Definition
Impeachment has two distinct legal meanings that share a common core — calling something into question — but operate in entirely separate procedural contexts.
1. Constitutional Impeachment. The formal legislative process by which a deliberative body charges a public officer with misconduct in office. In the United States federal system, the House of Representatives holds the sole power to bring articles of impeachment; the Senate holds the sole power to try them. Conviction requires a two-thirds vote of the Senate and results in removal from office, with the possibility of disqualification from holding future office. Impeachment is not a criminal proceeding — it is a quasi-political process, and acquittal by the Senate does not bar subsequent criminal prosecution for the same conduct.
2. Evidentiary Impeachment. The process by which a party attacks the credibility of a witness during litigation. Impeachment of a witness does not mean accusing the witness of a crime; it means introducing evidence or eliciting testimony that gives the factfinder reason to doubt the witness's accuracy, truthfulness, or reliability. Common methods include confronting a witness with prior inconsistent statements, introducing evidence of prior convictions or character for untruthfulness, and demonstrating bias or motive to lie.
Common Language
Modern common usage (Wiktionary): The act of calling into question or challenging the accuracy or propriety of something; also, in law, a demonstration that a witness was less than truthful and is therefore less credible.
Historical common usage (Webster's 1913): A calling to account; arraignment, especially of a public officer for maladministration. Webster's also preserves an obsolete sense — hindrance or obstruction — now entirely gone from legal use.
The gap matters in two directions. In ordinary conversation, "impeachment" almost always refers to the constitutional removal process — most speakers are unaware that the term has a second, equally important legal meaning. Conversely, legal researchers focused on evidence and trial practice must not import constitutional associations into evidentiary impeachment, which has nothing to do with removal from office and everything to do with witness credibility mechanics.
Common Confusion
Constitutional impeachment is frequently misunderstood as equivalent to removal. It is not. Impeachment is the charge; removal is the outcome of conviction after trial. A public officer who has been impeached by the House has been accused, not removed. The distinction is constitutionally and historically critical — President Andrew Johnson and President Bill Clinton were both impeached and neither was removed.
Evidentiary impeachment is sometimes confused with rehabilitation or with introducing substantive evidence. Impeachment goes to credibility only; the fact that a prior inconsistent statement was made does not, without more, establish the truth of either statement.
Recognized Forms
/SUBTYPES
Evidentiary impeachment is recognized in several distinct forms under modern evidence rules:
- Impeachment by prior inconsistent statement: Confronting a witness with a prior statement that contradicts current testimony. Governed by FRE 613 in federal courts.
- Impeachment by character for untruthfulness: Introducing opinion or reputation evidence that a witness has a character for dishonesty, or evidence of prior convictions. Governed by FRE 608 and 609.
- Impeachment by bias or motive: Showing that a witness has a relationship, interest, or motive that may color the testimony. Not explicitly codified in the Federal Rules but universally recognized.
- Impeachment by contradiction: Introducing extrinsic evidence showing that something the witness said is factually wrong. Subject to the collateral matters doctrine, which limits when extrinsic contradiction evidence is permitted.
Why It Matters in Research
The double meaning is the primary trap. Historical sources — including all four source dictionaries here — treat constitutional impeachment as the primary or sole definition and give evidentiary impeachment little or no separate treatment. A researcher searching corpus sources for "impeachment" in an evidentiary context will surface constitutional material and vice versa. Filtering by surrounding context terms (witness, credibility, prior statement versus officer, articles, Senate) is essential.
Constitutional impeachment research must account for the federal/state split. State constitutions establish their own impeachment mechanisms, which often differ from the federal model in procedure, scope of covered officers, and standards of conduct. Corpus sources that describe "impeachment" in constitutional terms may be describing a state process that does not map directly onto the federal framework.
For evidentiary impeachment, the modern rules-based framework (Federal Rules of Evidence, adopted 1975) represents a significant restructuring of prior common law practice. Historical sources written before codification describe a more fragmented and jurisdiction-specific evidentiary landscape. The collateral matters doctrine, in particular, has been applied inconsistently across eras and jurisdictions, and historical dictionary definitions provide almost no guidance on how courts have drawn that line in practice. Researchers working in pre-FRE sources should expect significant variation and should not assume that historical impeachment rules track modern doctrine.
The obsolete sense flagged by Webster's 1913 — impeachment as obstruction or hindrance — appears in early English sources and in some colonial-era American legal documents. Researchers working in the earliest layers of the corpus should be alert to this usage, which has no modern counterpart in either the constitutional or evidentiary sense.
Historical Dictionary Support
All four source dictionaries lead with constitutional impeachment and treat it as the dominant or sole legal meaning. Bouvier offers the most constitutionally grounded treatment, quoting the relevant clauses of the U.S. Constitution directly and identifying the persons subject to impeachment. Rapalje & Lawrence most clearly articulates the bicameral structure — the lower house finds and prosecutes, the upper house tries — and correctly notes that the charges must involve great public offences, including treason, bribery, and high crimes and misdemeanors.
Black's (both editions) characterizes impeachment as a criminal proceeding before a quasi-political court, which requires some care. Federal impeachment is not a criminal proceeding in the technical sense; the quasi-political framing is closer to accurate and reflects the constitutional design. Using Black's language without that qualification could mislead researchers who then expect criminal procedure protections to apply.
None of the four source dictionaries gives substantive treatment to evidentiary impeachment as a distinct legal concept. This is a significant gap relative to modern legal practice, where evidentiary impeachment is encountered far more frequently than constitutional impeachment in day-to-day litigation. Researchers should not infer from the historical dictionaries' silence that evidentiary impeachment was unrecognized — it was well-established at common law — only that it was not considered a primary dictionary entry in that era.
Webster's 1913 preserves the obsolete hindrance sense and gives the removal/political sense as primary, which tracks the historical dictionaries. Wiktionary correctly identifies both the general credibility-challenge sense and the witness-specific evidentiary sense, making it the most useful common-language source for modern researchers navigating the term's full range.
Jurisdictional Note
Every U.S. state has its own impeachment mechanism established by its constitution, and the covered officers, procedural rules, and standards vary considerably. Some states permit impeachment of judges; others use separate removal mechanisms for judicial officers. Researchers should not assume that constitutional provisions or procedures from one jurisdiction describe another's impeachment process.
Encyclopedia Cross-Reference
civpro_176: Impeachment by Prior Inconsistent Statement — Rule 613 (The Law Mind Civil Procedure & Evidence Encyclopedia)
civpro_177: Impeachment by Contradiction and Collateral Matters Doctrine (The Law Mind Civil Procedure & Evidence Encyclopedia)
civpro_178: Impeachment by Character for Untruthfulness — Rules 608 and 609 (The Law Mind Civil Procedure & Evidence Encyclopedia)