concurring in part and dissenting in part:
I agree with Judge Thomas that we must “reverse and remand with instructions to the district court to hold an evi-dentiary hearing on Garceau’s claim of ineffective assistance of counsel during the sentencing phase”; indeed, even “the warden conceded as much during oral argument of this case.” Supra, Concurrence at 778 (Thomas, J., concurring). But the majority goes further, reversing and remanding with instructions to grant Garceau a writ of habeas corpus (unless California grants him a new trial) based on the “other crimes” jury instruction. Because I believe that even if the instruction might have violated Garceau’s due process rights any error was harmless under the deferential standard of Brecht v. Abrahamson, 507 U.S. 619, 637, 113 S.Ct. 1710, 123 L.Ed.2d 353 (1993), I respectfully dissent.
I
The majority forthrightly admits that “the Supreme Court has never expressly held that ... it violates due process to admit other crimes evidence for other purposes without an instruction limiting the jury’s consideration of the evidence to such purposes.” Supra, Maj. Op. at 775. Nonetheless, the majority extends this court’s precedents to hold that the “other crimes” instruction given in this case, which explicitly allowed the jury to use evidence of Garceau’s other crimes as propensity evidence, “so offended fundamental conceptions of justice and fair play as to rise to the level of a constitutional violation,” id. at 775.1
*782The majority may be right on this point. Certainly, “[t]he Constitution does not encompass all traditional legal rules and customs, no matter how longstanding and widespread such practices may be.” United States v. LeMay, 260 F.3d 1018, 1024 (9th Cir.2001). And indeed, the Supreme Court has warned against the wholesale importation of common law and evidentiary rules into the Due Process Clause of the Constitution. Thus, in Dowling v. United States, the Court explained that a rule or practice must be a matter of “fundamental fairness” before it may be said to be of constitutional magnitude. 493 U.S. 342, 352, 110 S.Ct. 668, 107 L.Ed.2d 708 (1990); see also id. (“[B]eyond the specific guarantees enumerated in the Bill of Rights, the Due Process Clause has limited operation.”). But as we have pointed out before, the Supreme Court has further explained that “the primary guide for determining whether a rule is so ‘fundamental’ as to be embodied in the Constitution is historical practice.” LeMay, 260 F.3d at 1025(citing Montana v. Egelhoff, 518 U.S. 37, 43, 116 S.Ct. 2013, 135 L.Ed.2d 361 (1996) (plurality opinion)). And as we have recognized, “it seems clear that the general ban on propensity evidence has the requisite historical pedigree to qualify for constitutional status.” Id. (citing Old Chief v. United States, 519 U.S. 172, 117 S.Ct. 644, 136 L.Ed.2d 574 (1997); Michelson v. United States, 335 U.S. 469, 69 S.Ct. 213, 93 L.Ed. 168 (1948); and McKinney v. Rees, 993 F.2d 1378 (9th Cir. 1993)); see also, e.g., Harrison’s Trial, 12 How. St. Tr. 834, 864 (Old Bailey 1692) (Holt, C.J.) (excluding propensity evidence in a murder trial, remarking, “Hold, what are you doing now? Are you going to arraign his whole life? Away, away, that ought not to be; that is nothing to the matter”); Hampden’s Trial, 9 Cob. St. Tr. 1053, 1103 (K.B.1684) (With-ins, J.) (excluding evidence of prior forgeries from the trial of a man accused of forgery, explaining that the evidence would “rak[e] into men’s course of life, to pick up evidence that they cannot be prepared to answer to”). See generally Louis M. Natali, Jr. & R. Stephen Stigall, “Are You Going to Arraign His Whole Life?”: How Sexual Propensity Evidence Violates the Due Process Clause, 28 LOYOLA U. CHI. L.J. 1,12-23 (1996).
