When the action is called for trial, a panel of potential jurors shall be selected at random from the citizens summoned for jury service who have appeared and have not been excused. A voir dire examination of the panel shall be conducted for the purpose of discovering any basis for challenge for cause and to permit the intelligent exercise of peremptory challenges. Any necessary additions to the panel shall be selected at random from the list of qualified jurors. The jury shall consist of six persons, unless the parties in their written demand for jury demand that the jury be twelve in number or consent to a less number. The parties may consent to a jury less than six in number but not less than three, and such consent shall be entered in the record.