Justice Kennedy
delivered the opinion of the Court.
The death sentence of the petitioner in this case was decreed by a judgment that became final before we decided either Maynard v. Cartwright, 486 U. S. 356 (1988), or Clemons v. Mississippi, 494 U. S. 738 (1990). The petitioner argues that the State of Mississippi committed the same error in his case as it did in Clemons, and that under both Maynard and Clemons his sentence is unconstitutional. The question presented is whether in a federal habeas corpus proceeding a petitioner is foreclosed from relying on Maynard and Clemons because either or both announced a new rule as defined in Teague v. Lane, 489 U. S. 288 (1989).
I
In June 1982, Ray McWilliams and his wife, Nell, were shot to death in their Jackson, Mississippi, home as part of an armed robbery. The petitioner James R. Stringer did not fire the fatal shots, but he did plan the robbery and take part in it. The killing was part of his plan from the outset. The crimes, and their gruesome aspects, are described in the opinion of the Mississippi Supreme Court on direct review of the conviction and sentence. Stringer v. State, 454 So. 2d 468, 471-473 (1984).
Under Mississippi law the death sentence may be imposed for murders designated by statute as “capital murder.” Miss. Code Ann. § 97-3-19(2) (Supp. 1991). A killing in the course of a burglary or robbery is included within that category. Following a capital murder conviction, the jury in the Mississippi system proceeds to the sentencing phase of the case. For a defendant who has been convicted of capital murder to receive the death sentence, the jury must find at least one of eight statutory aggravating factors, and then it must determine that the aggravating factor or factors are not outweighed by the mitigating circumstances, if any. §99-19-101.
The jury found petitioner guilty of capital murder in the course of a robbery. In the sentencing phase the jury found that there were three statutory aggravating factors. The aggravating factors as defined in the jury instructions, and for the most part following the statutory wording, were:
“1. The Defendant contemplated that life would be taken and/or the capital murder was intentionally committed and that the Defendant was engaged in an attempt to commit a robbery; and was committed for pecuniary gain.
“2. The capital murder was committed for the purpose of avoiding or preventing the detection and lawful arrest of James R. Stringer, the Defendant.
“3. The capital murder was especially heinous, atrocious or cruel.” Brief for Respondents 4.
The trial court in its instructions did not further define the meaning of the third factor.
On direct review the Mississippi Supreme Court affirmed. Stringer v. State, supra. With respect to the sentence, the court found it was not “imposed under the influence of passion, prejudice or any other arbitrary factor,” id., at 478; “the evidence fully supported] the jury’s finding of statutorily required aggravating circumstances,” id., at 479; and the death sentence was not disproportionate to sentences imposed in other cases, ibid. Petitioner’s conviction became final when we denied certiorari on February 19,1985. Stringer v. Mississippi, 469 U. S. 1230. Postconviction relief was denied in the state courts. Stringer v. State, 485 So. 2d 274 (1986).
This case comes to us from proceedings begun when petitioner filed his first federal habeas petition in the United States District Court for the Southern District of Mississippi. The relevant claim is petitioner’s contention that the third aggravating factor found by the jury and considered in the sentencing proceeding, the “heinous, atrocious or cruel” aggravating factor, was so vague as to render the sentence arbitrary, in violation of the Eighth Amendment’s proscription of cruel and unusual punishment. The District Court found the claim subject to a procedural bar and, in the alternative, ruled it had no merit. Stringer v. Scroggy, 675 F. Supp. 356, 366 (1987).
Without consideration of the procedural bar question, the Court of Appeals affirmed on the merits, finding no constitutional infirmity in the jury’s consideration of the third aggravating factor because two other aggravating factors were unchallenged. Stringer v. Jackson, 862 F. 2d 1108 (CA5 1988). When the Court of Appeals affirmed, we had not decided Clemons v. Mississippi, and we later vacated its opinion for further consideration. 494 U. S. 1074 (1990). On remand the Court of Appeals held that petitioner was not entitled to rely on Clemons or the related case of Maynard v. Cartwright in his habeas corpus proceeding because those decisions announced a new rule after his sentence was final. 909 F. 2d 111 (1990). The court relied upon its earlier analysis in Smith v. Black, 904 F. 2d 950 (1990), cert. pending, No. 90-1164, a case that had also presented the question whether Clemons and Maynard announced a new rule. We granted certiorari, 500 U. S. 915 (1991), and now reverse.
