(a) Upon a day designated by the judge of the court, which shall be at least 20 days before the first day for which any of the panel then to be drawn is summoned, the clerk of such court shall repair to the office of the county clerk, and in the presence of a judge and of such county clerk, after the box containing the names has been well shaken by the county clerk, and being blindfolded shall, without partiality, draw from such box the names of a sufficient number of such persons, then residents of the county, not less than 30 for each 2 weeks that such court will probably be in session for the trial of common law cases, to constitute the petit jurors for the time being and where there is an additional judge in such court, a like number for each additional judge requiring a jury, unless the court shall otherwise order: Provided, that the clerk shall at any time, when directed by an order of the court draw in the manner above provided, such number of persons then residents of the county, as shall be required by the order to act as petit jurors in such court for such time as may be fixed in such order: And provided, that should the clerk draw from the box the name of a person who is known to be dead, to have been selected as a grand juror, a non-resident, absent from the State, unable to attend in consequence of illness, or that he is legally disqualified to serve as a juror, the clerk shall report the name of such person to the county clerk, and the clerk of such court shall draw other names until the required number have been selected: Provided, also that whenever there is pending for trial in any of the courts, any criminal cause wherein the defendant is charged with a felony, and the judge holding such court is convinced from the circumstances of the case that a jury cannot be obtained from the regular panel to try the cause, the judge may in his discretion, prior to the day fixed for the trial of the cause, direct the clerk to draw (in the same manner as the regular panel is drawn,) not exceeding 100 names as a special panel from which a jury may be selected to try the cause.(b) Notwithstanding the provisions of subsection (a), names of jurors may be randomly drawn by computer.