The magistrate judge's seat is not a separate court; the authority that a magistrate judge exercises is the jurisdiction of the district court itself, delegated to the magistrate judge by the district judges of the court under governing statutory authority, local rules of court, or court orders. Rather than fixing the duties of magistrate judges nationwide, the Federal Magistrates Act allows each district court to assign duties to the magistrate judges as fits the needs of that court.
In criminal proceedings, magistrate judges preside over misdemeanor and petty offense cases, and as to all criminal cases (felony and misdemeanor) may issue search warrants, arrest warrants, and summonses, accept criminal complaints, conduct initial appearance proceedings and detention hearings, set bail or other conditions of release or detention, hold preliminary hearings and examinations, administer oaths, conduct extradition proceedings, and conduct evidentiary hearings on motions to suppress evidence in felony cases for issuance of reports and recommendations to the district judge.
The Supreme Court has held in Peretz v. United States that magistrate judges may supervise the jury selection in a felony trial unless a party objects.
In civil proceedings, magistrate judges typically manage discovery and other pretrial matters. They are authorized to issue orders in pretrial matters as long as the order is not dispositive of the case as a whole (for example, an order granting summary judgment is not within purview). They may also be assigned to write reports and recommendations to the district judge as to dispositive matters. With the consent of the parties, they may adjudicate civil cases in the same manner as a district judge, including presiding over jury or non-jury trials.
