Robert Wilkerson appeals the denial of his second habeas corpus petition brought under 28 U.S.C. § 2254. For the reasons assigned, we vacate the decision of the district court and remand for further proceedings consistent herewith.
BACKGROUND
In 1973, while an inmate at Louisiana State Penitentiary at Angola, Wilkerson and fellow inmate Grady Brewer were convicted of the second-degree murder of inmate August Kelly, who was stabbed to death in a prison fight. On appeal, the *888Louisiana Supreme Court vacated Wilkerson’s conviction, holding that the trial “court abused its discretion in requiring Wilkerson to appear before the jury handcuffed, shackled, and with his mouth taped.1 On retrial, Wilkerson was convicted and received a sentence of life imprisonment.
The state’s only evidence that Wilkerson committed the crime was the eyewitness testimony of inmate William Riley who testified at both trials that he was standing within four to five feet of the altercation and witnessed Wilkerson stab Kelly. There was no physical evidence linking Wilkerson to the murder. Although eight knives were seized from prisoners, the knife used to inflict the fatal wounds was never discovered. No fingerprints were found; no blood samples were taken. Wilkerson’s conviction was affirmed on direct appeal.2
After exhausting his state remedies, Wilkerson filed a federal habeas petition under 28 U.S.C. § 2254 asserting that: (1) women were excluded from the grand jury venire in violation of the Constitution; (2) an individual member of the grand jury should have been excluded on the grounds of improper domicile; (3) he was denied an adequate opportunity to cross-examine Riley; (4) he was wrongly handcuffed and shackled at his second trial; and (5) counsel was ineffective for failing to reargue a previously denied motion to quash the indictment based on the exclusion of women from the grand jury venire, failing to move to quash the indictment based on the allegedly unqualified grand juror, and failing to object when he was handcuffed and shackled at the second trial.3 Bound by
precedent, the panel granted habeas relief on the grand jury composition claim, but requested the court to reconsider the issue en banc. Wilkerson’s other constitutional challenges were rejected as without merit.4 On rehearing, the en banc court reversed the panel’s decision based on Daniel v. Louisiana,5 which held that Taylor v. Louisiana6 did not apply retroactively to convictions obtained by juries empaneled prior to Taylor’s effective date. Thus, Taylor’s holding, that Louisiana’s constitutional provision allowing women to be exempt from petit jury service violated the Constitution, did not affect the validity of Wilkerson’s conviction. The en banc court reinstated the panel’s opinion in all other respects, and the Supreme Court denied certiorari.7
In August 1995, Wilkerson filed the instant habeas petition in the district court in which he raised three issues that were rejected in his prior § 2254 petition: grand jury composition; shackling; and limitation on cross-examination. Wilkerson also raised a new ineffective assistance of counsel claim, alleging that counsel was ineffective for failing to call John Baugh as a defense witness at the second trial. Baugh was one of the prison guards working on the tier the morning of the murder and had released the inmates from their cells to the showers. He testified at the first trial for the prosecution. This ineffective assistance claim was not raised in any prior habeas petition, although Wilkerson concedes knowledge of the facts relative to the claim were known to him when those petitions were filed.
*889The petition was referred to a magistrate judge who recommended that the writ be denied. Adopting the responsive report and recommendation, the district court rejected all of Wilkerson’s constitutional claims and denied him a Certificate of Probable Cause. On appeal to this Court, Wilkerson’s request for a CPC initially was denied. That order, however, was vacated and a CPC subsequently was granted.
