Mass. Gen. Laws ch. 22C § 59
The colonel may, upon petition of the commissioner of mental health or the commissioner of developmental services, appoint as special state police officers employees of the department of mental health or the department of developmental services or employees of various institutions under the respective jurisdictions of said departments, who shall have the same power to make arrests as the state police for any criminal offense committed in or upon lands or structures within the charge of said departments or of the various institutions under the respective jurisdictions of said departments. Such special state police officers shall be sworn before a justice of the peace or notary public who shall make return thereof to the department upon a form provided by said department. Upon receipt of said return the department shall issue a license to each person designated to act as a special state police officer, and such license shall, in any court of the commonwealth, be competent evidence of the validity of the appointment of the person named therein and of his authority to act as such special state police officer. A special state police officer shall hold his office until his license expires or is revoked by the colonel, or until the petitioner files a notice with the department that the services of such officer are no longer required. The colonel may provide that the license and any renewal thereof shall expire on the anniversary of the birth of the person named therein not less than one nor more than two years following the date of issue. They shall report to the colonel as to their official acts at such times and in such manner as he may require. They shall serve without pay, except for their regular compensation as employees of the department of mental health, the department of developmental services, or the various institutions under the respective jurisdictions of said departments, and they shall receive no fees for services for return of any criminal process.
Mass. Gen. Laws ch. 22C, § 59