The perjury exception to the First Amendment 

There are many types of lies a person could tell and not get into legal trouble, and for good reason. Outside of a few narrow and formally recognized categories of unprotected speech, the First Amendment is neutral regarding the content of the speech it defends, even if that speech is dishonest or deceptive. However, when a falsehood prevents or disrupts official government action — especially if it would end up infringing upon the rights of others — then that speech is not protected by the First Amendment. A major example is when a person provides false information under oath — such as lying in their court testimony or in a deposition. This is called “perjury,” and it’s not protected by the First Amendment because false testimony may result in an unjust outcome, affecting the life and liberty of an innocent person. 

As the U.S. Supreme Court declared in United States v. Dunnigan (1993), to “uphold the integrity of our trial system . . . the constitutionality of perjury statutes is unquestioned.” 

What is perjury under U.S. law?

There are several federal anti-perjury statutes, and each state has its own. Generally, these laws prohibit intentionally or knowingly making a false statement under oath about a material matter, often under pain of imprisonment. For example, the primary federal anti-perjury law — 18 U.S.C. § 621 — criminalizes providing false testimony under oath and provides for a penalty of up to five years incarceration. 

Perjury generally consists of four key requirements: (1) a false statement; (2) the statement was made under oath; (3) intent; and (4) materiality. A false statement made under oath includes court testimony, statements made during a deposition or grand jury investigation, or a signed affidavit. Importantly, however, to constitute perjury, the defendant must knowingly intend to make a false statement; it cannot simply be an innocent mistake. Finally, the statement must relate to some important (or “material”) matter in the litigation, not a minor detail. For example, a false statement about conduct related to an alleged crime is important and could form the basis of a perjury charge. However, a false statement about a minor background fact may be too insignificant to warrant a perjury charge.

Those facing perjury charges often attempt to argue that one of these required elements was not met. For example, defendants may try to argue that they genuinely believed the allegedly perjurious statement to be true, to defeat the intent requirement. And if the answer a witness gives is literally true — even if nonresponsive or misleading — a prosecution for perjury cannot stand. As the Court explained in Bronston v. United States (1973), if a “witness evades, it is the lawyer’s responsibility to recognize the evasion and to bring the witness back to the mark, to flush out the whole truth with the tools of adversary examination.”

A person facing perjury charges may also argue that the allegedly false statement was not material to the outcome of the case. Some states, like Florida, allow perjury defendants to assert the defense of recantation — or “taking what they said back,” but only if the defendant admits that the alleged statement was false and the court determines the false statement “has not substantially affected the proceedings.” 

Together, these defenses underscore the narrow and highly fact-specific nature of perjury prosecutions and demonstrate that not every inaccurate statement made under oath will rise to the level of criminal perjury. 

When does testimony rise to the level of perjury? 

Keep in mind that not all false statements are punishable under the law, and that many types of lies are protected under the First Amendment. The Supreme Court refused to declare false speech in general an unprotected category of speech in United States v. Alvarez (2012), a case involving a challenge to the Stolen Valor Act, which criminalized false statements about receiving military honors. The Court explained that it “has never endorsed the categorical rule the Government advances: that false statements receive no First Amendment protection.” Instead, the Court found that some lies or falsehoods simply don’t cause nearly the same level of harm or problems as others. 

Furthermore, the Court declared in New York Times Co. v. Sullivan (1964) that sometimes false statements contribute to the development of ideas and are “inevitable in free debate.” As the Court explained in the majority opinion written by Justice William J. Brennan, not every false statement about a public official constitutes defamation — that only those statements uttered by a defendant with knowing falsity or “reckless disregard for the truth” rise to the level of what the Court termed the “actual malice” standard sufficient to impose liability. 

Perjury, however, is an entirely different animal from exaggerations or false statements in free debate. As the Court explained in Alvarez, “perjured statements lack First Amendment protection not simply because they are false, but because perjury undermines the function and province of the law and threatens the integrity of judgments.” The Court elaborated that “sworn testimony is quite distinct from lies not spoken under oath and simply intended to puff up oneself.”

Courts cannot adjudicate rights, crimes, contracts, or constitutional claims if the evidence itself becomes systematically unreliable. As Professors Alan Chen and Justin Marceau explained in their law review article High Value Lies, Ugly Truths, and the First Amendment, perjury “obscures, rather than leads to, truth finding. Indeed, judicial proceedings are designed to smoke out the truth and resolve disputes; lies that distort or impair the judicial process are undoubtedly harmful to these goals.” 

Decisions are based on factual records, and sworn testimony is evidence. If witnesses can knowingly lie without consequence, the evidentiary system breaks down. For this reason, perjury is a distinct category of false speech that is not protected by the First Amendment.