At common law, a willfully false statement in a fact material to the issue, made by a witness under oath in a competent judicial proceeding. By statute the penalties of perjury are imposed on the making of willfully false affirmations.
Lying under oath,” or “perjury” is a criminal offense. A person is legally required to truthfully answer questions, or abstain from answering at all, if he or she has sworn before a court clerk, notary public, or other official to tell the truth. Perjury interferes with a juror, judge, or official's ability to accurately understand the information being presented.