“Under penalty of perjury” is a common phrase to anyone who has ever watched a courtroom drama. Perjury is the crime of intentionally lying or misrepresenting the truth to a court or government organization. There are many instances in which statements are made under penalty of perjury, including some that have nothing to do with a courtroom. Understanding the basics of perjury law can help clarify how, and when, this law may apply.
Not all regions have perjury laws; the United States and the United Kingdom both have strict federal laws prohibiting lying under oath or in a sworn statement. Other regions, such as France, do not administer oaths to suspects, so there is no crime of perjury. Generally, any legal system that requires the use of truth oaths or sworn statements may have a law against lying.
If a statement, document, or other form of testimony is under penalty of perjury, it means it is a situation in which the laws of perjury apply. Anyone giving a deposition, testifying as a witness, primary party, or expert in a court case may be required to give an oath not to commit perjury. Some experts suggest the idea works better as a threat than as an actual occurrence. There are very few cases of perjury prosecution in the legal world, mostly because of the difficulty in proving that a person was intentionally and knowingly lying rather than mistakenly giving incorrect information.
Not all untruths, even if intentional, may be considered perjury. Generally, the lie must be shown to have materially impacted the outcome of a legal case; for instance, if a witness lies by saying she saw a particular person shoot a victim, and this evidence is used to convict the accused, the witness could be charged with perjury if the truth comes out. If, however, she lies about her weight, this would likely not be grounds for a perjury charge, as it probably had no material impact on the judge or jury.
In addition to court-related proceedings, some other legal documents are signed under penalty of perjury. Income tax documents, for instance, generally include a sworn signature that verifies that the information given is true and accurate to the best of the preparer's knowledge. In the United States, violating tax-related perjury laws can result in a hefty fine and up to three years in prison. In most cases, a statement or document that is bound by perjury laws will say so.