Prior to or during any term of court at which a jury may be necessary, the clerk or deputy clerk, in the presence of the judge or, in his absence, a commissioner in chancery appointed for the purpose by the judge, shall, after thoroughly mixing the ballots in the box, openly draw therefrom such number of ballots as are necessary for the trial of all cases during the term or as the judge shall direct. However, a commissioner shall not be eligible to witness the drawing of a jury to be used in the trial of any case in which he will be interested as attorney or otherwise.