ANALYSIS
Ordinarily, under Rule 9(b) of the rules governing federal habeas corpus petitions, a federal court will not entertain a successive or otherwise abusive petition.8 An exception exists if a petitioner can prove that he is “actually innocent” of the crime of conviction.9 That is, if a petitioner can establish, through new evidence not previously available, that “it is more likely than not that no reasonable juror would have convicted him in light of the new evidence,”10 a federal court may consider otherwise barred constitutional claims in order to avoid a “fundamental miscarriage of justice.”11 Reconsideration of constitutional challenges rejected on the merits by a previous federal court is reserved for only exceptional cases because, as noted in Schlwp, a substantial showing of actual innocence is extremely rare.12 To justify granting the writ a habeas petitioner must also show that an independent constitutional violation occurred at the trial that probably resulted in his conviction.13
Wilkerson’s new evidence consists of the following. On June 16,1988, William Riley executed an affidavit in which he recanted his testimony and stated that he did not witness the killing but, rather, merely related to prison officials what another inmate had told him. Similarly, inmate Charles Lawrence, who testified at the first trial but not the second, executed two affidavits in which he recanted his testimony. In the first, dated April 19, 1988, Lawrence avers that his testimony “should not have been considered credible” because he was coerced into testifying on behalf of the state. He stated that prison officials threatened to indict him for Kelly’s murder and would revoke his pending release date if he did not testify. In his affidavit dated July 27, 1995, Lawrence repeated the statements from his first affidavit and added that he knew Wilkerson had no part in the killing because he was standing next to Wilkerson when the offense was committed. In 1997 Grady Brewer, Wilkerson’s codefendant, executed an affidavit admitting sole responsibility for Kelly’s death. At the second trial Brewer testified that he stabbed Kelly in the chest and back, but he did not say that Wilkerson was not involved.
In reviewing the instant petition the district court did not conduct an evidentiary hearing to determine the reliability of these affidavits. Like the magistrate *890judge, the court assumed that Wilkerson had met the requisite showing of actual innocence and it then considered his four allegations of constitutional error. Each was rejected. Accordingly, for present purposes, we now assume the validity of these affidavits and address each of Wilkerson’s claims. Because this habeas petition was filed in 1995, prior to the enactment of the Antiterrorism and Effective Death Penalty Act of 1996, we apply the law as it existed prior to the AEDPA’s effective date.14 We review the district court’s conclusions of law de novo, and will uphold its findings of fact unless they are clearly erroneous.15 A state court’s determination of a factual issue is presumed to be correct and will be upheld unless, among other things, it is not fairly supported by the record as a whole.16
Wilkerson contends that the trial court violated his rights under the Confrontation Clause by unduly restricting defense counsel’s cross-examination of Riley, the purported eyewitness to the crime. More specifically, defense counsel was not permitted to question Riley about letters he had written to prison administrators prior to Wilkerson’s first trial concerning a transfer request and his decision to testify for the state.17 The trial court limited the scope of counsel’s questioning to whether Riley had received anything of value in exchange for his testimony.
Whether the trial court violated Wilkerson’s rights under the sixth and fourteenth amendments is a mixed question of law and fact that we review de novo.18 Habeas relief may be granted based on the state court’s erroneous evidentiary ruling only if that ruling violated Wilkerson’s constitutional rights or rendered his trial fundamentally unfair.19 “Cross-examination is the principal means by which the believability of a witness and the truth of this testimony are tested.”20 Although the scope of cross-examination is within the discretion of the trial court and, as such, it may impose reasonable limits on defense counsel’s inquiry, “that discretionary authority comes about only after sufficient cross examination has been granted to satisfy the Sixth Amendment.”21
