In the case of Harris, Alias Smith, and Green v. United States in 1912, the defendants were charged with conspiracy to defraud the U.S. government by using mail for fraudulent purposes. The Supreme Court ruled against them on two main grounds: firstly that a conspiracy was formed even if its members did not know each other personally; secondly that it is illegal to use mail for fraudulent schemes regardless of whether or not they are successful. This ruling expanded federal jurisdiction over fraud cases involving mails and established legal precedents regarding conspiracies.

In the dissenting opinion for Harris, Alias Smith, and Green v. United States (1912), Justice Hughes argued that the defendants' constitutional rights were violated because they did not have an opportunity to cross-examine a key witness against them. The case involved charges of conspiracy to defraud the government by using counterfeit money orders. A crucial piece of evidence was a letter written by one defendant implicating all others in the scheme. This letter was read aloud in court but its author had died before trial and therefore could not be cross-examined about it as required under Sixth Amendment's Confrontation Clause which guarantees criminal defendants right to confront witnesses against them. Justice Hughes believed this denial constituted reversible error since it deprived defendants of their constitutional right to challenge credibility or reliability of testimonial evidence presented against them.