Maryland Code, Criminal Procedure § 4-103

(b)(1) If a defendant is charged with a felony other than a felony within the jurisdiction of the District Court, the defendant may request a preliminary hearing at the defendant's initial appearance or at any time within 10 days after the initial appearance.

(2) If the defendant does not request a preliminary hearing within 10 days after the initial appearance, the right to a preliminary hearing is waived.

(c)(1) If a defendant is charged with a felony other than a felony within the jurisdiction of the District Court, the right of a defendant to a preliminary hearing is absolute if:

(2) If the defendant is charged by grand jury indictment, the right of a defendant to a preliminary hearing is not absolute but the court may allow the defendant to have a preliminary hearing.

(3) In any other case, the right of a defendant to a preliminary hearing is not absolute, but on motion of the State's Attorney or the defendant, and subject to the Maryland Rules, the court may allow the defendant to have a preliminary hearing.