It shall be sufficient cause of challenge of a petit juror that he lacks any one of the qualifications mentioned in Section 2 of this Act; or if he is not one of the regular panel, that he has served as a juror on the trial of a cause in any court in the county within one year previous to the time of his being offered as a juror; or that he is a party to a suit pending for trial in that court. It shall be the duty of the court to discharge from the panel all jurors who do not possess the qualifications provided in this Act, as soon as the fact is discovered. If a person has served on a jury in a court within one year, he shall be exempt from again serving during such year, unless he waives such exemption. It shall not be a cause of challenge that a juror has read in the newspapers an account of the commission of the crime with which the prisoner is charged, if such juror shall state on oath that he believes he can render an impartial verdict according to the law and the evidence. In the trial of any criminal cause, the fact that a person called as a juror has formed an opinion or impression, based upon rumor or upon newspaper statements (about the truth of which he has expressed no opinion,) shall not disqualify him to serve as a juror in such case, if he shall upon oath state that he believes he can fairly and impartially render a verdict therein, in accordance with the law and the evidence, and the court shall be satisfied of the truth of such statement.