OPINION
RYAN, Circuit Judge.
Gary Bradford Cone was sentenced to death in a Tennessee state court for a double murder of an elderly couple and his conviction and death sentence were affirmed by the Tennessee Supreme Court.
On this appeal from the district court’s denial of Cone’s petition for habeas corpus relief, we are asked to decide
• Whether Cone was sentenced to death in violation of the prohibition against cruel or unusual punishment of the Eighth Amendment of the United States Constitution.
Before we may reach that question, however, we must resolve two rather complex and interrelated questions of state procedural law.
• The first, is whether, under Tennessee law, the state supreme court implicitly reviews death penalty sentences for arbitrariness, even in cases in which the issue is not raised explicitly.
• The second, is whether the petitioner procedurally defaulted, in the state court, the Eighth Amendment issue he asks us to decide.
Our answer to the first state law question is yes, and to the second, it is no. Given our resolution of these issues, we are authorized to reach the Eighth Amendment issue, for which the petitioner has brought this appeal. As to that issue, we hold that petitioner Cone’s death sentence must be vacated because one of the statutory aggravating circumstances the jury relied upon in imposing the death sentence — that the murders were “especially heinous, atrocious, or cruel” — is unconstitutionally vague, and therefore, violates the Eighth Amendment.
I.
Cone was sentenced to death in a Tennessee court in 1982 following his conviction for the brutal murders of an elderly couple, Shipley and Cleopatra Todd. The facts of the case are fully detailed in our previous decision in Cone v. Bell, 243 F.3d 961 (6th Cir.2001), rev’d, 535 U.S. 685, 122 S.Ct. 1843, 152 L.Ed.2d 914 (2002), and need not be recounted here. It is necessary, however, to detail the procedural history of the case in order to explain why we have the case on appeal for a second time [788]*788and to explain the basis for the State’s argument that Cone has procedurally defaulted the Eighth Amendment issue he now asks us to decide.
Cone challenged his conviction and sentence on direct review in the Tennessee Supreme Court, which conducted a mandatory death penalty review pursuant to Tenn.Code Ann. § 39-2-205 (1982) (current version at TenmCode Ann. § 39-13-206 (2003)). State v. Cone, 665 S.W.2d 87 (Tenn.1984). The Tennessee court affirmed Cone’s murder convictions, and then, as it was required to do, considered the validity of the aggravating circumstances relied on by the jury in imposing the death penalty. Id. at 94^96. Under Tennessee law as it existed at the time-of Cone’s conviction, a jury could impose the death penalty only if it found that the prosecution had proved, beyond a reasonable doubt, the existence of at least one of twelve aggravating factors. Tenn.Code Ann. § 39-2404(i) (1981) (current version at TenmCode Ann. § 39-13-204(0 (2003)). In Cone’s case the jury found four aggravating factors, which were defined in the statute as follows:
(2) The defendant was previously convicted of one or more felonies, other than the present charge, which involve the use or threat of violence to the person.
(3) The defendant knowingly created a great risk of death to two or more persons, other than the victim murdered, during his act of murder.
(5) The murder was especially heinous, atrocious, or cruel in that it involved torture or depravity of mind.
(6) The murder was committed for the purpose of avoiding, interfering with, or preventing a lawful arrest or prosecution of the defendant or another.
TenmCode Ann. § 39-2404(i) (1981). In its review of the jury’s findings, the Tennessee Supreme Court first noted that the jury had failed to find one aggravating factor, that the crime was committed in the course of committing another felony (felony-murder), even though the evidence clearly would have supported it. State v. Cone, 665 S.W.2d at 94.
The court then reviewed the four aggra-vators the jury did find, and concluded (1) that the evidence supported the finding that Cone had been convicted previously of one or more felonies involving violence, id.; (2) that the evidence supported the finding that the murders were “especially heinous, atrocious, or cruel in that they involved torture or depravity of mind,” id. at 94-95; (3) that the evidence supported the finding that the murders were committed for the purpose of preventing a lawful arrest or prosecution, id. at 95; and (4) that the evidence was insufficient to support the jury’s affirmative finding that the petitioner “ ‘knowingly created a great risk of death to two (2) or more persons, other than the victim murdered, during [the] act of murder,’ ” id. (citation omitted). But the court found this error to be “harmless beyond a reasonable doubt” in light of the three other aggravating circumstances found by the jury and the court’s conclusion that the jurors should have found, although they did not, the additional ag-gravator, that the petitioner was guilty of felony-murder. Id. Accordingly, the court affirmed Cone’s death sentence. The constitutionality of the jury’s finding that the murders were “especially heinous, atrocious, or cruel,” which we hereafter refer to as the “HAC” aggravator, is a fundamental issue in this case.
