In the United States, a federal impeachment trial is held as the second stage of the U.S. federal government's two-stage impeachment process. The preceding stage is the "impeachment" itself, held by a vote in the United States House of Representatives. Federal impeachment trials are held in the U.S. Senate, with the senators acting as the jurors. At the end of a completed impeachment trial, the U.S. Senate delivers a verdict. A "guilty" verdict (requiring a two-thirds majority) has the effect of immediately removing an officeholder from office. After, and only after, a "guilty" verdict, the Senate has the option of additionally barring the official from ever holding federal office again, which can be done by a simple-majority vote.

Officers and other key figures in an impeachment trial Presiding officer

Per Article I, Section 3, Clause 6 of the US Constitution, the chief justice serves as the presiding officer in a trial of an incumbent president. This provision prevents the vice president, who is the president of the Senate and generally holds the authority to preside over Senate business, from overseeing an impeachment trial that would elevate him or her to the presidency if the president were removed. This was particularly important at the time of the Constitution's writing, as, before the reforms of the Twelfth Amendment to the Constitution, presidents and vice presidents were not elected together on tickets and could potentially be of rival political factions. The Constitution does not specify who should serve as the presiding officer of impeachment trials of persons other than incumbent presidents. In such impeachments, the presiding officer has most often been the president of the Senate, meaning either the vice president of the United States or (in the vice president's absence) the president pro tempore of the Senate. Other trials have had a senator other than the president pro tempore serve as presiding officer, with such a senator having been chosen to preside by a vote of the Senate.

The presiding officer can rule on questions, such as those related to the admission of evidence. Their rulings stand as the Senate's judgment on those particular questions unless the Senate votes to overrule them. Alternatively, the presiding officer can forgo ruling on a question and directly submit it to a Senate vote. Senators who act as the presiding officer of an impeachment hearing are still permitted to vote in the trial.

In the 1999 impeachment trial of President Bill Clinton, the second instance of a presidential impeachment, Chief Justice William Rehnquist was an intentionally passive presiding officer, once commenting on his stint as presiding officer, "I did nothing in particular, and I did it very well."

In a 2011 journal article, Roy E. Brownell II posited the view that when a chief justice presides over a presidential impeachment trial, they are temporarily acting as an officer of the legislative branch rather than as a member of the judiciary. Brownell pointed to the fact that senate impeachment trials and the chief justice are not included within Article III of the Constitution (which establishes the judiciary), but are instead solely contained within Article I (establishing the legislature) to argue that in the context of their performance at presiding over presidential impeachment trials, the chief justice is acting as an effective member of legislative branch. Additionally, Brownell pointed to the practice of senators being able to overrule a chief justice's rulings as presiding officer as tacit affirmation that such rulings are made as a legislative officer rather than a judge. Brownell argued that the practice of permitting the Senate to override the chief justice during the trials affirms this due to the fact that the Supreme Court had ruled that congress lacks power to invalidate final judicial rulings (Plaut v. Spendthrift Farm, Inc., 514 U. S. 211 (1995)). He also noted to the fact that chief justices having at times been addressed as "Mr. President" rather than "your honor" during impeachment trials as being a tacit acknowledgement of this.

The second impeachment trial of Donald Trump (the only impeachment trial of a former president) was presided over by then-Senate President Pro Tempore Patrick Leahy due to Trump no longer being president when the trial began.

Role of senators

In impeachment trials, the senators are generally referred to as acting as jurors. However, the 1999 impeachment trial of President Bill Clinton, Senator Tom Harkin objected to the use of the term "jurors", and Chief Justice William Rehnquist agreed with Harkin's position over that of the House impeachment managers (prosecutors), declaring, "The chair is of the view that the senator from Iowa's objection is well taken, that the core - the Senate is not simply a jury. It is a court in this case. And therefore, counsel should refrain from referring to the senators as jurors." This indicated a belief that the senators collectively take on a role that is perhaps more akin to a judge than to a jury.

