If a person is committed to the secretary as criminally insane, commitment and treatment must not exceed the maximum possible sentence for any offense charged. Therefore:

(1) The administration, with the assistance of the office of the attorney general where necessary must determine at the time of commitment the maximum possible sentence for any offense charged, and thereby compute a maximum release date for every individual so committed.

(2) If the committed person has not been released by court order six months prior to the expiration of the maximum possible release date, the administration, must notify the committing court and prosecuting attorney of its computation of maximum release date and the requirement that the person must be released on that date unless civil proceedings are instituted or the court determines that the computation of maximum release date is incorrect.