Cone filed his first state post-conviction petition in the state trial court on June 22, 1984, attacking his conviction and death sentence. He alleged numerous violations [789]*789of his rights under the United States Constitution including prosecutorial misconduct and the ineffective assistance of counsel at trial. The trial court held a hearing and denied Cone’s petition. The Tennessee Court of Criminal Appeals affirmed the denial and the Tennessee Supreme Court declined Cone’s request to appeal.
Approximately five years later, in June 1989, Cone filed a second state post-conviction petition, followed by several amendments. In this second petition, Cone alleged numerous constitutional violations including, for the first time, an Eighth Amendment claim that the language of the HAC aggravator considered by the jury in the sentencing phase was unconstitutionally vague. The trial court dismissed the second petition as barred by the successive petition restrictions of Tennessee’s post-conviction statute, Tenn.Code Ann. § 40-30-111 (1990) (since repealed), holding that all the grounds raised in the second petition were barred because they either had been previously determined or were waived. This judgment was affirmed by the Tennessee Court of Criminal Appeals, and the Tennessee Supreme Court denied an application for permission to appeal. The United States Supreme Court denied Cone’s petition for a writ of certiorari.
Cone then filed a motion in federal district court to stay his execution. The district court granted the stay and Cone filed a petition for a writ of habeas corpus under 28 U.S.C. § 2254. The district court denied the § 2254 petition and lifted the stay of execution. We then granted Cone’s motion for a certificate of appeala-bility.
After briefing and oral argument, we granted Cone’s habeas petition with respect to his death sentence because we thought he had been unconstitutionally denied the effective assistance of counsel at sentencing. We found it unnecessary to decide several of Cone’s other sentencing claims, including his “Eighth Amendment cruel and unusual punishment argument and his argument concerning the application of aggravating circumstances.” Cone, 243 F.3d at 975. In Bell v. Cone, 535 U.S. 685, 122 S.Ct. 1843, 152 L.Ed.2d 914 (2002), the U.S. Supreme Court reversed our decision on the ineffective assistance of counsel issue and remanded to this court for further proceedings, which we understand to mean consideration of the sentencing issues that Cone raised and we did not reach in our previous decision.
II.
“An appellate court reviews a district court’s decision to deny or grant a writ of habeas corpus de novo, but it reviews the district court’s factual findings only for clear error.” Barker v. Yukins, 199 F.3d 867, 870 (6th Cir.1999).
III.
Initially, we must take up the State’s argument that Cone’s Eighth Amendment claim that the HAC aggravating factor was unconstitutionally vague, first raised in his second petition for post-conviction relief, had been procedurally defaulted. We address this issue first because, as a general rule, on habeas review, federal courts may not consider procedurally defaulted claims. Seymour v. Walker, 224 F.3d 542, 549-50 (6th Cir.2000). A claim is procedurally defaulted if: (1) the petitioner failed to comply with an applicable state procedural rule; (2) the state courts actually enforced the procedural rule; and (3) the state courts’ finding of noncompliance is an adequate and independent state ground for denying relief on the federal constitutional claim. Maupin v. Smith, 785 F.2d 135, 138 (6th Cir.1986).
[790]*790Under Tennessee law at the time of Cone’s conviction, grounds for relief that had been previously determined or waived were not cognizable in a state post-conviction action. Tenn.Code Ann. § 40-30-111 (since repealed). In its consideration on appeal of the denial of Cone’s second post-conviction petition, the Tennessee Court of Criminal Appeals refused to address Cone’s constitutional challenge to the HAC aggravator because, according to the court, it had been either previously determined or waived. Cone v. State, 927 S.W.2d 579, 582 (Tenn.Crim.App.1995). Of these two possibilities, “previously determined” or “waived,” we must determine which one actually describes the status of Cone’s constitutional claim in the state courts. If Cone waived his claim, then such waiver will constitute a procedural default and will serve as an adequate and independent state ground barring habeas review in this court. If Cone’s claim was previously determined, then we must decide whether the state courts’ determination “resulted in a decision that was contrary to, or involved an unreasonable application of, clearly established Federal law, as determined by the Supreme Court of the United States.” 28 U.S.C. § 2254(d)(1) (West Supp.2003).
