Massachusetts General Laws Part I. Administration of the Government (Ch. 1-182) Ch. 18A, § 3

The commissioner shall appoint, with the approval of the secretary of health and human services, a deputy commissioner who shall not be subject to the provisions of chapter thirty-one and to whom the provisions of section nine A of chapter thirty shall not apply, but who shall possess the same qualifications required of the commissioner, except that he shall have had not less than five years of experience in work related to juvenile delinquency, of which at least two shall have been as an administrator. Said deputy commissioner shall serve at the pleasure of the commissioner, and shall devote his full time during business hours to the duties of his office. He shall exercise such authority and discharge such duties of the commissioner as the commissioner may from time to time delegate to him and, in the absence or incapacity of the commissioner, or in the event of a vacancy in the office of commissioner, shall act as the commissioner until the absence or incapacity shall have terminated or the vacancy shall have been filled.