Relevant evidence is admissible unless another rule of evidence, law, or valid principle mandates or permits exclusion.

Mu?oz v. State Farm Lloyds of Texas, 522 F.3d 568, 573 (5th Cir. 2008) (civil action to recover damages under fire insurance policy; at trial evidence was admitted that one insured failed polygraph test; arson was suspected; "The Mu?ozes' first argument fails because 'this Court has denounced the per se...There is scattered federal authority that polygraph test results are admissible under some circumstances on the issue of the truthfulness or untruthfulness of a witness.

Jerden v. Amstutz, 430 F.3d 1231, 1239 (9th Cir. 2005) (holding, in plaintiff spouses' action against defendant neurosurgeon for medical negligence, that the testimony of defendant's surgical assistant about the....The doctrine of curative admissibility does not apply if inadmissible evidence was not initially used by an opponent.

United States v. Seymour, 468 F.3d 378, 386-387 (6th Cir. 2006) (holding that evidence of victim's specific instances of conduct was inadmissible where such character was not an essential element of the charge against the defendant).When an exception makes the victim's character admissible, the testimony of a witness on direct examination about the victim's character must take the form of opinion or reputation and it cannot take the form of specific instances of victim's conduct.