Watkins v. United States was a Supreme Court case that addressed the scope of the Fifth Amendment's protection against self-incrimination. The case involved John Watkins, a former Confederate soldier who was called to testify before a congressional committee investigating the Ku Klux Klan. Watkins refused to answer questions about his involvement in the Klan, citing his Fifth Amendment right against self-incrimination. The committee held Watkins in contempt and he was convicted in a criminal trial. The Supreme Court heard the case and ruled in favor of Watkins. The Court held that the Fifth Amendment's protection against self-incrimination applied to congressional investigations, and that Watkins could not be compelled to answer questions that might incriminate him. The Court also held that the Fifth Amendment's protection applied to all branches of the federal government, not just the judicial branch. The ruling in Watkins v. United States established an important precedent for the protection of individuals' rights against self-incrimination. The decision has been cited in numerous subsequent cases, and it remains an important part of the legal landscape today.

In Watkins v. United States, the Supreme Court was asked to decide whether a witness could be compelled to answer questions posed by Congress in an investigation into alleged fraud and corruption within the government. The majority opinion held that Congress had the power to compel witnesses to testify before it, even if their testimony might incriminate them or lead to criminal prosecution. Justice Field dissented from this ruling, arguing that such a broad interpretation of congressional authority violated both the Fifth Amendment's protection against self-incrimination and Article I of the Constitution which grants only limited powers over individuals for legislative purposes. He argued that while Congress has some investigative powers with respect to its own members' conduct, it does not have unlimited authority over citizens who are not part of its proceedings. Furthermore, he argued that forcing someone under threat of punishment or imprisonment is unconstitutional as it violates due process rights guaranteed by both federal law and state constitutions alike.