When a person charged with a criminal offense, who has not waived his right to trial by jury, is put upon his trial, the clerk, under the direction of the court, shall place the names of all the traverse jurors summoned and in attendance in a box upon separate tickets, and the names, after being mixed, shall be drawn from the box by the clerk, one at a time. The Supreme Judicial Court shall by rule provide the manner of exercising all challenges, and the number and order of peremptory challenges. [PL 1965, c. 482, §1 (AMD).]

Whenever by reason of the prospective length of a criminal trial the court in its discretion shall deem it advisable, it may direct that jurors in addition to the regular panel be called and impanelled to sit as alternate jurors. Such alternate jurors in the order in which they are called shall replace jurors who, prior to the time the jury retires to consider its verdict, become unable or disqualified to perform their duties. Such alternate jurors shall be drawn in the same manner, shall have the same qualifications, shall be subject to the same examination and challenges, shall take the same oath and shall have the same functions, powers, facilities and privileges and be subject to the same obligations and penalties as jurors on the regular panel. An alternate juror who does not replace a juror on the regular panel shall be discharged when the jury retires to consider its verdict. The Supreme Judicial Court shall by rule provide the number of alternate jurors, the manner of exercising all challenges to alternate jurors, and the order and number of peremptory challenges to alternate jurors. [PL 1965, c. 356, §47 (RPR).]