Perjury versus Truth-Revelation: Quantity or Quality of Testimony

In trials witnesses often slant their testimony to advance their interests. To obtain truthful testimony, courts rely on perjury rules. We show that truth-revelation is possible and that perjury rules are not truth-revealing. If the judge uses a truth-revealing mechanism, he will get little testimony because the defendant will not present a witness with unfavorable news; however, testimony is of high quality. Under perjury the court gets a different amount of testimony with lower informational content. A court striving for precision prefers truth-revelation to perjury. If the court is rational in the Bayesian sense, chances for the defendant to prevail are the same under perjury and truth-revelation from an ex ante point of view. Truth-revelation thus dominates perjury even when the different quantity of testimony is taken into account