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Perjury, also known as false oath, forswearing, and falsehood, refers to knowingly making a false statement under oath or knowingly signing a legal document that is false or includes false statements. While the exact definition of perjury varies from jurisdiction to jurisdiction, a witness in a trial commits perjury when they knowingly and intentionally lie about a material issue. 

The false statements must contain a material fact that substantially affects the adjudication (procedure or the outcome) of the proceeding. In addition, the false or misleading statement must be a deliberate and voluntarily made statement by the person charged with perjury. The Supreme Court has ruled that a merely unresponsive or evasive testimony containing the literal truth cannot be a basis for a perjury conviction, even if the declarant calculated to make the statement misleading. Note that the oath or the affirmation of the veracity of the false statement made is the specific act that constitutes perjury and not simply making the false statement itself (see: Bronston v. United States, 409 U.S. 352 (1973)). 

An intentionally omitted statement or promise under oath could also qualify as perjury. While not all false statements equate to perjury, if the false statement does not amount to a material fact, or if the declarant did not make the statement under oath, then generally, the lie (intentional or not) does not amount to perjury. The 5th Amendment of the U.S. Constitution forbids a citizen from self-incrimination; therefore, a defendant or a witness may invoke the 5th Amendment protection and refuse to answer a certain question.

The elements of perjury include: 

  • The existence of the declarant’s oath to testify the truth, 
  • The willful presentation of the false statement despite the taking of the oath, 
  • The declarant’s knowledge of the falsity of the statement, and 
  • The materiality of the statement. 

The declarant must have the actus reus (the commission of the act by the declarant) and the mens rea (the intention to make such false statements) for a perjury conviction. For instance, the federal statute requires the declarant to act “willfully,” and the Ohio statute requires the declarant to act “knowingly.” Nevertheless, a factually correct statement made by the declarant cannot incriminate the declarant under perjury. Moreover, stating a false statement about facts or issues outside the legal proceeding does not constitute perjury. A statement that is a personal interpretation of a fact does not amount to perjury because the interpretation of an individual generally jumps to a conclusion with incorrect assumptions or honest mistakes. For example, the declarants may argue that they made an honest mistake when they believed the statement to be true, thus not having the requisite mens rea for perjury.

To defend against possible perjury, the defense counsel could prove that the defendant mistakenly believed the statement to be true even though the statement may be false. Also, the defense counsel could present evidence that the defendant’s statement did not amount to a material fact of the proceeding. The defense counsel may even present evidence that the defendant promptly addressed the false statement by recanting the false statement as proof of having no intent to mislead. The declarant must make the recantation before the statement is proven false. Also, the false statement must not have affected the proceeding materially. The defense counsel could commit a subordination of perjury, which occurs when the defense counsel advises or persuades a declarant to commit perjury. Finally, mistakenly believing that the false statement is not material is not a valid defense.

In determining perjury, deciding whether the statement at issue during the proceeding is considered material is crucial. For instance, the Supreme Court has defined the materiality of the statement as tending to influence the decision-maker's decision process in determining the outcome of the proceeding (see: Kungys v. United States, 485 U.S. 759 (1988)). 

Federal law classifies perjury as a crime under the general perjury statute, which is punishable by a fine or up to five years in prison. 18 U.S.C. §§ 1621 and 1623 forbids perjury and other false declarations within federal courts.

See also: Dunn v. U.S. 442 U.S. 100 (1979) and State Civil Procedure Statutes.

[Last updated in January of 2024 by the Wex Definitions Team]