Under some circumstances untruthfulness is admissible to impeach a witness.

United States v. Stephens, 549 reporter? 459, 462 (6th Cir. 2008) ("The government must provide sufficient evidence of the prior bad act so that 'the jury can reasonably conclude that the act occurred and that the defendant was the actor.' Huddleston v. United States, 485 U.S....Evidence of another crime, wrong, or act is admissible if there is sufficient evidence to support a finding by a reasonable juror that the other crime, wrong, or act occurred. Clear and convincing evidence is unnecessary; "sufficient" means only that there must be enough evidence to make the other crime, wrong, or act relevant.

Cf. United States v. $125,938.62 Proceeds of Certificates of Deposit, 537 F.3d 1287, 1292 (11th Cir. 2008) (holding, in government's civil forfeiture action involving funds stolen from the Nicaraguan treasury, that evidence of Nicaraguan President's judgment of....An exception to the hearsay rule applies to the following records of government offices and agencies: (A) public records that set forth the activities of the government office or agency; (B) public records that set forth observations that a government office or agency was required to make and report but this exception does not apply in criminal cases to observations of police officers and other law enforcement personnel; or (C) in civil actions and proceedings and in criminal cases when offered against the government, factual findings resulting from an investigation made pursuant to authority granted by law, unless the sources of information or other circumstances indicate the untrustworthiness of such findings.

United States v. Sappe, 898 F.2d 878, 879 (2d Cir. 1990) (upholding trial court's admission into evidence of accused's prior robberies where accused's modus operandi in robbing banks was distinctive, and thus probative of identity).If another crime or wrong is offered under the second sentence of Federal Rule of Evidence 404(b) to show the identity of an actor, wrongdoer, or defendant (e.g., to show that a criminal defendant rather than someone else committed the crime for which defendant is on trial), the other crime or wrong and the act, wrong, or crime at issue at trial must have been committed in a distinctive as well as similar fashion.