Mass. Gen. Laws ch. 234A § 39
The court or the office of jury commissioner shall have authority to defer or advance any term of grand or trial juror service upon a finding of hardship, inconvenience, or public necessity provided the juror recognizes his firm obligation to perform juror service on the new date. The court shall have authority to excuse a grand juror from juror service, in part or in full, upon a finding of hardship, inconvenience, or public necessity, taking into consideration the length of grand juror service. The court shall have authority to excuse a trial juror from juror service, in part or in full, upon a finding of extreme hardship; the court shall exercise this authority strictly. Notwithstanding the fact that a juror has been summoned as a grand or trial juror, with or without right of postponement of service, the court shall have the discretionary authority to require the juror to serve either as a grand or trial juror, immediately or at a future date, at the original court location or at a different court location. The court may impose reasonable conditions and limitations, including appropriate time limitations, upon a term of juror service. It shall be the policy of this chapter that every trial juror shall be prepared to serve three trial days; the court shall not grant term limitations of less than three trial days except upon a finding that extreme hardship would be imposed upon the juror in the absence of such limitation. The court shall have the discretionary authority to dismiss a juror at any time in the best interests of justice. The court shall have authority to excuse and discharge an impanelled juror prior to jury deliberations after a hearing upon a finding of extreme hardship. The court shall have authority to excuse and discharge a juror participating in jury deliberations after a hearing only upon a finding of an emergency or other compelling reason. The court shall have authority to discharge an impanelled juror who has not appeared for juror service upon a finding that there is a strong likelihood that an unreasonable delay in the trial would occur if the court were to await the appearance of the juror. At any time during the trial, the court shall discharge any juror whose term limitation has expired upon the demand of the juror except where the court finds unusual circumstances; such discharge shall not be a ground for mistrial or objection by any party. The court may exercise any authority granted in this section at any time before or during a juror's term of service.
Mass. Gen. Laws ch. 234A, § 39