Article I, Section 3, Clause 6:
The Senate shall have the sole Power to try all Impeachments. When sitting for that Purpose, they shall be on Oath or Affirmation. When the President of the United States is tried, the Chief Justice shall preside: And no Person shall be convicted without the Concurrence of two thirds of the Members present.
The Senate enjoys broad discretion in establishing procedures to be undertaken in an impeachment trial. For instance, in a lawsuit challenging the Senate's use of a trial committee to take and report evidence, the Supreme Court in Nixon v. United States unanimously ruled that the suit posed a nonjusticiable political question and was not subject to judicial resolution.1 The Court explained that the term
try in the Constitution's provisions regarding impeachment was textually committed to the Senate for interpretation and lacked sufficient precision to enable a judicially manageable standard of review.2 In reaching this conclusion, the Court noted that the Constitution imposes three precise requirements for impeachment trials in the Senate: (1) Members must be under oath during the proceedings; (2) conviction requires a two-thirds vote; and (3) the Chief Justice must preside if the President is tried.3 Given these three clear requirements, the Court reasoned that the Framers
did not intend to impose additional limitations on the form of the Senate proceedings by the use of the word 'try.'4 Accordingly, subject to these three clear requirements of the Constitution, the Senate enjoys substantial discretion in establishing its own procedures during impeachment trials.
While the Senate determines for itself how to conduct impeachment proceedings, the nature and frequency of Senate impeachments trial are largely dependent on the impeachment charges brought by the House. The House has impeached 13 federal district judges, a judge on the Commerce Court, a Senator, a Supreme Court Justice, the secretary of an executive department, and two Presidents.5 But the Senate ultimately has only convicted and removed from office seven federal district judges and a Commerce Court judge.6 While this pattern obviously does not mean that Presidents or other civil officers are immune from removal based on impeachment,7 the Senate's acquittals may be deemed to have precedential value when assessing whether particular conduct constitutes a removable offense. For instance, the first subject of an impeachment by the House involved a sitting U.S. Senator for allegedly conspiring to aid Great Britain's attempt to seize Spanish-controlled territory.8 The Senate voted to dismiss the charges,9 and no Member of Congress has been impeached since. The House also impeached Supreme Court Justice Samuel Chase, who was widely viewed by Jeffersonian Republicans as openly partisan for, among other things, misapplying the law.10 The Senate acquitted Justice Chase, establishing a general principle that impeachment is not an appropriate remedy for disagreement with a judge's judicial philosophy or decisions.11