I — l I — i
Subject to two exceptions, a case decided after a petitioner’s conviction and sentence became final may not be the predicate for federal habeas corpus relief unless the decision was dictated by precedent existing when the judgment in question became final. Butler v. McKellar, 494 U. S. 407 (1990); Penry v. Lynaugh, 492 U. S. 302 (1989); Teague v. Lane, 489 U. S. 288 (1989). As we explained in Butler, “[t]he ‘new rule’ principle ... validates reasonable, good-faith interpretations of existing precedents made by state courts even though they are shown to be contrary to later decisions.” 494 U. S., at 414. Neither one of the exceptions is at issue here, so our inquiry is confined to the question whether Clemons, Maynard, or both announced a new rule.
When a petitioner seeks federal habeas relief based upon a principle announced after a final judgment, Teague and our subsequent decisions interpreting it require a federal court to answer an initial question, and in some cases a second. First, it must be determined whether the decision relied upon announced a new rule. If the answer is yes and neither exception applies, the decision is not available to the petitioner. If, however, the decision did not announce a new rule, it is necessary to inquire whether granting the relief sought would create a new rule because the prior decision is applied in a novel setting, thereby extending the precedent. See Butler v. McKellar, supra, at 414-415. The interests in finality, predictability, and comity underlying our new rule jurisprudence may be undermined to an equal degree by the invocation of a rule that was not dictated by precedent as by the application of an old rule in a manner that was not dictated by precedent.
A
A determination whether Maynard and Clemons announced a new rule must begin with Godfrey v. Georgia, 446 U. S. 420 (1980). In Godfrey we invalidated a death sentence based upon the aggravating circumstance that the killing was “outrageously or wantonly vile, horrible and inhuman.” Id., at 428-429. The formulation was deemed vague and imprecise, inviting arbitrary and capricious application of the death penalty in violation of the Eighth Amendment. We later applied the same analysis and reasoning in Maynard. In Maynard the aggravating circumstance under an Oklahoma statute applied to a killing that was “especially heinous, atrocious, or cruel.” 486 U. S., at 359. We found the language gave no more guidance than did the statute in Godfrey, and we invalidated the Oklahoma formulation. 486 U. S., at 363-364.
In the case now before us Mississippi does not argue that Maynard itself announced a new rule. To us this appears a wise concession. Godfrey and Maynard did indeed involve somewhat different language. But it would be a mistake to conclude that the vagueness ruling of Godfrey was limited to the precise language before us in that case. In applying Godfrey to the language before us in Maynard, we did not “brea[k] new ground.” Butler v. McKellar, supra, at 412. Maynard was, therefore, for purposes of Teague, controlled by Godfrey, and it did not announce a new rule.
B
Of more substance is the State’s contention that it was a new rule to apply the Godfrey and Maynard holdings to the Mississippi sentencing process. The State argues this must have been an open question when petitioner’s sentence became final, with Clemons yet undecided. We acknowledge there are differences in the use of aggravating factors under the Mississippi capital sentencing system and their use in the Georgia system in Godfrey. In our view, however, those differences could not have been considered a basis for denying relief in light of precedent existing at the time petitioner’s sentence became final. Indeed, to the extent that the differences are significant, they suggest that application of the Godfrey principle to the Mississippi sentencing process follows, a fortiori, from its application to the Georgia system.
1
The principal difference between the sentencing schemes in Georgia and Mississippi is that Mississippi is what we have termed a “weighing” State, while Georgia is not. See Clemons v. Mississippi, 494 U. S., at 745; Parker v. Dugger, 498 U. S. 308, 318 (1991). Under Mississippi law, after a jury has found a defendant guilty of capital murder and found the existence of at least one statutory aggravating factor, it must weigh the aggravating factor or factors against the mitigating evidence. By contrast, in Georgia the jury must find the existence of one aggravating factor before imposing the death penalty, but aggravating factors as such have no specific function in the jury’s decision whether a defendant who has been found to be eligible for the death penalty should receive it under all the circumstances of the case. Instead, under the Georgia scheme, “ ‘[i]n making the decision as to the penalty, the factfinder takes into consideration all circumstances before it from both the guilt-innocence and the sentence phases of the trial. These circumstances relate both to the offense and the defendant.’” Zant v. Stephens, 462 U. S. 862, 872 (1983) (quoting the response of the Georgia Supreme Court to our certified question).
