Which type of court is primarily responsible for trial cases in the federal system?

The United States District Courts are the primary trial courts in the federal judicial system, which is why this answer is correct. These courts have jurisdiction over a wide range of federal cases, including civil lawsuits, federal crimes, and matters involving federal laws, treaties, or constitutional issues. Each district court serves a specific geographic area, and there are multiple districts across the country.

In contrast, state courts handle the majority of legal disputes and are not part of the federal system. Municipal courts generally address violations of local ordinances and handle lesser offenses, while Courts of Appeals, as appellate courts, do not conduct trials but instead review decisions made by trial courts for legal errors. Therefore, the structure and specific role of the United States District Courts clearly designate them as the trial courts of the federal system.