Accordingly, it may be true that the jury instruction in this case, which explicitly invited the jury to consider past crimes committed by Garceau as evidence of his guilt in this case, violated Garceau’s due process rights. Presuming, as we must, that the jury in this case followed its instructions, see, e.g., Weeks v. Angelone, 528 U.S. 225, 234, 120 S.Ct. 727, 145 L.Edüd 727 (2000), we must conclude that the jury considered Garceau’s prior crimes as evidence that he committed the crime for which he was being tried. Because such consideration puts a thumb on the prosecution’s side of the scales of justice and may well allow conviction on evidence that does not 'demonstrate guilt for this crime beyond a reasonable doubt, it seems fair to reason, as the majority does, that it violates the Due Process Clause. Cf. People v. Garceau, 6 Cal.4th 140, 24 Cal.Rptr.2d *783664, 862 P.2d 664, 691 (1993) (in bank) (noting that when “other crimes” evidence is considered to show propensity, it “invites the jury to be swayed by speculation that, because the defendant previously has murdered, he or she also committed the charged murder”).
II
Even assuming that Garceau suffered a violation of his constitutional rights, though, I simply cannot conclude that Gar-ceau is entitled to federal habeas relief. For even if the “prior crimes” instruction violated Garceau’s due process rights, on habeas review we may grant relief only if the alleged error “had substantial and injurious effect or influence in determining the jury’s verdict.” Brecht, 507 U.S. at 637, 113 S.Ct. 1710. That is, Garceau is entitled to habeas relief only if he can show that any constitutional violation “resulted in ‘actual prejudice.’ ” Id.
I begin by noting that, for purposes of this analysis, the introduction of evidence of Garceau’s prior crimes was not itself problematic. As the majority correctly points out, there was a permissible, non-propensity inference that the jury could have drawn from this evidence. See supra, Maj. Op. at 775 (admitting that in this case, “there is a permissible inference that the jury could draw from the other crimes evidence”). Indeed, as the California Supreme Court explained, the other-crimes evidence
was not introduced over the objection of the defense, but rather at its invitation. The defense sought to include such evidence in an effort to persuade the jury of the likelihood that some other member of the drug conspiracy killed Greg Rambo and the Bautistas.
Garceau, 24 Cal.Rptr.2d 664, 862 P.2d at 691. Thus, the only question to be answered is whether the giving of the “other crimes” instruction itself, which specifically invited the jury to draw the propensity inference, resulted in “actual prejudice” to Garceau under the highly deferential standard of Brecht. In my view, the answer to that question is emphatically “no.”
The majority analyzes the factors outlined in McKinney v. Rees, 993 F.2d 1378, 1384 (9th Cir.1993) and concludes that any constitutional error committed by the trial court when it gave the “other crimes” instruction was not harmless under Brecht. This analysis, though, ignores one unassailable truth about the facts of this case: the jury heard evidence that Garceau had killed Rambo only from the same drug partners who testified that he killed the Bautistas. The state did not introduce evidence of Garceau’s conviction for Rambo’s murder. As a result, the State’s entire case rested on the credibility of Garceau’s drug partners. Cf. Garceau, 24 Cal. Rptr.2d 664, 862 P.2d at 691 (explaining that “it was clear the defense desired that the jury consider th[e] [‘other crimes’] evidence for the purpose of establishing defendant’s innocence of the charged offenses”). That the jury convicted Garceau therefore strongly suggests that the jury found the State’s witnesses credible, and thus, only factors that eroded the credibility of the drug partners would have changed the outcome. I cannot believe that the jury would have believed Gar-eeau’s drug partners when they said that Garceau committed the other crimes, but then doubted them when they said that he committed the Bautista murders, only to have that doubt mollified by the propensity instruction. The jury either believed the testimony of the drug partners, or it did not. Because this credibility determination would not have been undermined by removing the propensity inference from the jury’s deliberations, I simply cannot comprehend how a proper jury instruction *784would have changed the outcome. Cf. Franklin v. Henry, 122 F.3d 1270, 1273(9th Cir.1997) (holding error not harmless where it undermined the credibility of key witnesses).