That Mississippi is a weighing State only gives emphasis to the requirement that aggravating factors be defined with some degree of precision. By express language in Zant we left open the possibility that in a weighing State infection of the process with an invalid aggravating factor might require invalidation of the death sentence. Id., at 890. Although we later held in Clemons v. Mississippi that under such circumstances a state appellate court could reweigh the aggravating and mitigating circumstances or undertake harmless-error analysis, we have not suggested that the Eighth Amendment permits the state appellate court in a weighing State to affirm a death sentence without a thorough analysis of the role an invalid aggravating factor played in the sentencing process.
We require close appellate scrutiny of the import and effect of invalid aggravating factors to implement the well-established Eighth Amendment requirement of individualized sentencing determinations in death penalty cases. See Zant, supra, at 879; Eddings v. Oklahoma, 455 U. S. 104, 110-112 (1982); Lockett v. Ohio, 438 U. S. 586, 601-605 (1978) (plurality opinion); Roberts v. Louisiana, 431 U. S. 633, 636-637 (1977); Gregg v. Georgia, 428 U. S. 153, 197 (1976) (joint opinion of Stewart, Powell, and Stevens, JJ.); Woodson v. North Carolina, 428 U. S. 280, 303-304 (1976) (plurality opinion). In order for a state appellate court to affirm a death sentence after the sentencer was instructed to consider an invalid factor, the court must determine what the sentencer would have done absent the factor. Otherwise, the defendant is deprived of the precision that individualized consideration demands under the Godfrey and Maynard line of cases.
These principles of appellate review were illustrated by our decision in Barclay v. Florida, 463 U. S. 939 (1983). Florida, like Mississippi, is a weighing State, Parker v. Dugger, supra, at 318, and the trial judge imposes the sentence based upon a recommendation from the jury. In Barclay the sentencing judge relied on an aggravating factor that was not a legitimate one under state law. We affirmed the sentence, but only because it was clear that the Florida Supreme Court had determined that the sentence would have been the same had the sentencing judge given no weight to the invalid factor. See 463 U. S., at 958 (plurality opinion); id., at 973-974 (Stevens, J., concurring in judgment). Therefore, contrary to the dissent’s suggestion, post, at 245-247, the fact that both principal opinions in Barclay focused on the weight the sentencer gave to an invalid aggravating factor demonstrates that a reviewing court in a weighing State may not make the automatic assumption that such a factor has not infected the weighing process. In short, it may not make the automatic assumption that Stringer claims the Mississippi Supreme Court made in this case.
In view of the well-established general requirement of individualized sentencing and the more specific requirement that a sentence based on an improper factor be reassessed with care to assure that proper consideration was given, there was no arguable basis to support the view of the Court of Appeals that at the time petitioner’s sentence became final the Mississippi Supreme Court was permitted to apply a rule of automatic affirmance to any death sentence supported by multiple aggravating factors, when one is invalid.
With respect to the function of a state reviewing court in determining whether the sentence can be upheld despite the use of an improper aggravating factor, the difference between a weighing State and a nonweighing State is not one of “semantics,” as the Court of Appeals thought, Stringer v. Jackson, 862 F. 2d, at 1115, but of critical importance. In a nonweighing State, so long as the sentencing body finds at least one valid aggravating factor, the fact that it also finds an invalid aggravating factor does not infect the formal process of deciding whether death is an appropriate penalty. Assuming a determination by the state appellate court that the invalid factor would not have made a difference to the jury’s determination, there is no constitutional violation resulting from the introduction of the invalid factor in an earlier stage of the proceedings. But when the sentencing body is told to weigh an invalid factor in its decision, a reviewing court may not assume it would have made no difference if the thumb had been removed from death’s side of the scale. When the weighing process itself has been skewed, only constitutional harmless-error analysis or reweighing at the trial or appellate level suffices to guarantee that the defendant received an individualized sentence. This clear principle emerges not from any single case, as the dissent would require, post, at 243-247, but from our long line of authority setting forth the dual constitutional criteria of precise and individualized sentencing. Thus, the principal difference between the sentencing systems of Mississippi and Georgia, the different role played by aggravating factors in the two States, underscores the applicability of Godfrey and Maynard to the Mississippi system.
