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Why does the Supreme Court not hear witnesses or receive new evidence during oral arguments?

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A person ascends the steps of the west facade of the United States Supreme Court Building in Washington, D.C., with its tall columns and a round fountain in the foreground. — Supreme Court of the United States The west facade of the U.S. Supreme Court building, Washington, D.C.

The Supreme Court of the United States does not hear witnesses or receive new evidence during oral arguments because it functions primarily as an appellate body rather than a trial court.12

As the country’s court of last resort, the Supreme Court’s role is to review the decisions of lower courts to ensure justice and to establish binding rules of decision that provide uniformity across the judicial system. Because the factual record of a case is established during the initial trial, the Supreme Court focuses its proceedings on legal and constitutional interpretation rather than the re-examination of facts or testimony.32

Once the Court grants a certiorari request to hear a case, it relies on the existing lower-court records and briefs submitted by the parties. During oral arguments, the justices hear from the petitioners and respondents, who are allotted time to persuade the Court on how the Constitution should be interpreted regarding the legal issues at hand.2