Mass. Gen. Laws ch. 262 § 53B
Any uniformed member of the department of state police, appointed under section ten of chapter twenty-two C, on duty at night, or on vacation or furlough, or on a day off, who attends as a witness in a civil or criminal suit pending in a district court or in a juvenile court or in the superior court shall be allowed a witness fee in the amount of three dollars for each day's attendance including his first day's attendance as arresting officer. Any such officer who attends court held at a place other than his residence in a criminal case pending in any court of the commonwealth shall be reimbursed in accordance with the mileage rate then in effect for state employees as set by the commissioner of administration for travel out and home for each day's attendance, except that travel allowance shall not be allowed when such travel is made in state-owned vehicles. Each officer shall certify in writing under the penalties of perjury the amount of his travel and attendance. Such payments shall be in addition to his other expenses necessarily and actually incurred as provided for in section fifty and shall be paid in the same manner.
Mass. Gen. Laws ch. 262, § 53B