2
Although it made no similar argument in Clemons itself, the State contends now that before Clemons it was reasonable to believe there was no constitutional requirement to define aggravating factors with precision in the Mississippi system. It points to the fact that in order for a jury to find a defendant guilty of capital murder it must find that the crime fits within the narrow and precise statutory definition of that offense. Any additional consideration of aggravating factors during the sentencing phase, under this view, is of no constitutional significance because the requisite differentiation among defendants for death penalty purposes has taken place during the jury’s deliberation with respect to guilt. The State cites our decision in Lowenfield v. Phelps, 484 U. S. 231 (1988), in support of its analysis. But Lowenfield, arising under Louisiana law, is not applicable here and does not indicate that Clemons imposed a new rule.
In Louisiana, a person is not eligible for the death penalty unless found guilty of first-degree homicide, a category more narrow than the general category of homicide. 484 U. S., at 241. A defendant is guilty of first-degree homicide if the Louisiana jury finds that the killing fits one of five statutory criteria. See id., at 242 (quoting La. Rev. Stat. Ann. § 14:30A (West 1986)). After determining that a defendant is guilty of first-degree murder, a Louisiana jury next must decide whether there is at least one statutory aggravating circumstance and, after considering any mitigating circumstances, determine whether the death penalty is appropriate. 484 U. S., at 242. Unlike the Mississippi process, in Louisiana the jury is not required to weigh aggravating against mitigating factors.
In Lowenfield, the petitioner argued that his death sentence was invalid because the aggravating factor found by the jury duplicated the elements it already had found in determining there was a first-degree homicide. We rejected the argument that, as a consequence, the Louisiana sentencing procedures had failed to narrow the class of death-eligible defendants in a predictable manner. We observed that “[t]he use of ‘aggravating circumstances’ is not an end in itself, but a means of genuinely narrowing the class of death-eligible persons and thereby channeling the jury’s discretion. We see no reason why this narrowing function may not be performed by jury findings at either the sentencing phase of the trial or the guilt phase.” Id., at 244-246. We went on to compare the Louisiana scheme with the Texas scheme, under which the required narrowing occurs at the guilt phase. Id., at 246 (discussing Jurek v. Texas, 428 U. S. 262 (1976)). We also contrasted the Louisiana scheme with the Georgia and Florida schemes. 484 U. S., at 246.
The State’s premise that the Mississippi sentencing scheme is comparable to Louisiana’s is in error. The Mississippi Supreme Court itself has stated in no uncertain terms that, with the exception of one distinction not relevant here, its sentencing system operates in the same manner as the Florida system; and Florida, of course, is subject to the rule forbidding automatic affirmance by the state appellate court if an invalid aggravating factor is relied upon. In considering a Godfrey claim based on the same factor at issue here, the Mississippi Supreme Court considered decisions of the Florida Supreme Court to be the most appropriate source of guidance. In Gilliard v. State, 428 So. 2d 576, 586 (1983), the Mississippi Supreme Court compared the claim before it to the claim in Dobbert v. State, 375 So. 2d 1069 (Fla. 1979), cert. denied, 447 U. S. 912 (1980). The court stated:
“In Dobbert. . . the Florida Supreme Court held that even though the lower court considered two circumstances which would not pass constitutional muster and did not amount to aggravating circumstances, there was one aggravating circumstance which existed and that it was sufficient to uphold the death penalty. The only distinction between Dobbert and the present case is that in Dobbert, under Florida law, the judge determined the sentence without a jury.” Gilliard, supra, at 586.
Whether the Mississippi Supreme Court in Gilliard was adopting the kind of harmless-error rule we approved in Barclay, 463 U. S., at 958, and if so, whether it applied that same rule in Stringer’s case, are questions relating to the merits of Stringer’s claim which we need not consider here. What is dispositive is the fact that the Mississippi Supreme Court, which is the final authority on the meaning of Mississippi law, has at all times viewed the State’s sentencing scheme as one in which aggravating factors are critical in the jury’s determination whether to impose the death penalty. See also Evans v. State, 422 So. 2d 737, 743 (Miss. 1982) (applying Godfrey). It would be a strange rule of federalism that ignores the view of the highest court of a State as to the meaning of its own law. See Teague v. Lane, 489 U. S., at 310 (discussing federalism as one of the concerns underlying the nonretroactivity principle).
As a matter of federal law, moreover, the view of the Mississippi Supreme Court that Godfrey’s dictates apply to its capital sentencing procedure is correct. Indeed, it is so evident that the issue was not even mentioned in Clemons. There we took for granted, and the State did not challenge, the proposition that if a State uses aggravating factors in deciding who shall be eligible for the death penalty or who shall receive the death penalty, it cannot use factors which as a practical matter fail to guide the sentencer’s discretion. See Clemons, 494 U. S., at 756, n. 1 (opinion of Blackmun, J., joined by Brennan, Marshall, and Stevens, JJ., concurring in part and dissenting in part) (noting that the unconstitutionality of the vague aggravating factor is implicit in the Court’s opinion).
