354 U.S. 449 (1957), argued 1 Apr. 1957, decided 24 June 1957 by vote of 9 to 0; Frankfurter for the Court. Although the power of the Supreme Court to overturn state convictions is limited to the enforcement of Fourteenth Amendment due process rights, the Court may formulate rules of evidence in the exercise of its “supervisory power” over the administration of federal criminal justice that go well beyond due process requirements. The best-known example is the McNabb-Mallory rule.
Kamisar, Yale. "Mallory v. United States." In The Oxford Guide to United States Supreme Court Decisions. 2d ed., edited by K. L. Hall and J.W.Ely Jr., 200-1. Oxford: Oxford Univ. Press, 2009.