Any replacement juror called is subject to examination, challenge for cause, and peremptory challenge as any other unaccepted juror.
The judge may reconsider his denial of the challenge for cause, reconsidering facts and arguments previously adduced or taking cognizance of additional facts and arguments presented. If upon reconsideration the judge determines that the juror should have been excused for cause, he must allow the party an additional peremptory challenge.
N.C. Gen. Stat. § 15A-1214