If, when all is said and done, a conviction is sure that an error did not influence a jury, or had but very slight effect, a verdict and a judgment should stand, except perhaps where the departure is from a constitutional norm or a specific command of Congress. But if one cannot say, with fair assurance, after pondering all that happened without stripping an erroneous action from the whole, that a judgment was not substantially swayed by an error, it is impossible to conclude that substantial rights were not affected.
Petitioners sought review of a judgment that convicted them of a single count of general conspiracy in violation of 18 U.S.C.S. § 88, asserting that they suffered substantial prejudice by being convicted with evidence that the United States admitted proved eight or more different conspiracies that were executed through a common key figure. The United States asserted that the variance in proof from the single conspiracy charged in the indictment was harmless error under 28 U.S.C.S. § 391.
Did the error in admitting evidence affect the petitioners’ substantial right?
The Court held that the error affected petitioners' substantial right to not be tried en masse for the conglomeration of distinct and separate offenses committed by others. Accordingly, the judgment of conviction was reversed, and the case was remanded for further proceedings.