Two kinds of challenges are allowed in selecting the jury, challenges for cause, and peremptory challenges. A challenge for cause is exercised when the examination of a juror discloses some disqualification rendering him incompetent to try the accused. A peremptory challenge is one allowed by law without assigning any reason, nor can any reason be required. This right can be exercised according to the judgment, will or caprice of the party entitled thereto.16

5 15 Borrilli vs. People, 164 Ill., 559.

When a juror upon his examination proves unsatisfactory to a party, he may be excused by the exercise of a peremptory challenge, if his examination fails to disclose ground to challenge for cause. No matter how well qualified a juror may be, he may be excluded from the jury by peremptory challenge. And it is error for the court to refuse to allow a peremptory challenge after overruling a challenge for cause.17