Mass. Gen. Laws ch. 211B § 6
The office of the chief justice 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 of the trial court shall be filled by appointment, from among the justices of the trial court departments, by a majority vote of the justices of the supreme judicial court. The chief justice of the trial court shall hold said office for a term of 5 years, and shall be eligible to be reappointed for additional 5-year terms. The chief justice of the trial court may be removed by a majority vote of the justices of the supreme judicial court. The chief justice of the trial court shall retain his commission as associate justice of the trial court, or of a predecessor court to which he was appointed, while serving as chief justice of the trial court, and may continue to perform such judicial duties as he may have exercised as associate justice, and such other responsibilities as otherwise provided by law.
Mass. Gen. Laws ch. 211B, § 6