Under Senate rules for impeachment trials, senators are able to call and subpoena witnesses for a trial. Senators are also able to submit written questions to witnesses as well as the prosecution and the defense.

If they desire, any senator may be excused from serving their role in an impeachment trial.

Rule XI trial committees A Rule XI trial committee is a committee of senators that the Senate may appoint to receive evidence and hear testimony by witnesses on behalf of the Senate, reporting back to the full Senate and providing the full senate with a certified transcript of the proceedings that they witnessed. The use of such a committee allows for the majority of Senators to be absent during the presentation of evidence and witness testimony heard by the committee. Without use of such a committee, all senators would have to be present at the presentation of all evidence and witness testimony. Rule XI committees have been utilized in for four impeachment trials: the 1986 impeachment trial of Judge Harry E. Claiborne, the 1989 impeachment trials of Judges Walter Nixon and Alcee Hastings, and the 2010 trial of Judge Thomas Porteous.

Prosecution House impeachment managers

The U.S. House of Representatives appoints impeachment managers, a committee of members of the House who, together, act as the prosecutors in the impeachment trial.

While they are always approved by House vote, how the initial decision of who serves as a manager is arrived at has differed between impeachments. In some impeachments, the House managers have been chosen upon the recommendation of the Chairman of the House Committee on the Judiciary. Another way that has been used is by having the whole house decide by balloting who should serve. In some other impeachments, the speaker of the House has chosen the slate of impeachment managers and the House cast a vote approving the speakers' selections.Multiple sources:

Legal counsel Outside legal counsel can also be hired to provide advice to the impeachment managers. This was the case, for instance, in both the first and second impeachment trials of Donald Trump.

Defense

Impeached officeholder An impeached officeholder may appear at their impeachment trial. They may also opt not to appear in-person and instead be represented entirely through counsel.

Private counsel In impeachment trials, an impeached officeholder can be represented by private counsel.

House defense team In Donald Trump's first impeachment trial, in addition to private counsel, he had several House members (all belonging to his political party) serve on his defense.

Rules

Constitutional The Senate is granted the sole authority to try impeached individuals. Impeachment and impeachment trials are provided for by section four of Article Two of the Constitution. Impeachment trials are further outlined in section three, clause six of Article One of the Constitution.

The Constitution requires that a two-thirds majority vote "guilty" in order for an individual to be convicted and removed from office. There is no process provided to appeal an impeachment verdict. The Constitution also specifies that, after a conviction, the Senate may vote to additionally bar an individual from again holding federal office. The majority needed for this second matter is not specified by the Constitution, and the Senate has, in practice, used a simple majority vote for this.

The Constitution does not elaborate on specifications on the workings of an impeachment trial. Its only further specifications are that the chief justice of the United States presides over presidential impeachment trials, and that each senator must swear an oath. Therefore, the remainder of the mechanics of impeachment trials are left to the determination of the Senate itself.

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.

Rules in use since 1868 The exact language of the rules used for previous trials could not be utilized for 1868 impeachment trial of President Andrew Johnson because those rules used wording specific to a trial being presided over by an officer of the Senate (as had been the case for all previous impeachment trials), while the Constitution stipulated that impeachments trials for incumbent presidents are to be presided over by the chief justice of the United States. 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". Very few changes have been made to these rules since 1868. 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.

Among other things, the rules specify what oaths must be said and the order certain events are to occur in. However, many important matters are left unspecified by these rules.

The Senate rules states that, as soon as impeachment managers are appointed, the Senate must "immediately" receive them.

The impeached official may appear in person at their trial. They may, alternatively, opt not to appear in person at their trial, instead being represented solely through counsel.

Rule XI

Rule XI, allowing for the appointment of "Rule XI committees" was adopted by the Senate in 1934 as a simple resolution offered by Senator Henry F. Ashurst. Rule XI states,

This rule change was motivated by the 1933 impeachment trial of Judge Harold Louderback, which highlighted the difficulties that could be brought by requiring a plenary session of the senate for all aspects of a lengthy impeachment trial during a busy legislative period.