How have the courts treated the evidence in a mail fraud trial in which every fact relevant to the issue was visually and graphically developed?

Rarely has any mail fraud case been tried in which every fact relevant to the issue has been so visually and graphically developed as in this case. The jury heard and saw the witnesses for almost two months. The critical area to be explored must be the court's charge. Was the jury properly instructed? The individual defendants here convicted were business men of many years' standing with no previous criminal records. They should not be made the victims of a few disgruntled purchasers who well may have been manually inept or of a co-defendant obviously anxious to save himself. On the other hand an appellate court "should not attempt to usurp the function of the jury" (Stearn v. United States, 4 Cir., 1927, 18 F.2d 465, 468) and in a mail fraud case the court must be mindful of the fact that "It is only necessary to prove that it is a scheme reasonably calculated to deceive persons of ordinary prudence and comprehension, * * *" (Silverman v. United States, 5 Cir., 1954, 213 F.2d 405, 407).