CRS Report for Congress
Standard of Proof in Senate Impeachment
Thomas B. Ripy
Legislative Attorney
American Law Division
The Constitution gives the United States Senate the responsibility for trying
impeachments, but does not address the standard of proof that is to be used in such
trials. This report concludes that an examination of the constitutional language, history,
and the work of legal scholars provides no definitive answer to the question of what
standard is to be applied. In the final analysis the question is one which historically has
been answered by individual Senators guided by their own consciences.
At best, the constitutional provisions concerning the power of impeachment provide
only indirect guidance in analyzing the question of what standard of proof is, or should
be, applicable to Senate impeachment trials. Nevertheless, those words are the starting
point for discussions about the nature of impeachment proceedings and the standard of
proof that is or should be applicable to such proceedings. The role of each house of
Congress is outlined in Article I. Briefly, the Constitution confers on the House of
Representatives “the sole Power of Impeachment.” A bit more is said of the role of the1
The Senate shall have the 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.
Judgment in Cases of Impeachment shall not extend further than removal from
Office, and disqualification to hold and enjoy any Office of honor, Trust or Profit
under the United States: but the Party convicted shall nevertheless be liable and2

subject to Indictment, Trial, Judgment and Punishment, according to Law.
U.S. Const., Art. I, Sec. 2, clause 5.1
U.S. Const., Art I, Sec. 3, clauses 5 and 6.2
Congressional Research Service ˜ The Library of Congress

Impeachment is also addressed in the Executive Article of the Constitution wherein it is
said that: “The President, Vice President, and all Civil Officers of the United States, shall
be removed from Office on Impeachment for and Conviction of, Treason, Bribery, or
other high Crimes and Misdemeanors.” Finally, the Judicial Article provides that, “The34
trial of all Crimes except Impeachment, shall be by Jury; ....” These few words provide
the constitutional framework for a discussion of the standard of proof in impeachment
proceedings, but no definitive answer as to what standard is to or should be applied.
The use of certain words such as “try,” “convicted” and “conviction” suggests that
impeachment might be likened to a criminal proceeding, where the standard of proof is
beyond a reasonable doubt. This position was enunciated in the Minority Views
contained in the Report of the House Judiciary Committee on the impeachment5
proceedings against President Nixon. In their view the appropriate standard of proof for
the Senate was that applicable to criminal cases. For support they rely, in part, on the6
constitutional language cited above.
The position that proof beyond a reasonable doubt is required has been advanced, as
one might expect, by defendants in impeachment proceedings, while the House Managers
(who present the case for conviction) have urged a lower civil standard - preponderance
of the evidence. Thus, in the Senate trial of the impeachment of Judge Harry Claiborne
in 1986, his attorneys filed a motion to designate beyond a reasonable doubt as the
applicable standard for the Senate in reaching its determination. In the brief in support
of the motion they argued that the constitutional language made it clear that an
impeachment trial was in the nature of a criminal proceeding; the standard of proof in all
criminal trials is beyond a reasonable doubt; historically impeachments have been
conducted in the nature of a criminal proceeding; and the consequences for the defendant
were grave, requiring the prosecutors to be held to the highest standard of proof, beyond
a reasonable doubt.7
The response of the House Managers in opposition to the Claiborne motion noted
that the reasonable doubt standard was designed to protect criminal defendants who risked
“forfeitures of life, liberty and property.” (Quoting Brinegar v. United States, 338 U.S.

