Massachusetts General Laws Part III. Courts, Judicial Officers and Proceedings in Civil Cases (Ch. 211-262) Ch. 258, § 6

The public attorney shall defend all civil actions brought against a public employer or public employee of the commonwealth pursuant to this chapter. Service of process for such civil action shall be made upon the public attorney or, where no such public attorney has been employed for such purpose at the time service is made, service shall be made upon the executive officer of such public employer.