Even were we free to ignore the Mississippi Supreme Court’s understanding of the way its own law works, we would reject the suggestion that Lowenfield could form the basis for an argument that Godfrey does not apply to Mississippi. Although our precedents do not require the use of aggravating factors, they have not permitted a State in which aggravating factors are decisive to use factors of vague or imprecise content. A vague aggravating factor employed for the purpose of determining whether a defendant is eligible for the death penalty fails to channel the sen-tencer’s discretion. A vague aggravating factor used in the weighing process is in a sense worse, for it creates the risk that the jury will treat the defendant as more deserving of the death penalty than he might otherwise be by relying upon the existence of an illusory circumstance. Because the use of a vague aggravating factor in the weighing process creates the possibility not only of randomness but also of bias in favor of the death penalty, we cautioned in Zant that there might be a requirement that when the weighing process has been infected with a vague factor the death sentence must be invalidated.
Nothing in Lowenfield suggests that the proscription of vague aggravating factors does not apply to a capital sentencing system like Mississippi’s. Lowenfield did not involve a claim that a statutory aggravating factor was ambiguous, and its relevance to Godfrey, which it did not find it necessary to cite, or the line of cases following from Godfrey, is slight at best.
We also note that the State’s reliance on Lowenfield to show that it could not have anticipated Godfrey’s application to Mississippi is somewhat odd. For Lowenfield, after all, was decided when the petitioner’s conviction and sentence already were final. It is a fiction for the State to contend that in 1984 its courts relied on a 1988 decision. This is not to say that a State could not rely on a decision announced after a petitioner’s conviction and sentence became final to defeat his claim on the merits. It could. Insofar as our new rule jurisprudence “validates reasonable, good-faith interpretations of existing precedents,” Butler v. McKellar, 494 U. S., at 414, however, the State may have little cause to complain if in deciding to allow a petitioner to rely upon a decision the federal courts look only to those precedents which the state courts knew at the relevant time. In any event, we need not dwell on the anachronism inherent in the State’s Lowenfield argument because, as we have concluded, that case does not provide a basis for concluding that it was a new rule to apply Godfrey to the Mississippi system.
The State next argues that Clemons’ application of God-frey to Mississippi could not have been dictated by precedent because prior to Clemo'ns the Fifth Circuit concluded that Godfrey did not apply to Mississippi. See Evans v. Thigpen, 809 F. 2d 239, cert. denied, 483 U. S. 1033 (1987); Johnson v. Thigpen, 806 F. 2d 1243 (1986), cert. denied, 480 U. S. 951 (1987). Before addressing the merits of this argument we reiterate that the rationale of the Fifth Circuit has not been adopted by the Mississippi Supreme Court, which, ás a state court, is the primary beneficiary of the Teague doctrine. The Mississippi Supreme Court has recognized that it is bound by Godfrey. See, e. g., Mhoon v. State, 464 So. 2d 77, 85 (1985) (requiring, based on Godfrey, that a capital sentencing jury be given a narrowing construction of the “heinous, atrocious or cruel” factor).
The Fifth Circuit’s pre-Clemons views are relevant to our inquiry, see Butler, supra, at 415, but not dispositive. The purpose of the new rule doctrine is to validate reasonable interpretations of existing precedents. Reasonableness, in this as in many other contexts, is an objective standard, and the ultimate decision whether Clemons was dictated by precedent is based on an objective reading of the relevant cases. The short answer to the State’s argument is that the Fifth Circuit made a serious mistake in Evans v. Thigpen and Johnson v. Thigpen. The Fifth Circuit ignored the Mississippi Supreme Court’s own characterization of its law and accorded no significance to the fact that in Mississippi aggravating factors are central in the weighing phase of a capital sentencing proceeding. As we have explained, when these facts are accorded their proper significance, the precedents even before Maynard and Clemons yield a well-settled principle: Use of a vague or imprecise aggravating factor in the weighing process invalidates the sentence and at the very least requires constitutional harmless-error analysis or reweighing in the state judicial system.
We reverse the decision of the Court of Appeals and remand the case for further proceedings consistent with this opinion.
It is so ordered.
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