Mass. Gen. Laws ch. 234A § 30
The office of jury commissioner or the court may impose a standby status condition on any trial or grand juror before or during his term of service. A juror on whom such condition has been imposed shall be referred to as a standby juror. The standby juror shall be prepared to serve on each day of his term or service, but he shall not appear for service unless directed to do so in the following manner. The standby juror shall make telephone inquiry to a designated office or court after three o'clock in the afternoon on the court day preceding his term of service in order to obtain specific instructions as to whether or not he should appear for juror service on the following court day. A juror may be continued on standby status from day to day, but his term of service shall not be enlarged because of the standby condition unless the juror has been impanelled on a case or unless ordered by the court. The designated office or court may use an automatic telephone answering device for the purpose of giving instructions to and receiving messages from standby jurors. A notice of standby status may be enclosed with the juror summons or may be sent separately. Any other form of standby notice reasonably contemplated to give actual notice may be used. The court shall have discretionary authority to excuse a juror from the standby condition upon a showing of unusual hardship caused by the condition, but such juror shall serve or be available to serve without the standby condition unless further excused by the court. The office of jury commissioner or the court may order a standby juror to serve or to appear for service upon a date and time certain without the necessity of telephone inquiry by the standby juror. The office of jury commissioner or the court may make further modifications of the standby condition as are reasonably contemplated to facilitate the management of cases before the court.
Mass. Gen. Laws ch. 234A, § 30