Perjury is the criminal offense of making a false statement under oath—verbally or in writing—that the witness knows to be false and that is material to the proceeding in which the statement is made. And suborning perjury or subornation of perjury is the criminal offense of procuring the perjury of another person.

Perjury is a criminal offense under both state and federal laws and may be prosecuted as a misdemeanor or as a felony offense, depending on the state or federal jurisdiction, and whether there are any aggravating factors that increase the seriousness of the crime. Perjury laws are located in state statutes—often in the penal or criminal code—and the federal perjury law is located in the United States Code at 18 U.S.C. §1621.

In Montana, perjury is addressed under Montana Code Annotated (MCA) § 45-7-201. The law defines perjury as knowingly making a false statement under oath or affirmation in an official proceeding or offering a statement that one does not believe to be true. The offense is considered a felony in Montana, and the severity of the punishment can vary based on the circumstances and the impact of the false statement on the proceeding. Subornation of perjury, which involves persuading or inducing another person to commit perjury, is also a serious offense and is treated with similar gravity under Montana law. At the federal level, perjury is governed by 18 U.S.C. § 1621, which also defines the crime as willfully making false statements under oath in federal proceedings, and it can be prosecuted as a felony, with penalties including fines and imprisonment. Both state and federal laws aim to uphold the integrity of the legal system by deterring and punishing false testimony.