In Boyd v. United States, 116 U.S. 616 (1886) the government initiated a civil forfeiture proceeding against two New York businessmen who illegally imported thirty-five cases of plate glass. The defendants there claimed on appeal that the government's demand for invoices violated the Search and Seizure Clause of the Fourth Amendment and the Self-Incrimination Clause of the Fifth Amendment. Noting the relationship between the two amendments, the Court found that the compulsory production of these private papers violated the Constitution and, as a result, the evidence could not be used against the defendants at trial. Id. at 630, 634-35. Importantly, the Court did not rely upon the Fourth Amendment alone for the exclusion principle it announced. Rather, it was the intersection between the Fourth and Fifth Amendments that required exclusion. The United States Supreme Court held unconstitutional, under the Fourth and Fifth Amendments, a subpoena duces tecum ordering Boyd to produce an invoice which established his guilt for nonpayment of a duty tax. The Court explained that it was "unable to perceive that the seizure of a man's private books and papers to be used in evidence against him is substantially different from compelling him to be a witness against himself." Id. at 633. Thus, the Court held "that a compulsory production of the private books and papers of the accused . . . is compelling him to be a witness against himself, within the meaning of the Fifth Amendment to the Constitution, and is the equivalent of a search and seizure -- and an unreasonable search and seizure -- within the meaning of the Fourth Amendment." 116 U.S. at 634-35. Not even a warrant supported by probable cause could mask the "'unreasonable' character of such seizures" and legitimize the use of those seized documents at trial. 116 U.S. at 633.