A statement qualifies as a statement against interest for purposes of the hearsay exception for statements against interest only if the statement, at the time the declarant made it, was so contrary to the declarant's interest that a reasonable person in the declarant's position would not have made if the declarant had believed the statement to be untrue.

Love v. National Medical Enterprises, 230 F.3d 765, 776 (5th Cir. 2000) (holding, in plaintiff health insurer's action against defendant hospitals for recovery of payments made for fraudulent insurance claims, that there was....A thing or matter is sufficiently authenticated to be admissible in evidence if the authenticating evidence submitted to the trial court is sufficient -- strong enough -- to permit a reasonable jury or reasonable trier of fact to conclude that the proffered thing or matter is authentic, that the proffered thing or matter is what its proponent claims it is.

Fed. R. Evid. 403.Evidence of untruthfulness may be excluded as unduly prejudicial under the standards laid down in rules such as the federal "undue prejudice" rule codified by Federal Rule of Evidence 403. However, if specific rules governing impeachment call for the use of different prejudice standards, the standards set forth in those specific rules govern rather than the standards set forth in a general undue prejudice rule such as Federal Rule of Evidence 403.

Herman v. City of Allentown, 985 F. Supp. 569, 577 (E.D. Pa. 1997) (holding, in plaintiff firefighter's action against defendant city for discrimination, that evidence of the settlement agreement was admissible because it was....Although settlement negotiations and offers are inadmissible (i) to show the validity or invalidity of a claim when validity is in dispute, (ii) to show the amount of damages when the amount is in dispute, or (iii) to impeach by showing a prior inconsistent statement or specific contradiction, evidence about settlements and settlement offers and negotiations in civil actions is admissible for a wide variety of purposes; such settlement evidence is admissible whenever it is not offered on a disputed question of the validity of a claim or its amount or to impeach a witness with a prior inconsistent statement or by specific contradiction.