Mass. Gen. Laws ch. 32 § 65H
A chief justice, administrative justice, justice, associate justice, judge, associate judge, or special justice, hereafter in this section and in section sixty-five I called judge, who has paid the full amount of the contributions required, if any, by paragraph (b) of section sixty-five D, shall receive a retirement allowance, at the option of the judge and in lieu of any pension or retirement allowance to which he may be entitled, if any, under section sixty-five A, sixty-five B, or sixty-five D, to become effective on the date of his retirement. Payments under such retirement allowance shall be made as provided in sections twelve and thirteen. The yearly amount of such retirement allowance to a judge provided for under this section shall, subject to the limitations set forth in this section, be based on the salary of the judge at the time of his retirement, multiplied by the number of continuous years of service as a judge, and further multiplied by the percent allowable based on the age at the date of retirement as shown in the following table:
The amount of the retirement allowance provided for in this section shall not exceed seventy-five percent of the salary of the judge at the time of his retirement. No such retirement allowance shall be paid unless the judge shall have served continuously as a judge for at least ten years. For the purpose of this section, a year of service as a special justice shall be computed by dividing the number of days of actual sittings in such capacity by two hundred and sixty, whether or not such sittings occurred in one calendar or fiscal year. A judge shall be deemed to have served continuously even though a period not in excess of thirty days shall have intervened between the holding of one judicial office and the holding of another judicial office.
Mass. Gen. Laws ch. 32, § 65H