When the offense is divided into degrees or necessarily includes lesser offenses and the court, on a motion for new trial, is of the opinion that the evidence does not sustain the verdict but is sufficient to sustain a finding of guilt of a lesser degree or of a lesser offense necessarily included in the one charged, the court shall not grant a new trial but shall find or adjudge the defendant guilty of the lesser degree or lesser offense necessarily included in the charge, unless a new trial is granted by reason of some other prejudicial error.