While the majority may be correct in asserting that the evidence of Garceau’s guilt was not, as the state contends, “overwhelming,” that is not to say that the propensity inference was the key to the State’s case on the question of Garceau’s guilt. Indeed, as I have already explained, the key to the state’s case was the credibility of Garceau’s drug partners — and the inference in no way affected that credibility. Accordingly, I am not persuaded that the instruction was harmful under Brecht Cf. Penry v. Johnson, 532 U.S. 782, 121 S.Ct. 1910, 1920, 150 L.Ed.2d 9 (2001) (concluding that any error in admitting evidence did not have a “substantial and injurious effect” on the verdict under Brecht where the evidence admitted “was by no means the key to the State’s case”).
Ill
No one seriously disputes that the jury instruction given in this case violated California evidentiary law. But that alone is not enough to merit federal habeas relief. As we have explained before,
We are not a state supreme court of errors; we do not review questions of state evidence law. On federal habeas we may only consider whether the petitioner’s conviction violated constitutional norms....
[Fjailure to comply with the state’s rules of evidence is neither a necessary nor a sufficient basis for granting habeas relief. While adherence to state evidentia-ry rules suggests that the trial was conducted in a procedurally fair manner, it is certainly possible to have a fair trial even when state standards are violated.... Jammal v. Van de Kamp, 926 F.2d 918, 919 (9th Cir.1991) (emphasis added). In this case, the propensity instruction may well have violated Garceau’s due process rights. But even that is not enough. As a federal habeas petitioner, Garceau must also show actual prejudice. This he has not done; thus, he is not entitled to habeas relief from this court. Because the majority today grants a new trial (or, alternatively, freedom) to a man who (i) was duly convicted under California law of brutally killing two innocent women, and (ii) is not being held in violation of the Constitution of the United States, I dissent.
. Of course, it is not clear that the majority could have reached this conclusion had it been forced to grapple with Teague v. Lane, 489 U.S. 288, 109 S.Ct. 1060, 103 L.Ed.2d 334 (1989) (plurality opinion). The Supreme Court has explained that in the usual federal habeas case, "[t]he application of Teague is a threshold question....” Goeke v. Branch, 514 U.S. 115, 117, 115 S.Ct. 1275, 131 L.Ed.2d 152 (1995) (per curiam). Teague, of course, bars a federal court considering a pre-AEDPA habeas petition from granting the petition where the vindicating a petitioner's claim would create a "new rule." Id. at 310, 109 S.Ct. 1060. Certainly, given that neither the Supreme Court nor this court has yet addressed the question that today's opinion answers, the state has at the very least a colorable argument that the majority today announces a "new rule,” on which it cannot grant Garceau relief. See O’Dell v. Netherland, 521 U.S. 151, 164, 117 S.Ct. 1969, 138 L.Ed.2d 351 (1997) (stating that a new tule is one that "a reasonable jurist ... would not have felt compelled to adopt”) (emphasis added).
Alas, the state did not raise Teague in its briefs before this court. And I recognize that we have discretion to consider Teague waived if it is not raised in the briefing. See, e.g., United States v. Navarro, 160 F.3d 1254, 1256 (9th Cir. 1998) (“Teague can be waived ....”) (citing Goeke, 514 U.S. at 116-18, 115 S.Ct. 1275). But given the majority's candid admission that the new rule it announces today is not compelled by any of our precedents, I would hesitate to forego a Teague analysis if the state had only implicitly waived Teague by failing to raise it in his briefs. See, e.g., Jackson v. Johnson, 217 F.3d 360, 361 (5th Cir.2000) ("[A]bsent compelling reasons to the contrary, a federal court should apply Teague even when it has been implicitly waived by the State.").
*782The state, though, went one step further. Asked at oral argument whether Teague applied to this case, counsel for the state lamely replied, “Teague has never been raised in this case.” When pressed from the bench, and given an opportunity to raise Teague, counsel impotently responded, "I don't know why Teague has never been raised in this case,” but did not, in fact, raise it. Because the state thus explicitly declined to invoke Teague, even when squarely presented with the opportunity to do so, I reluctantly conclude that it is inappropriate to analyze whether the Teague bar applies. I note with dismay, however, that the state has no one to blame but its own lawyer for the fact that the majority can apply its newly-minted rule in this case.