When Congress created the current three-tiered system of courts under Article III of the Constitution in 1896, United States Commissioners could be appointed by district judges to handle preliminary matters in criminal cases, like receiving bonds. In 1940, Congress expanded the duties of Commissioners to include trial of petty criminal offenses by consent. The Federal Magistrates Act of 1968 replaced the Commissioner with a position of Magistrate. In 1990, the title magistrate was changed to magistrate judge.

Magistrate judges are appointed by judges of the district court for a term of eight years. They may dispose of minor criminal offenses and may hold bench or jury trials in civil actions on consent of the parties. In addition, magistrate judges handle preliminary proceedings in felony matters, report and recommend to the district court on dispositive matters in civil cases, act as masters when appointed, and manage and rule on nondispositive matters in civil cases.