Mass. Gen. Laws ch. 211B § 5
The office of the chief justice of a department of the trial court, as provided in section 1, shall not be deemed a judicial office as comprehended under the provisions of Article I of Chapter III of Part the Second of the Constitution. Said office of chief justice shall be filled by appointment, from among the justices appointed to the particular department, by the chief justice of the trial court. A chief justice shall hold said office for a term of 5 years, and shall be eligible to be reappointed for additional 5-year terms. A chief justice, so appointed, may be removed from that office prior to the expiration of his term by the chief justice of the trial court; provided, however, that any such removal is not for arbitrary or capricious reasons and, if the employee so requests, is approved by the Committee.
Mass. Gen. Laws ch. 211B, § 5