Final answer:
At least four of the nine U.S. Supreme Court justices must agree to grant a writ of certiorari for a case to be accepted and placed on the docket, a protocol known as the Rule of Four.
Step-by-step explanation:
The U.S. Supreme Court selects only a small fraction of cases for review out of the thousands of petitions it receives annually. For a case to be placed on the docket, at least four of the nine Justices must vote to grant a writ of certiorari. This is known as the Rule of Four. The Court typically follows this practice to ensure that there is a significant interest among the Justices in the legal questions presented by the case.
Once a writ of certiorari has been granted, the case is scheduled on the Court's docket, and the justices will then hear arguments, review the records from the lower courts, and eventually render a decision. The number of justices has been set at nine since 1869, comprising one chief justice and eight associate justices, all serving lifetime appointments following nomination and confirmation processes.