Section 640 — Criminal Code: Determination of challenge for cause

If a challenge is made on a ground mentioned in section 638, the judge shall determine whether the alleged ground is true or not and, if the judge is satisfied that it is true, the juror shall not be sworn. On the application of the accused or prosecutor or on the judge’s own motion, the judge may order the exclusion of all jurors, sworn and unsworn, from the court room until it is determined whether the ground of challenge is true if the judge is of the opinion that the order is necessary to preserve the impartiality of the jurors.