Massachusetts General Laws Part IV. Crimes, Punishments and Proceedings in Criminal Cases (Ch. 263-280) Ch. 276, § 90

A probation officer shall not be an active member of the regular police force, but so far as necessary in the performance of his official duties shall, except as otherwise provided, have all the powers of a police officer, and if appointed by the superior court may, by its direction, act in any part of the commonwealth. He shall report to the court, and his records may at all times be inspected by police officials of the towns of the commonwealth; provided, that his records in cases arising under sections fifty-two to fifty-nine, inclusive, of chapter one hundred and nineteen shall not be open to inspection without the consent of a justice of his court.