Mass. Gen. Laws ch. 279 § 65
There shall be present at the execution of the sentence of death, in addition to the superintendent, deputy and such officers of the state prison as the superintendent deems necessary, the commissioner of correction or his representative, the person performing the execution under the direction of the superintendent, if any, and the following physicians: the prison physician, the state surgeon, and a medical examiner for Norfolk county, or if any or all are unable to be present, such physicians as the superintendent approves. The physicians present shall be the legal witnesses of the execution. There may also be present, upon the request of the prisoner who is to be executed, the immediate members of the family of the prisoner. There may also be present, upon the request of said prisoner, a priest, minister, or other representative of religion. There may also be present the sheriff of the county where the prisoner was convicted, or his deputy, and, with the approval of the superintendent, not more than three other persons.
Mass. Gen. Laws ch. 279, § 65