The trial court held that the letters and circumstances surrounding Riley’s transfer had no bearing on his credibility as a witness. We disagree. It is axiomatic that defense counsel should be permitted to expose to the jury facts relative to a witness’ possible motivation to testify favorably for the prosecution or his potential bias for or against any party to the criminal proceeding.22 Such information is “always relevant as discrediting the witness and affecting the weight of his testimony.” 23 In the instant case, it is undisputed that in the subject letters Riley requested a transfer, one which he ultimately received. That transfer may not have been part of a “deal” with the state but, as we *891have stated previously, “[w]hat tells, of course, is not the actual existence of a deal but the witness’ belief or disbelief that a deal exists.”24 Further, the imperative of protecting a defendant’s right to effective cross-examination is. even more critical where, as here, the witness is crucial to the prosecution’s case.25
Although the defense was able to challenge Riley’s credibility in general,26 we are not persuaded that Wilkerson was afforded an adequate opportunity to cross-examine him on the issue of his credibility tightly focused on his veracity in the instant trial.27 While defense counsel was allowed to inquire whether Riley actually received anything in exchange for his testimony, “counsel was unable to make a record from which to argue why [Riley] might have been biased or otherwise lacked that degree of impartiality expected of a witness at trial.”28 Even more critical, because of the limited extent of cross-examination permitted, the jury may well have inferred that defense counsel merely was “engaged in a speculative and baseless line of attack” on Riley’s credibility.29
The state insists that inquiry into the letters and subsequent transfer would have unduly prejudiced the defense because the jury would have learned that Wilkerson previously was convicted of Kelly’s murder, and could have inferred that Riley was seeking a transfer to get away from Wilkerson. We reject this contention for two reasons. First, the jury already was aware that Wilkerson had gone to trial for Kelly’s murder and that the verdict had been reversed on appeal. During voir dire, when questioned about whether he had heard anything about the case, one potential juror responded that he understood that the case had been to the state Court of Appeal and had been referred back for retrial. This statement was made in open court in the presence of the other potential and empaneled jurors. Second, on cross-examination Riley admitted that in October 1973, around the time of Wilkerson’s first trial, he told his family that he feared for his life because one of the prison guards told another inmate to “get him.” Thus, the jury could have inferred that Riley was afraid, not of Wilkerson, but of this other inmate and prison guard. Regardless, it was within the exclusive province of the jury to make this determination.30 Clearly, the jury was denied information essential to its assessment of Riley’s believability and, in turn, of the strength of the state’s case against the defendant. We must conclude that the trial court deprived Wilkerson of his sixth amendment right to confront fully the witnesses against him.
*892Having reached this conclusion, we must determine whether the error was harmless. Resolution of this inquiry turns on whether the constitutional violation “had substantial and injurious effect or influence in determining the jury’s verdict.” 31 Under this standard, a petitioner may obtain habeas relief only if there is “more than a mere reasonable possibility that [the error] contributed to the verdict.” 32 As emphasized above, the prosecution’s case hinged on Riley’s supposed eyewitness account of Kelly’s murder. There was no other evidence, physical or otherwise, that connected Wilkerson to the crime. Had the jury believed that Riley was testifying to curry favor with the state, or that he expected some" real or perceived benefit in return, the state’s case would have been seriously undermined. Accordingly, it is apparent that there is more than a reasonable possibility that the verdict may have been different had defense counsel been permitted to inquire fully into these matters. We therefore must conclude that this constitutional error, in this setting, would warrant the grant of habeas relief.33
Wilkerson next contends that he was denied a fair trial because the indicting grand jury systematically excluded women, and because he and the defense witnesses were forced to appear before the jury handcuffed and shackled. Wilkerson is not entitled to habeas relief on these issues for the reasons as set forth in this court’s prior opinions.34
Finally, Wilkerson complains that defense counsel was ineffective for failing to call prison guard Baugh as a defense witness in the second trial.35 Wilkerson contends that if Baugh had testified substantially as he did in the first trial, the defense would have shown that: (1) Baugh could not identify Wilkerson as having been involved in the murder; (2) Riley had a motive to testify for the prosecution because he was the only inmate on the tier who was not charged with Kelly’s murder; and (3) Baugh’s account of the events and, specifically, of Wilkerson’s and Brewer’s behavior, was inconsistent with Riley’s testimony.
