Definition
Perjury is the criminal offense of knowingly making a false statement of fact under oath or affirmation in a judicial or official proceeding, where the statement is material to the proceeding. It is an offense against the administration of justice: the harm is not merely that the speaker lied, but that a false statement was injected under oath into a proceeding in which truth is legally required and relied upon.
The offense has several components that must all be present. The speaker must have been lawfully sworn or affirmed. The statement must have been false. The speaker must have known it was false at the time — honest mistake, faulty memory, or good-faith belief in a wrong answer does not constitute perjury. And the false statement must have been material — that is, capable of influencing the tribunal or outcome, even if it did not actually do so.
At common law, perjury was limited to false testimony in judicial proceedings. Modern statutes in virtually every American jurisdiction and at the federal level extend the offense to sworn statements in a broader range of official contexts: grand jury proceedings, depositions, sworn affidavits, administrative hearings, and legislative proceedings.
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Common Language
Modern common usage (Wiktionary): "The deliberate giving of false or misleading testimony under oath."
Historical common usage (Webster's 1913): "The act or crime of willfully making a false oath or affirmation, or of testifying falsely in a judicial proceeding, touching a matter material to the issue or point in question."
The common and legal definitions are close, but the gap lies in the materiality requirement and the mental state element. Ordinary usage treats any deliberate lie under oath as perjury. Legal doctrine does not: a knowingly false statement about an immaterial matter does not satisfy the offense, and courts have occasionally dismissed perjury charges on precisely this ground. The "willfully" language in Webster's maps roughly to the legal knowledge requirement, but legal analysis is more exacting — good-faith belief in a false statement, however unreasonable, is a defense.
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Common Confusion
Perjury is frequently confused with two related but distinct offenses.
False statements (at the federal level, 18 USC 1001) do not require the speaker to be under oath — they reach any knowingly false material statement made to a federal agency or in a federal matter. Perjury requires the oath; false statements statutes do not. Federal prosecutors often have tactical reasons to charge one rather than the other.
Subornation of perjury is a separate offense: procuring or inducing another person to commit perjury. The suborner need not personally testify falsely; liability arises from causing the perjured testimony of another.
Obstruction of justice can overlap with perjury in fact patterns but is a broader category addressing interference with proceedings through any corrupt means, not limited to sworn false statements.
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Core Elements
The standard common law and modern statutory formulation requires:
1. A lawful oath or affirmation — administered by a person authorized to administer it, in a proceeding where an oath is legally required or permitted.
2. A false statement of fact — opinion or legal conclusion, as distinct from fact, has sometimes been held outside the scope of perjury, though modern courts vary.
3. Knowledge of falsity — the speaker must know the statement is false at the time it is made. Willful blindness may satisfy this element under some statutes.
4. Materiality — the false statement must be capable of affecting the proceeding, outcome, or inquiry. Falsity about a peripheral or irrelevant matter will not suffice.
Some modern statutes add an inconsistent-statements theory: a witness may be convicted of perjury by proof that they made two irreconcilable sworn statements, without the prosecution having to prove which one was false.
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Why It Matters in Research
The materiality element is the central doctrinal trap in perjury research. Historical sources treat it as settled that materiality is required, but they diverge on who decides materiality (judge or jury) and how broadly it is measured. Researchers working in federal materials should note that the Supreme Court addressed the judge/jury question directly, establishing that materiality is an element for the jury under due process principles — a development post-dating all historical dictionary sources.
The two-witness rule is another historical trap. At common law, perjury could not be proved by the uncorroborated testimony of a single witness — the theory being that a conviction could not rest on one oath against another. Many historical sources treat this rule as foundational. Its status in modern American law is substantially eroded: federal courts and most state courts have relaxed or abolished it, allowing conviction on a single witness's testimony corroborated by other evidence. Researchers relying on Rapalje & Lawrence or similar nineteenth-century sources for perjury procedure should verify whether the jurisdiction at issue still follows the rule.
The scope of covered proceedings expanded significantly in the twentieth century. Historical dictionary definitions reflect the common law's judicial-proceeding limitation. Modern statutes — federal and state — reach depositions, administrative hearings, grand jury testimony, and sworn statements to agencies. This means a case that would not have been cognizable as perjury at common law may be squarely within a modern statute.
Researchers in the Law Mind corpus should follow the connection to 18 USC 1001 false statements carefully. The corpus encyclopedia entry covers both offenses together because federal practitioners regularly face the choice between them, and the doctrinal overlap (particularly on the materiality element) generates substantial case law applicable to both.
Recantation is a limited but genuine defense in some jurisdictions — a witness who corrects false testimony before it substantially affects the proceeding may avoid liability under certain statutes. Historical sources generally do not address recantation as a defense.
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Historical Dictionary Support
Rapalje & Lawrence define perjury as "the willful assertion, as to a matter of fact, opinion, belief, or knowledge, made by a witness in a judicial proceeding as part of his evidence, either upon oath or in any form allowed by law to be substituted for an oath, whether such evidence is given in open court, on a trial or otherwise, or in an affidavit." The definition is notably comprehensive for its era in extending beyond open-court testimony to affidavits, though it retains the judicial-proceeding frame.
Rapalje & Lawrence are useful in flagging the opinion/belief problem: their definition includes assertions "as to opinion or belief," whereas strict common law authorities sometimes held that a false statement of opinion could not be perjury because the speaker's private mental state was not provably false in the same sense as an objective fact. Modern statutes largely cut through this debate by focusing on the speaker's knowledge at the time of the statement rather than the nature of the assertion.
The historical sources share a common silence on inconsistent-statements perjury, which is a product of twentieth-century legislative development. They also do not address federal-agency false statement liability, which postdates the corpus by decades. On the core elements — oath, falsity, knowledge, materiality — there is broad agreement across historical dictionaries, with variation mainly in how they articulate the two-witness rule.
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Jurisdictional Note
State perjury statutes vary on whether materiality must be proved as an element or is treated as a jurisdictional prerequisite, on the survival of the two-witness rule, and on whether recantation constitutes a defense. Federal perjury under 18 USC 1621 and the separate false declarations statute 18 USC 1623 (covering false declarations before courts and grand juries) operate in parallel with distinct procedural rules, and the inconsistent-statements theory is expressly available under 18 USC 1623 but not under 1621.
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Encyclopedia Cross-Reference
Perjury and False Statements (18 USC 1001, 1621) — The Law Mind Criminal Law Encyclopedia
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