160, 174 (1949)) Such a standard was inappropriate, they maintained, because the

U.S. Const., Art. II, Sec. 6.3
U.S. Const., Art. III, Sec. 2, clause 3.4
H.Rept. 93-1305 at 377-381.5
Because of the nature of the impeachment and trial process and the different roles played6
by the Senate and House of Representatives, the minority felt it necessary to examine the
standard appropriate for the Senate as a predicate to any attempt to assess the appropriate
standard for a proceeding in the House. Their analysis led them to conclude that the appropriate
standard for the Senate was beyond a reasonable doubt (H.Rept. 93-1305 at 379-80) and for the
House, clear and convincing evidence (Id. at 381).
Gray & Reams, The Congressional Impeachment Process and the Judiciary: Documents7
and Materials on the Removal of Federal District Judge Harry E. Claiborne , Volume 5,
Document 41 (Motions Referred to the Senate by the Senate Impeachment Trial Committee), IX
(Judge Claiborne’s Motion to designate “Beyond a Reasonable Doubt” as the Standard of Proof
in the Impeachment Trial (and supporting memorandum)) (1987) (hereinafter GRAY & REAMS).

Constitution limits the consequences of a Senate impeachment trial to removal from
office and disqualification from holding office in the future, explicitly preserving the
option for a subsequent criminal trial in the courts. Added support for their position was
drawn from the fact that the framers, while borrowing some terms associated with
criminal law from the English impeachment model, expressly rejected the English
practice allowing the imposition of traditional criminal punishment, including forfeitures
of life, property and liberty. Contrary to the defendant, they found that historically, the
Senate had rejected the analogy to a criminal proceeding, citing the Ritter impeachment8
in 1936 as precedent.
During the course of the floor debate on these motions the attorney for Judge
Claiborne quoted statements by Senators Robert Taft, Jr., Sam Ervin, StromThurmond,
and John Stennis indicating that they would apply the beyond a reasonable doubt standard
if the case against President Nixon came before the Senate. Representative Kastenmeier
responded for the House repeating the arguments contained in the memorandum in
response summarized above and stressing 1) that the Senate had never adopted such a
standard of proof; 2) that the statements quoted were expressions of individual intent
only and not binding on the Senate as a body; 3) that the proceeding was not a criminal
trial and use of the criminal standard was inappropriate where the public interest in
removing corrupt officials was a significant factor; and 4) that historically, the Senate had9
allowed each member to exercise personal judgment in these cases.
During the consideration of the motion by Judge Claiborne to designate beyond a
reasonable doubt as the standard of proof, the question was posed as to the consequences
of voting the motion down. Senator Humphrey asked what the standard would be if the
motion was rejected, Senator Metzenbaum asked whether rejection left an inference that
the reasonable doubt standard was not applicable, and Senator Heflin questioned whether
rejection would prevent an individual Senator from applying the reasonable doubt
standard. The response of the Presiding Officer was that rejection of the motion left
individual members free to apply a standard of their choice, including, but not limited to
the reasonable doubt standard. Judge Claiborne’s motion was rejected by the Presiding
Officer, holding that the standard to apply was up to each Senator to decide individually.
Senator Hatch requested the yeas and nays and the motion was rejected by a vote of 17
yeas and 75 nays. 10

Gray & Reams, Volume 5, Document 41, X (House Manager’s opposition to Motion to8
Designate “Beyond a Reasonable Doubt” as the Standard of Proof). In essence, their argument
was that since criminal sanctions could not be imposed, a criminal standard of proof was not
required. Additionally, they contended that the criminal standard was inappropriate in an
impeachment because impeachment was by its nature a proceeding where the public interest (the
interests of society) weighed more heavily than the interests of the individual defendant, which
were adequately protected by the constitutional requirements of separate action by both Houses
of Congress and a two-thirds vote of those present for conviction in the Senate. They urged a
preponderance standard. This contrasts with the view of the House Judiciary Committee minority
in the case of President Nixon, where the beyond a reasonable doubt standard was urged. See,
fn.6 and accompanying text.

