Mont. Code Ann. § 25-7-304

If, after the impaneling of the jury and before verdict, a juror becomes sick and is unable to perform the juror's duty, the court may order the juror to be discharged. In that case, subject to the provisions of Rule 47(c), M.R.Civ.P., the trial may proceed with the other jurors or another juror may be sworn and the trial may begin anew or the jury may be discharged and a new jury impaneled.