What Happens If Impeachment Evidence Are Not Disclosed ?
Failure to disclose impeachment evidence will only result in a constitutional violation if there is a reasonable probability that, had the evidence been disclosed to the defense, the result of the proceeding would have been different. See id.
A "reasonable probability" is a probability sufficient to undermine confidence in the outcome of the trial. See Kimes, 872 S.W.2d at 702.
Thus, a due process violation has occurred if:
(1) the prosecutor failed to disclose evidence;
(2) the evidence is favorable to the defendant;
(3) the evidence is material. See id.
However, the duty to turn over all material, exculpatory evidence does not create a duty to turn over evidence that would be inadmissible at trial. See Lagrone v. State, 942 S.W.2d 602 (Tex. Crim. App.), cert. denied, 522 U.S. 917, 118 S. Ct. 305, 139 L. Ed. 2d 235 (1997).
Thus, specific instances of the conduct of a witness, for the purpose of attacking or supporting the witness' credibility, other than conviction of a crime as provided in Rule 609, may not be inquired into on cross-examination nor proved by extrinsic evidence. See TEX. R. EVID. 608(b).