(1) When the law requires that a grand jury be empaneled or when ordered by the judge or judges, the jury commissioner shall draw grand jurors pursuant to this section.

(2) The jury commissioner shall draw by chance forty names, or such other number as directed by the judge or judges, of persons the jury commissioner has investigated and determined to be qualified pursuant to section 25-1668. The jury commissioner shall then prepare a list of such names. Such list shall also contain the place of residence and occupation of each person on the list.

(3) The jury commissioner shall notify or summon persons selected under subsection (2) of this section as directed by the judge or judges.

(4) The list of names drawn pursuant to subsection (2) of this section shall then be turned over by the jury commissioner to a board to consist of the jury commissioner, the presiding judge of the district court, and one other person whom the presiding judge shall designate. The presiding judge shall be the chairperson. Such board shall select from such list the names of sixteen persons to serve as grand jurors and the names of three additional persons to serve as alternate jurors.

(5) The alternate jurors shall sit with the grand jury and participate in all investigative proceedings to the same extent as the regular grand jurors. Alternate grand jurors shall be permitted to question witnesses, review evidence, and participate in all discussions of the grand jury which occur prior to the conclusion of presentation of evidence. When the grand jury has determined that no additional evidence is necessary for its investigation, the alternate grand jurors shall be separated from the regular grand jurors and shall not participate in any further discussions, deliberations, or voting of the grand jury unless one or more of the regular grand jurors is or are excused because of illness or other sufficient reason. Such alternate jurors shall fill vacancies in the order of their selection.