To prevail on an ineffective assistance of counsel claim, the defendant must prove that counsel’s performance was both deficient and that the deficiencies were so prejudicial that, but for the errors, there is a reasonable probability that the result would have been different.36 Counsel is entitled to a presumption that his performance was adequate and “complaints of uncalled witnesses are not favored, because the presentation of testimonial evi*893dence is a matter of trial strategy.”37
At Wilkerson’s first trial, Baugh testified that he released eleven inmates from their cells to go to the showers, including Kelly, Wilkerson, Brewer, and Riley. The inmates congregated at the back of the tier for a meeting and Baugh overheard inmate Abraham Thompson arguing with Wilkerson. He also heard Wilkerson tell Thompson that he “didn’t know anything about it” and that Thompson should ask Kelly. Thompson then started talking to Kelly. A few minutes later, Baugh noticed that Brewer was acting “like he wanted to fight with somebody,” but then he “quitened [sic] down.” A fight began shortly thereafter. There was a “big crowd ... in the corner” and it looked like three to five unidentified inmates were fighting. The inmates initially ignored Baugh’s instructions to stop fighting, but they eventually returned to their cells, leaving Kelly dying on the floor. When asked about the whereabouts of Riley and Lawrence, Baugh replied that all of the inmates were at the end of the tier where the fight occurred. He also testified that he did not see anyone using a weapon. Our review of the record persuades that defense counsel was not ineffective for failing to call Baugh as a defense witness in the second trial.
For these reasons, we VACATE the decision of the district court and REMAND for further proceedings consistent herewith including, but not necessarily limited to, a determination of the reliability of certain affidavits that heretofore has been assumed.
. State v. Brewer, 301 So.2d 630 (La.1974). These restraints were imposed due to an unseemly outburst by Brewer.
. State v. Wilkerson, 326 So.2d 353 (La.1976).
. Wilkerson v. Whitley, 16 F.3d 64 (5th Cir. 1994).
. Id. at 66-68.
. 420 U.S. 31, 95 S.Ct. 704, 42 L.Ed.2d 790 (1975).
. 419 U.S. 522, 95 S.Ct. 692, 42 L.Ed.2d 690 (1975).
. Wilkerson v. Whitley, 28 F.3d 498 (5th Cir. 1994) (en banc), cert. denied, 513 U.S. 1085, 115 S.Ct. 740, 130 L.Ed.2d 642, and reh’g denied, 513 U.S. 1199, 115 S.Ct. 1272, 131 L.Ed.2d 149 (1995).
.Rule 9(b) provides:
A second or successive petition may be dismissed if the judge finds that it fails to allege new or different grounds for relief and the prior determination was on the merits or, if new and different grounds are alleged, the judge finds that the failure of the petitioner to assert those grounds in a prior petition constituted an abuse of the writ.
28 U.S.C. foil. § 2254.
Wilkerson’s petition is both successive and abusive. As noted, his first three constitutional challenges were reviewed and rejected on the merits by this court and the fourth claim could have been raised in his prior petitions. See Kuhlmann v. Wilson, 477 U.S. 436, 444 n. 6, 106 S.Ct. 2616, 91 L.3d.2d 364 (1986) (acknowledging the distinction between the two terms).
. Schlup v. Delo, 513 U.S. 298, 115 S.Ct. 851, 130 L.Ed.2d 808 (1995).
. Id. at 327, 115 S.Ct. 851.
. Id. at 321, 115 S.Ct. 851.
. Id. at 321-22, 115 S.Ct. 851.
. Id. at 327, 115 S.Ct. 851; Murray v. Carrier, 477 U.S. 478, 496, 106 S.Ct. 2639, 91 L.Ed.2d 397 (1986).
. Lindh v. Murphy, 521 U.S. 320, 117 S.Ct. 2059, 138 L.Ed.2d 481 (1997); Gochicoa v. Johnson, 118 F.3d 440 (5th Cir.1997).
. Fairman v. Anderson, 188 F.3d 635 (5th Cir. 1999).
. 28 U.S.C. § 2254(d); Sumner v. Mata, 455 U.S. 591, 102 S.Ct. 1303, 71 L.Ed.2d 480 (1982).
. Riley testified that he was transferred in either September or October of 1973, after Wilkerson's first trial. Riley also stated, outside the presence of the jury, that he was transferred in July 1973, before the first trial.
. Gochicoa, 118 F.3d at 445.
. Johnson v. Puckett, 176 F.3d 809 (5th Cir. 1999).
. Davis v. Alaska, 415 U.S. 308, 316, 94 S.Ct. 1105, 39 L.Ed.2d 347 (1974).
