Massachusetts General Laws Part I. Administration of the Government (Ch. 1-182) Ch. 12, § 21

The superintendent of police of Boston shall, upon the written request of the district attorney for the Suffolk district, detail for police and detective service under his direction inspectors or police officers, not exceeding two in number. Such inspectors or officers shall receive no extra compensation for services thus rendered, and shall be subject to the rules and regulations of the police department, unless relieved therefrom temporarily by said superintendent or by the police commissioner of Boston.