Wyo. Stat. § 7-5-103: Composition; qualifications; alternates.

(a) A grand jury shall consist of twelve (12) persons who shall possess the qualifications of trial jurors as provided by W.S. 1-11-101.

(b) The district judge may direct the selection of one (1) or more alternate jurors who shall sit as regular jurors before an indictment is found. If a member of the grand jury becomes unable or disqualified to perform his duty he shall be replaced by an alternate juror.