Rule 18.08 - Tenure and ExcusalSubd. 1.Tenure. A grand jury must be drawn for a specified period of service, not to exceed 12 months, as designated by court order. The grand jury must not be discharged, and its powers must continue until the latest of the following: (a) the period of service is completed;(b) its successor is drawn; or(c) it has completed an investigation, already begun, of a particular offense.Subd. 2.Excusal. For cause shown, the court may excuse a juror temporarily or permanently. The court may impanel another person in place of the excused juror.