(a) Each judge of a district court of Dallas County that gives preference to criminal cases, each judge of a criminal district court of Dallas County, and each judge of a county criminal court of Dallas County, with the consent and approval of the Commissioners Court of Dallas County, may appoint a magistrate to perform the duties authorized by this subchapter.
(b) Judges may authorize one or more magistrates to share service with more than one court.

(c) If a magistrate serves more than one court, the magistrate’s appointment must be made with the unanimous approval of all the judges under whom the magistrate serves.