Mich. Comp. Laws § 767.11: Grand jury; size; foreman, appointment.

Sec. 11.

There shall be no more than 17 persons nor less than 13 persons sworn on any grand jury; and after such jurors have been impaneled and have received their charge from the court, they shall retire with the officer appointed to attend them and before they proceed to discharge the duties of their office, the court shall appoint 1 of their number to be foreman and the clerk shall record the same.