In the 1944 case Kann v. United States, the Supreme Court ruled on a matter concerning double jeopardy and mail fraud. The defendants were charged with two counts of mail fraud: one for devising a scheme to defraud and another for causing an envelope to be delivered by mail as part of that scheme. They were convicted on both counts but argued that this constituted double jeopardy because they had been tried twice for essentially the same offense. The Supreme Court agreed, ruling in favor of Kann and his co-defendants. It held that where mailing is merely incidental to an essential element of the scheme or its success, it cannot be made into separate offenses under each count; hence convicting them separately would violate their protection against double jeopardy.

In the dissenting opinion for Kann v. United States, Justice Frank Murphy argued that the majority's decision was a misinterpretation of the law and an overreach of federal power. He contended that there was no evidence to suggest that Kann had intended to defraud or deceive anyone when he transferred his assets prior to filing bankruptcy. Furthermore, he disagreed with the majority's assertion that such transfers were inherently fraudulent under Section 29(b) of Bankruptcy Act, arguing instead this section should be interpreted narrowly as only applying in cases where fraud is explicitly proven. In essence, Murphy believed it was not enough for someone merely to transfer their assets before declaring bankruptcy; they must also have done so with fraudulent intent which according to him wasn't established in this case.