(a) For the purposes described by this chapter, the court may order any defendant to submit to examination, including a defendant who is free on bail. If the defendant fails or refuses to submit to examination, the court may order the defendant to custody for examination for a reasonable period not to exceed 21 days. Custody ordered by the court under this subsection may include custody at a facility operated by the commission.
(b) If a defendant who has been ordered to a facility operated by the commission for examination remains in the facility for a period that exceeds 21 days, the head of that facility shall cause the defendant to be immediately transported to the committing court and placed in the custody of the sheriff of the county in which the committing court is located. That county shall reimburse the facility for the mileage and per diem expenses of the personnel required to transport the defendant, calculated in accordance with the state travel rules in effect at that time.

(c) The court may not order a defendant to a facility operated by the commission for examination without the consent of the head of that facility.