If the jury persist in finding an informal verdict, from which, however, it can be clearly understood that their intention is to find in favor of the defendant upon the issue, it must be entered in the terms in which it is found, and the court must give judgment of acquittal. But no judgment of conviction can be given unless the jury expressly find against the defendant, upon the issue, or judgment be given against him on a special verdict.
R.L.1910, § 5927.