Massachusetts General Laws Part IV. Crimes, Punishments and Proceedings in Criminal Cases (Ch. 263-280) Ch. 277, § 70B

Except as otherwise provided by law, a criminal case shall not be placed on file, on motion of a district attorney or assistant district attorney, unless such motion is accompanied by a written statement of the reasons for such disposition, signed by the district attorney or assistant district attorney, which shall be filed with the pleadings, and also accompanied by a statement of any previous criminal record of the accused.