The U.S. Supreme Court generally only hears the cases that it wants to hear. Parties that lose a case in a federal court of appeals or state high court can ask the U.S. Supreme Court to hear their case by filing a petition for a writ of certiorari. If four justices agree to hear a case, then the writ of certiorari will be granted. But this happens relatively rarely. Of the thousands of petitions for certiorari filed each year, the Supreme Court only hears between 70 and 80. Though the Court has never fully explained why it chooses the cases it does, it has offered some guidance through Supreme Court Rule 10. After explaining that granting a writ of certiorari is discretionary, Rule 10 offers the following examples of the sorts of cases the Supreme Court is likely to accept.

The first two examples are found in subsections (a) and (b) of Rule 10. Theyre largely the same, since they involve two lower courts reaching different conclusions on an important federal question. The two courts might be two different federal courts of appeals, two state high courts, or a federal court of appeals and a state high court. In such circumstances, the Supreme Court may decide to accept a case that allows it to resolve the split in lower-court authority. The only difference between these examples is that Rule 10(a) also lists correcting a federal court of appeals departure from the accepted and usual course of judicial proceedings as a reason for granting certiorari, but Rule 10(b) has no similar statement.

The third example, found in Rule 10(c), is where a state court or federal court of appeals decides an important federal question that the Supreme Court has never addressed, but the justices believe it should be. Alternatively, a federal court of appeals or state court might have decided such a question contrary to Supreme Court precedent. In either case, the Supreme Court might step in to correct the lower court. This does not happen very often.

Rule 10 explains that these examples arent meant as limits on the Supreme Courts discretion in deciding to hear a case. For example, just because a lower, local court ignores Supreme Court precedent in reaching its own decision doesnt guarantee the Supreme Court will review that decision. But the guidance contained in Rule 10 still provides some insight into an otherwise-obscure process.