State witness competence rules apply in federal civil actions with respect to elements of claims or defenses for which state substantive law supplies the rule of decision.

LNC Invs. v. First Fid. Bank, 126 F. Supp. 2d 78, pin? (S.D.N.Y. 2001) ("A recent statement of the rule appears in Paolitto v. John Brown E.&C., Inc., 151 F.3d 60, 66 (2d Cir. 1998): '"Opening the door" to evidence that has been previously excluded gives the trial court...The doctrine of curative admissibility does not apply if inadmissible evidence was not initially used by an opponent.

Cf. United States v. Alvarez, 266 F.3d 587, 592-593 (6th Cir. 2001) (upholding trial court's exclusion of the tape recorded statements under Federal Rule of Evidence 804(b)(3) because the statements were not sufficiently....Federal Rule of Evidence of Evidence 804(b)(3) or a comparable State rule creates a hearsay exception for a statement which was at the time of its making so far contrary to the declarant's pecuniary or proprietary interest, or so far tended to subject the declarant to civil or criminal liability, or to render invalid a claim by the declarant against another, that a reasonable person in the declarant's position would not have made the statement unless believing it to be true. A statement tending to expose the declarant to criminal liability and offered to exculpate the accused is not admissible unless corroborating circumstances clearly indicate the trustworthiness of the statement.

United States v. Sonntag, 684 F.2d 781, 787-788 (11th Cir. 1982) (upholding trial court's admission of evidence pertaining to accused Nicholson's prior drug sale to an informant because such evidence was offered to prove accused's predisposition after he had raised the entrapment defense).A subjective entrapment defense makes an accused's criminal liability contingent on a finding of the accused's predisposition or the accused's lack of predisposition to commit the crime charged and since criminal predisposition is a character trait, the defense of subjective entrapment makes accused's character an element of either a defense or a criminal charge, evidence of accused's criminal predisposition -- including evidence in the form of reputation, opinion, and evidence of specific instances of accused's conduct -- is not barred by the rule against the use of a person's character to show the person's conduct.