S.C. Code § 14-7-1340
Such alternate jurors shall sit near the jury panel charged with the case, shall have the same opportunities for seeing and hearing the proceedings in the case, and shall take the same oath as the jurors already sworn and shall attend at all times the trial of the cause in company with the other jurors. They shall obey the orders of, and be bound by, the admonition of the court upon each adjournment of the court and, if the regular jurors are ordered to be kept in custody by the court during the trial of the cause, such alternate jurors shall also be kept in confinement with the other jurors and, except as hereinafter provided, shall be discharged upon the final submission of the case to the jury. If, before the final submission of the case to the jury, a juror thereon dies or becomes so ill or disabled as to be unable in the judgment of the court to perform his duties thereon, the court shall order him to be discharged and draw the name of one of the alternates, if there be more than one, by ballot to serve in the place of such dead or discharged juror throughout the remainder of the proceedings, being subject to the same rules and regulations as applied to the remainder of jurors, just as though he had been one of the original jurors. If there be but one alternate, he shall be placed upon the jury panel for all further proceedings in such cause.
S.C. Code § 14-7-1340