Which body is composed of nine judges/justices and is crucial to interpreting the Constitution?

The body that is composed of nine judges or justices and plays a vital role in interpreting the Constitution is the Supreme Court. This court is the highest judicial authority in the United States and has the ultimate power to make decisions on cases that involve constitutional issues. Its interpretations can set precedents that influence future laws and governmental actions. The Supreme Court's decisions can uphold or invalidate laws and executive actions, ensuring that they align with the Constitution. This function is fundamental to maintaining the rule of law and protecting individual rights within the framework of the Constitution.

While the Federal Court System includes the Supreme Court, it also encompasses lower courts that handle a variety of cases, but the Supreme Court is notably the final arbiter of constitutional questions. Congress, as the legislative body, is responsible for making laws, and the Executive Branch carries out those laws; neither of these bodies interprets the Constitution in the same direct manner as the Supreme Court does.