If a person testifies falsely after taking the oath, or writes a false statement on a document supported by affidavit, he can be prosecuted for perjury. The act is a criminal offense where the person knew the testimony or statement was false.
The states have their own laws on perjury when the offense takes place in state court or in relation to a state agency. For example, in Illinois, perjury is a Class 3 felony offense punishable by 2-5 years in the Illinois Department of Corrections. See 720 ILCS 5/32-2.
Untrue testimony or falsely sworn documents relating to a federal court or administrative agency can result in federal perjury charges. The penalty for a federal offense is almost always more severe than the sentence for a similar state law offense.
The federal perjury statute is 18 USC 1621. The elements of perjury are the following:
- A false statement.
- On a material issue.
- Made willfully and with knowledge that it was false.
- Under oath (by someone authorized to administer the oath).
- Before an authorized tribunal, officer, or person.
See 18 USC 1621.
A material issue is something that, in one way or another, determines the outcome of a legal proceeding. If the false statement would not or could not change the final disposition of a legal proceeding, then it is arguably immaterial and not a basis for perjury charges.
The sentence for this charge is a maximum of 5 years in prison.
These federal statutes apply to witness testimony and written statements made on legal documents (eg, motions, pleadings, affidavits, etc). A document that contains an affidavit, verification, certification, sworn declaration, or oath can be the basis of a perjury charge.
Where the United States Attorney provides immunity to a witness in the prosecution of another, the immunity does not excuse perjury. The federal statute on witness immunity, 18 USC 6002, says immunity does not apply to
a prosecution for perjury, giving a false statement, or otherwise failing to comply with the order.