A willful act or declaration contrary to truth. It is committed either by the willful act of the party, by dissimulation, or by words. It's willful for example, when the owner of a thing sells it twice by different contracts to different individuals, unknown to them; for in this the seller must willfully declare the thing is his own when he knows that it is not so. It is committed by dissimulation when a creditor, having an understanding with his former debtor, sells the land of the latter although he has been paid the debt which was due to him.
perjury - is committed when a witness swears to what he knows not to be true.
It is a general rule that if a witness testifies falsely as to any material fact the whole of his testimony may be rejected, but still the jury may consider whether the wrong statement is of such character as to entitle the witness to be believed in other respects.
To alter or make false a thing or record. This is punishable at common law.
'If any person shall feloniously steal, take away, alter, falsify, or otherwise avoid, any record, writ, process, or other proceedings in any of the courts of the United States, by means whereof any judgment shall be reversed, made void, or not take effect; or if any person shall acknowledge, or procure to be acknowledged, in any of the courts. aforesaid, any recognizance, bail, or judgment, in the name or names of any other person or persons not privy or consenting to the same, every such person, or persons, on conviction thereof, shall be fined not exceeding five thousand dollars, or be imprisoned not exceeding seven years, and be whipped not exceeding thirty-nine stripes'. Provided nevertheless, that this act shall not extend to the acknowledgment of any judgment or judgments by any attorney or attorneys, duly admitted, for any person or persons against whom any such judgment or judgments shall be had or given.' - Act of Congress, 1790
Chancery Practice. When a bill to open an account has been filed, the plaintiff is sometimes allowed to surcharge and falsify such account; and if any thing has been inserted that is a wrong charge, he is at liberty to show it, and that is a falsification.