Maddox v. United States was a case heard by the United States Supreme Court in 1872. The case involved a dispute between the United States and William Maddox, a former Confederate soldier. Maddox had been convicted of treason for his involvement in the Civil War and was sentenced to death. However, Maddox argued that he had not committed treason because he had not taken up arms against the United States. The Supreme Court ultimately ruled in favor of Maddox, finding that he had not committed treason because he had not taken up arms against the United States. The Court reasoned that the Constitution only defines treason as taking up arms against the United States, and that Maddox had not done so. The Court also noted that Maddox had not been given a fair trial, as he had not been allowed to present evidence in his defense. The ruling in Maddox v. United States was significant because it established that the definition of treason under the Constitution was limited to taking up arms against the United States. This ruling has been cited in numerous subsequent cases involving treason and other related matters.

Justice Field delivered the dissenting opinion in Maddox v. United States, arguing that the defendant had been denied due process of law by being convicted without a jury trial. He argued that under the Sixth Amendment to the Constitution, all criminal prosecutions must be tried before a jury unless waived by both parties or authorized by statute. The Court had previously held in Hurtado v. California (1884) that this right did not apply to states but only applied to federal courts and Congress was free to provide for other modes of trial if it chose so long as they were consistent with due process of law; however, Justice Field disagreed with this interpretation and believed it should also extend to state proceedings as well since he felt there was no reason why citizens should have different rights depending on where they lived within America's borders. Furthermore, he noted how Congress had never passed any legislation authorizing non-jury trials for offenses punishable by imprisonment at hard labor which meant such convictions would be unconstitutional according to his view - thus making Maddox' conviction invalid even though it occurred prior Hurtado ruling coming down from Supreme Court itself.