132 Cong. Rec. S15489 - S15490 (daily ed. October 7, 1986).9

132 Cong. Rec. S15506 - S15507 (daily ed. October 7, 1986).10

While the Senate refused to impose the reasonable doubt rule as the Senate standard,
individual members undoubtedly applied that standard in their own minds when weighing
the sufficiency of the evidence in the Claiborne case. Presumably, at least the seventeen
who voted in favor of the motion to adopt the standard, followed it in their deliberations.
In explaining his vote on the articles of impeachment in the Claiborne case, Senator Hatch
makes it clear that he followed that standard: “Relying as they did on the criminal
conviction, the House Articles of Impeachment required the Senate to ascertain whether,
beyond a reasonable doubt, Judge Claiborne intentionally filed a false return.”11
The issue was revisited during discussions at the organizational meeting of the
Senate Impeachment Trial Committee for consideration of the articles of impeachment
against Judge Alcee Hastings. Senator Lieberman asked help in understanding what12
guidance the common law of American impeachment provided as to the “threshold the
evidence has to cross for us to make a judgment of guilt or innocence against this
judge.” In response, Senator Rudman said: 13
I don’t think you are going to find one, Joe. I think it is going to be whatever
you apply to it. We looked through that last time, and you are not going to find it. It
is what is in the mind of every Senator. If you want to use clear and convincing,
preponderance, if you want to use beyond a reasonable doubt—I think it is what14
everybody decides for themselves.
Asked for his comments, Michael Davidson (Senate Legal Counsel) reviewed the history
of the Claiborne impeachment and the debate and vote on the standard of evidence in that
case. Noting that the Senate had overwhelmingly rejected the motion to establish beyond
a reasonable doubt as the Senate standard, leaving that determination to each individual
member, he suggested that historical records and commentary might provide insight for15
an individual making these judgments, but do not provide any single definitive answer.
Some commentators have urged a middle ground between the usual civil standard
and the criminal standard of proof. Noting that impeachment is serious business but that
the usual criminal sanctions of fines and imprisonment are denied the Senate, Professor
Rotunda suggests that the appropriate standard of proof should be “clear and convincing
evidence.” This is an intermediate standard used in some important civil cases, more than
a preponderance and less than a reasonable doubt. “Clear and convincing evidence is

132 Cong. Rec. S15763 (daily ed. October 9, 1986); Senator Bingaman also applied the11

criminal standard, id.
Report of the Senate Impeachment Trial Committee on the Articles Against Judge Alcee12
Hastings: Hearings before the Senate Impeachment Trial Committee (hereinafter Hastingsstst
Report) (Part 1 of 3) 101 Cong., 1 Sess. 73-75, discussion involving Senator Lieberman,
Senator Rudman, and Mr. Davidson.
Id. at 74.13
Id. 14
indicated a preference for a middle level of proof. (135 Cong. Rec. 25337) Senator Specter
indicated that in this case, where the Judge had been acquitted in a criminal trial, he would apply
the reasonable doubt standard of criminal law. (135 Cong. Rec. 25347)

typically defined as that measure or degree of proof which will produce in the mind of the
trier of facts a firm belief or conviction as to the allegation sought to be established.” 16
The National Commission on Judicial Discipline and Removal decided not to
recommend the adoption of a standard of proof. Nevertheless, its report provides an
illuminating discussion of the issue.
Standards of Proof. The Question remains: what is the appropriate standard
of proof for Senate impeachment proceedings? The Senate has declined to establish
a standard, leaving it a matter for the conscience of each Senator. The disadvantage
of this practice is that the respondent judge, the House Managers, and, indeed the
Senators themselves cannot know in advance what standard the Senate will apply.
The Commission considered whether it would be desirable, as a matter of policy,
for the Senate to prescribe a standard to guide participants in their preparation for
impeachment trials. The Senate could choose from among three established
standards: beyond a reasonable doubt, clear and convincing, and preponderance of
Some Senators favor the beyond a reasonable doubt standard because of their
concerns about the separation of powers and because impeachment proceedings
parallel criminal trials. If the Senate is impeaching based on a prior felony conviction
(which requires the jury to find commission of an offense beyond a reasonable doubt)
then the Senate should use the same standard, some argue.
Others claim that the beyond a reasonable doubt standard is too deferential to the
convicted judge and fails sufficiently to recognize the purpose of impeachment —
namely, to defend the community against abuse of power by judges. The purpose of
an impeachment proceeding is different from the purpose of a criminal trial, they
argue. In a criminal proceeding, a court may take a defendant’s life, liberty, or
property, whereas an impeachment proceeding involves a respondent’s office.
Impeachment is a political proceeding, and in their view the lower standard of
“preponderance of the evidence” is therefore the appropriate one.
Still others have argued that the appropriate standard of proof is clear and
convincing evidence that the respondent has committed an impeachable offense. It
gives force to the purpose of remedying judicial abuse of power, while recognizing
the competing interests of avoiding unjustified removals and protecting judicial
In the final analysis, the Commission recognizes that each Senator is both judge
and juror. As observed by Senate Legal Counsel Michael Davidson, it is the sum of
Senators’ separate judgments that amounts to either conviction or acquittal: “any
member is entitled to establish the highest, the medium, [or] a lower standard to17

