At any time after rendition of a verdict of guilty and before sentence, the court may, upon motion of the defendant, set aside or modify the verdict or any part thereof upon the following grounds: 1. Any ground appearing in the record which, if raised upon an appeal from a prospective judgment of conviction, would require a reversal or modification of the judgment as a matter of law by an appellate court. 2. That during the trial there occurred, out of the presence of the court, improper conduct by a juror, or improper conduct by another person in relation to a juror, which may have affected a substantial right of the defendant and which was not known to the defendant prior to the rendition of the verdict; or 3. That new evidence has been discovered since the trial which could not have been produced by the defendant at the trial even with due diligence on his part and which is of such character as to create a probability that had such evidence been received at the trial the verdict would have been more favorable to the defendant.