New York Consolidated Laws, Criminal Procedure Law - CPL § 270.30 Trial jury;  alternate jurors

1. Immediately after the last trial juror is sworn, the court may in its discretion direct the selection of one or more, but not more than six additional jurors to be known as “alternate jurors”, except that, in a prosecution under section 125.27 of the penal law, the court may, in its discretion, direct the selection of as many alternate jurors as the court determines to be appropriate.  Alternate jurors must be drawn in the same manner, must have the same qualifications, must be subject to the same examination and challenges for cause and must take the same oath as the regular jurors.  After the jury has retired to deliberate, the court must either (1) with the consent of the defendant and the people, discharge the alternate jurors or (2) direct the alternate jurors not to discuss the case and must further direct that they be kept separate and apart from the regular jurors.

2. In any prosecution in which the people seek a sentence of death, the court shall not discharge the alternate jurors when the jury retires to deliberate upon its verdict and the alternate jurors, in the discretion of the court, may be continuously kept together under the supervision of an appropriate public servant or servants until such time as the jury returns its verdict.  If the jury returns a verdict of guilty to a charge for which the death penalty may be imposed, the alternate jurors shall not be discharged and shall remain available for service during any separate sentencing proceeding which may be conducted pursuant to section 400.27.