Constitutional The Senate is granted the sole authority to try impeached individuals. The Constitution does not elaborate on specifications on the workings of an impeachment trial.
Senate-adopted rules Early Senate trials The first two impeachment trials in United States history (those of
William Blount and
John Pickering) had each had their own individual set of rules. The nineteen rules established for
the trial of
Samuel Chase appear also to have been used for the later trials of
James H. Peck and
West Hughes Humphreys. Because of this, a
select committee of senators was tasked with developing rules to be used in the impeachment trial of Johnson. The select committee decided that they would create permanent rules that would be used for any future impeachments, declaring it to be, "proper to report general rules for the trial of all impeachments". Indeed, since 1868, impeachment trials in the U.S. Senate have been governed by the rules created for the impeachment trial of Andrew Johnson, known as the "Rules of Procedure and Practice in the Senate when Sitting on Impeachment Trials". The rules were not altered until after the 1933 impeachment trial of
Harold Louderback, when a single rule change was made. In the 1970s, the
Senate Committee on Rules and Administration explored the possibly of altering the rules in advance of an anticipated impeachment trial that might have resulted from the
impeachment process against Richard Nixon, but after to
Nixon resigned without being impeached and convicted, this was momentarily abandoned. The rule changes explored in the 1970s were not adopted until the Senate acted upon a further recommendation to adopt them in 1986. No further changes have been made since to the rules outlined for the Johnson trial. The Senate rules states that, as soon as impeachment managers are appointed, the Senate must "immediately" receive them. The constitutionality of this rule change was called into question by some senators soon after its passage, motivating the Senate to opt against using a rule committee for the 1936 impeachment trial of Judge
Halsted L. Ritter. Its constitutionality was tested by the
Supreme Court of the United States in the 1993
Nixon v. United States case, arising from the 1989 impeachment trial of Walter Nixon, in which the Supreme Court upheld the United States Senate's authority to determine its own procedures, which includes its decision to opt for use of Rule XI trial committees. Since the impeachment trials are not legally bound to any statutory evidentiary rules, arguments about the admissibility of evidence during the trials are often argued on the basis of Senate precedent. Such precedent, however, is merely persuasive and not binding. Under the procedures that current Senate rules for impeachment trials create, objections on the admissibility of evidence are first ruled upon by the presiding officer, with a majority vote of the Senate being capable overruling a decision by the presiding officer. The rules state that while the presiding officer has the authority to rule on "questions of relevancy, materiality, and redundancy of evidence and incidental questions", the Senate reserve the right to "questions of relevancy, materiality, and redundancy of evidence and incidental questions". Implicit in these rules is that some basic standard of relevancy is expected for evidence to be admissible. In more recent impeachment trials, parties have often cited the
Federal Rules of Evidence as persuasive authority in motions to either include or exclude evidence from an impeachment trial. A 2023
Congressional Research Service report observed that the Senate has acted receptively of these rules being cited as persuasive authority.
Other matters An impeachment trial can be
adjourned sine die at any time by a simple majority vote, effectively ending a trial without completion. This precedent was cited in the Senate's decision to commence with the second impeachment trial of Donald Trump after he had already left office. In 2021,
University of Alabama School of Law professor Ronald Krotoszynski wrote an article in
Politico opining that it is possible for the Senate to end the argument phase of an impeachment trial early and move instead to closing arguments if it took a majority vote in favor of a motion to do so. He likened it to a motion for
summary judgement in a civil court. The Senate has, by majority votes, multiple times judged that an individual impeached while in office can still be subjected to a trial, conviction, and the penalty of disqualification even after they leave office. Both the Senate and the House have, in the past, judged themselves to be able to utilize their impeachment authorities on former officeholders. The principal precedent for both impeaching a former officeholder and for holding an impeachment trial of a former officeholder is the impeachment and impeachment trial of
William W. Belknap, who had resigned as Secretary of War hours before he was impeached in 1876. Many scholars have argued that if impeachment could not apply to former officeholders, then the Senate's power to disqualify individuals from holding future federal office through an impeachment process would be greatly weakened, as there would be a loophole of resigning before this sentence is imposed by the Senate. Since the Senate does not need to hold an impeachment trial after a House impeachment, it can also choose not to hold trials in instances where individuals resigned following impeachment. Of the twenty-one individuals to be impeached by the United States House of Representatives, only
Mark W. Delahay did not face a trial, as the Senate decided not to hold a trial into him after he resigned his office following his impeachment by the House. A trial can also be dismissed without completion. This has been done before in instances when officeholders resigned partway into an impeachment trial against them. The House and the Senate have both each once moved to dismiss impeachment proceedings against officials that resigned partway in to impeachment trials. The Senate did this in 1926 by dismissing the proceedings against Judge
George W. English. The House did this by passing a
simple resolution in 2009 to end the proceedings against Judge
Samuel B. Kent. This also includes guidelines governing the presence of news media within the Senate Chamber. The rules adopted regarding press coverage within the Senate chamber have differed between impeachment trials. ==Proceedings of an impeachment trial under current conventions==