Juries Act 1962

(1) The Court in which a criminal trial is to be held may direct that, in addition to the 12 persons required under section 37(1) to be the jury to try the issues on that trial, not more than 3 jurors summoned in accordance with section 30 shall be chosen and returned as reserve jurors in respect of that trial.

(c) shall be subject to the same challenges and liability to be stood by and to be discharged;

as a juror, and for that purpose the law in respect of jurors shall apply to and in relation to a reserve juror with such modifications as are required by this section.

(3) A juror at a criminal trial who, prior to the time the jury retires to consider its verdict, dies or becomes disqualified from or is discharged from performing his duties as a juror shall be replaced by a reserve juror, if any, who, if there is more than one reserve juror available at that trial, shall then be determined by lot in such manner as the Court determines.

(4) Where a reserve juror who has not replaced a juror dies or becomes disqualified from or discharged from performing his duties as a juror, the trial in respect of which he is a reserve juror shall not be affected by that death, disqualification or discharge.

(5) Immediately before the jury retires to consider its verdict, a reserve juror who has not replaced a juror shall be discharged.