N.H. Rev. Stat. Ann. § 622:51

The superior court may at any time, with notice to the attorney general and to the county attorney, if any, who prosecuted the case, upon application and after a hearing, for due cause shown, investigate the question whether there is sufficient reason for the detention in the unit of any person who has been committed thereto by criminal proceedings, and may order his discharge, when such order ought to be made, without the formality of a writ.