govern his or her analysis of the evidence.”
Rotunda, An Essay on the Constitutional Parameters of Federal Impeachment, 76 Ky.16
L.J. 707, 719-20 (1988).
Report of the National Commission on Judicial Discipline & Removal at 59-60 (August17


While the report focuses on the impeachment of judges, similar competing
considerations may come into play when executive branch officials are the subjects of an
impeachment proceeding. In 1974, with a possible presidential impeachment as an
impetus, Professor Charles L. Black, Jr. published his IMPEACHMENT: A HANDBOOK. In
it he discusses the conflicting policy considerations of an impeachment in the context of
the trial of a President. In response to a rhetorical question as to the “right standard for
judging guilt in an impeachment proceeding,” he replies:
Of course we don’t know the answer with any sureness; we have to work it out
for ourselves. As with so many constitutional questions, we have to ask what is
reasonable, and the reply here is far from obvious. Removal by conviction on
impeachment is a stunning penalty, the ruin of a life. Even more important, it unseats
the person the people have deliberately chosen for the office. The adoption of a
lenient standard of proof could mean that this punishment and this frustration of
popular will, could occur even though substantial doubt of guilt remained. On the
other hand, the high “criminal” standard of proof could mean, in practice, that a man
could remain president whom every member of the Senate believed guilty of
corruption, just because guilt was not shown “beyond a reasonable doubt.” Neither
result is good; law is often like that.
Of course each Senator must find his own standard in his own conscience, as
advised by reflection. The essential thing is that no part whatever be played by the
natural human tendency to think the worst of a person of whom one generally
disapproves, and the verbalization of a high standard may serve as a constant reminder
of this. Weighing the factors, I would be sure that one ought not to be satisfied, or
anything near satisfied, with the mere “preponderance” of an ordinary civil trial, but
perhaps must be satisfied with something less than the “beyond a reasonable doubt”
standard of the ordinary criminal trial, in the full literal meaning of that standard.
“Overwhelming preponderance of the evidence” comes perhaps as close as can to
denoting the desired standard. A unique rule, not yet named by law, may find itself,
in the terrible seriousness of a great case. Senators have no plainly authoritative guide
in this matter, and ought not be censured for the rule they conscientiously choose to
act upon, after thought and counsel, and above all in total awareness of the dangers18
of partisanship or feelings of distaste.
In sum, the Senate has traditionally left the choice of the applicable standard of proof
to each individual Senator. While rejecting a motion to make the criminal standard the
standard in the Claiborne impeachment, the discussion made clear that it was simply a
decision to allow each member to make that choice and not a repudiation of the standard
itself. Individuals might apply that or any other standard of their choice. A walk through
history and an examination of the discussions of legal commentators may aid individuals
in weighing their choices, but provides no definitive answers. Indeed, such an exercise
is perhaps most useful in highlighting basic questions that members will want to ask
themselves when searching for the appropriate standard.

C. Black, Impeachment: A Handbook, at 17-18 (1974). 18