue when it arises in other cases.