If it is shown, on motion of the defendant, that the defendant has been prejudiced in his defense on the merits by the defect, imperfection, omission, uncertainty, or variance, with respect to which an amendment is made, the court shall grant a continuance for a reasonable time. In determining whether the defendant has been prejudiced in his defense upon the merits, the court shall consider all the circumstances of the case and the entire course of the prosecution. If it becomes necessary to discharge the original jury from further consideration of the case, the trial before a new jury will not constitute double jeopardy.