In the United States v. Strang et al., 1920, the Supreme Court dealt with a case involving fraudulent use of mails and conspiracy to defraud. The defendants, Strang and others, were charged with using mail for fraudulent purposes by promoting an investment scheme that was not legitimate. They argued that they had no intent to defraud as they believed in their business's success despite its failure eventually. However, the court ruled against them stating that even if there was a genuine belief in future success on part of the defendants, it did not justify or excuse false representations made at present about past or existing facts which were used to deceive investors into investing money into their venture. Therefore, regardless of their intentions or beliefs about future profitability of their enterprise, making false statements through mails constituted fraud under federal law.

The dissenting opinion in the United States v. Strang et al., 1920 case was not explicitly stated, as it is often the case with older court decisions where only majority opinions were recorded and published. Therefore, a summary of a dissenting opinion for this particular Supreme Court Case cannot be provided due to lack of available information.