. United States v. Landerman, 109 F.3d 1053, 1061 (5th Cir.1997) (citing United States v. Restivo, 8 F.3d 274 (5th Cir. 1993)).
. Delaware v. Van Arsdall, 475 U.S. 673, 106 S.Ct. 1431, 89 L.Ed.2d 674 (1986); Davis, 415 U.S. at 316-17, 94 S.Ct. 1105.
. Landerman, 109 F.3d at 1062 (quoting Davis, 415 U.S. at 316, 94 S.Ct. 1105).
. United States v. Hall, 653 F.2d 1002, 1008 (5th Cir. 1981) (quoting United States v. Onori, 535 F.2d 938, 945 (5th Cir. 1976)).
. United States v. Mizell, 88 F.3d 288 (5th Cir.1996); United States v. Cooks, 52 F.3d 101 (5th Cir. 1995).
. Defense counsel was able to establish that Riley was dishonorably discharged from the Marines and, through defense witnesses, that he had a reputation at the penitentiary for being untruthful. In addition, the juiy obviously was aware that Riley was an inmate at Angola, and he admitted that he was serving time for armed robbery.
. Davis, 415 U.S. at 316, 94 S.Ct. 1105 (“A more particular attack on the witness' credibility is effected by means of cross-examination directed toward revealing possible biases, prejudices, or ulterior motives of the witness as they may relate directly to issues or personalities in the case at hand.”).
. Davis, 415 U.S. at 318, 94 S.Ct. 1105.
. Id.
. Riley's admission that he feared he would be killed by someone on the tier, other than Wilkerson, when coupled with the numerous letters he wrote to prison administration requesting a transfer, is even stronger evidence that inquiry into these matters should have been permitted. Indeed, Riley had "considerable incentive ... to ‘slant, unconsciously or otherwise, his testimony in favor of or against a party.' " United States v. Cooks, 52 F.3d at 104 (quoting United States v. Abel, 469 U.S. 45, 52, 105 S.Ct. 465, 83 L.Ed.2d 450 (1984)).
. Brecht v. Abrahamson, 507 U.S. 619, 637, 113 S.Ct. 1710, 123 L.Ed.2d 353 (1993) (holding that harmless error standard announced in Kotteakos v. United States, 328 U.S. 750, 66 S.Ct. 1239, 90 L.Ed. 1557 (1946), applied to habeas review of constitutional claims). See also California v. Roy, 519 U.S. 2, 117 S.Ct. 337, 136 L.Ed.2d 266 (1996), and O’Neal v. McAninch, 513 U.S. 432, 115 S.Ct. 992, 130 L.Ed.2d 947 (1995).
. Woods v. Johnson, 75 F.3d 1017, 1026 (5th Cir.1996) (emphasis omitted).
. Schlup, 513 U.S. at 327, 115 S.Ct. 851.
. Wilkerson v. Whitley, 28 F.3d 498 (en banc); 16 F.3d 64 (5th Cir.1994).
. As stated earlier, Wilkerson did not raise this claim of ineffective assistance in any of his previous state or federal petitions, although he certainly could have. The magistrate and district court concluded, however, that Wilkerson had exhausted his state remedies with respect to this claim because it was merely a variation on the previous ineffective assistance claims that had been raised and rejected. Regardless, even if Wilkerson has failed to exhaust his state remedies, because exhaustion is not jurisdictional, under pre-AEDPA law we retain the discretion to reach the merits of the petition "to avoid unnecessary delay in granting relief that is plainly warranted.” Granberry v. Greer, 481 U.S. 129, 135, 107 S.Ct. 1671, 95 L.Ed.2d 119 (1987); Graham v. Johnson, 94 F.3d 958 (5th Cir.1996).
.Strickland v. Washington, 466 U.S. 668, 104 S.Ct. 2052, 80 L.Ed.2d 674 (1984).
. United States v. Cockrell, 720 F.2d 1423, 1427 (5th Cir.1983) (internal quotations and citations omitted).