Mass. Gen. Laws ch. 221, § 72: Tenure

Section 72. Officers appointed as court officers to attend upon the sessions of the supreme judicial, appeals or superior court in any county, including chief deputies, assistant chief deputies and all chief court officers designated under section seventy-one, shall hold office during good behavior and until they are removed by the court administrator or, with respect to court officers of the supreme judicial court and the appeals court, their respective chief justices, for cause.