Perjury

Perjury, also known as forswearing, is the willful act of swearing a false oath or affirmation to tell the truth, whether spoken or in writing, concerning matters material to a judicial proceeding. That is, the witness falsely promises to tell the truth about matters which affect the outcome of the case. For example, it is not considered perjury to lie about one's age unless age is a factor in determining the legal result, such as eligibility for old age retirement benefits.

Perjury is considered a serious offense as it can be used to usurp the power of the courts, resulting in miscarriages of justice. In the United States, for example, the general perjury statute under Federal law classifies perjury as a felony and provides for a prison sentence of up to five years. On the other hand, the California Penal Code allows for perjury to be a capital offense in cases causing wrongful execution. However prosecutions for perjury are rare. In some countries such as France and Italy, suspects cannot be heard under oath or affirmation and thus cannot commit perjury, regardless of what they say during their trial.

The rules for perjury also apply when a person has made a statement under penalty of perjury, even if the person has not been sworn or affirmed as a witness before an appropriate official. An example of this is the United States' income tax return, which, by law, must be signed as true and correct under penalty of perjury (see 26 U.S.C. § 6065). Federal tax law provides criminal penalties of up to three years in prison for violation of the tax return perjury statute. See: 26 U.S.C. § 7206(1)

Statements which entail an interpretation of fact are not perjury because people often draw inaccurate conclusions unwittingly, or make honest mistakes without the intent to deceive. Individuals may have honest but mistaken beliefs about certain facts, or their recollection may be inaccurate, or may have a different perception of what is the accurate way to state the truth. Like most other crimes in the common law system, to be convicted of perjury one must have had the intention (mens rea) to commit the act, and to have actually committed the act (actus reus). Further, statements that are facts cannot be considered perjury, even if they might arguably constitute an omission, and it is not perjury to lie about matters immaterial to the legal proceeding.

Subornation of perjury, attempting to induce another person to perjure themselves, is itself a crime.