Cone argues that he did not procedurally default on his Eighth Amendment vagueness challenge to the HAC aggravating factor, because the Tennessee Supreme Court “necessarily reviewed” the claim as part of its mandatory death penalty review.
In death penalty cases the Tennessee Supreme Court is required to conduct a mandatory death penalty review to determine whether:
(1) The sentence of death was imposed in any arbitrary fashion;
(2) The evidence supports the jury’s findings of a statutory aggravating circumstance or statutory aggravating circumstances;
(3) The evidence supports the jury’s finding of the absence of any mitigating circumstances sufficiently substantial to outweigh the aggravating circumstance or circumstances so found; and
(4) The sentence of death is excessive or disproportionate to the penalty imposed in similar cases, considering both the nature of the crime and the defendant.
Tenn.Code Ann. § 39-2-205(c) (1982) (emphasis added) (current version at Tenn. Code. Ann. § 39-13-206(c)(l) (2003)).
Tennessee responds that Cone’s “necessarily reviewed” claim, also known as “implicit review,” proves too much, since it would eviscerate the procedural default doctrine with respect to all constitutional claims.
The U.S. Courts of Appeals are divided on whether these state mandatory review statutes create an implicit review of constitutional challenges not explicitly raised. The Fourth, Eighth, and Eleventh Circuits all have rejected the implicit review argument. See Mu’min v. Pruett, 125 F.3d 192, 197 (4th Cir.1997); Nave v. Delo, 62 F.3d 1024, 1039 (8th Cir.1995); Julius v. Johnson, 840 F.2d 1533, 1546 (11th Cir.1988). The Ninth Circuit reached the opposite conclusion in an Idaho death penalty case, albeit in dicta. See Beam v. Paskett, 3 F.3d 1301, 1306 (9th Cir.1993), overruled on other grounds by Lambright v. Stewart, 191 F.3d 1181 (9th Cir.1999).
This court, in Coe v. Bell, 161 F.3d 320 (6th Cir.1998), in dicta, expressed discomfort with the implicit review argument in the context of a challenge to jury instructions on unanimity in sentencing in a death penalty case in a Tennessee court. Id. at 336. We stated that the argument that “the [Tennessee] supreme court has to review significant errors, whether or not [791]*791they were raised by the defendant,” is “too broad, as it would eliminate the entire doctrine of procedural bar in Tennessee in capital cases.” Id. Despite these reservations, we recognized in Coe that Tennessee courts had been moderately receptive to the implicit review theory. Id. For example, in State v. Martin, 702 S.W.2d 560 (Tenn.1985), overruled on other grounds by State v. Brown, 836 S.W.2d 530 (1992), the Tennessee Supreme Court stated that it was “required by statute to review the sentence and to consider significant errors whether or not called to the attention of the trial coiwt” Id. at 564 (emphasis added). We explained in Coe that, based on Martin, a procedural default could not arise under Tennessee law when a capital defendant raised an issue on appeal which he had failed to preserve properly during trial. Coe, 161 F.3d at 336. Thus, in Coe, we partially adopted the implicit review theory, but only to the extent of issues that were explicitly raised on appeal, even though not properly preserved in the trial court. Of course, unlike Coe, Cone’s unconstitutional HAC aggravator issue was not explicitly raised either in the trial court or on direct review in the Tennessee Supreme Court.
The eases that divide the circuits on the implicit review theory agree on one point: “The scope of the state court’s mandatory review is, ultimately, a question of state law.” Nave, 62 F.3d at 1039. Accordingly, if Tennessee construes its mandatory review statute to encompass constitutional issues not explicitly raised on direct review, then the Tennessee Supreme Court must be deemed to have considered the constitutionality of the HAC aggravator in this case, and Cone did not procedurally default on the claim.
It is important to frame this preliminary question of state law carefully. We understand the question to be whether it is the law in Tennessee that in all capital punishment cases, the Tennessee Supreme Court reviews the sentencing proceedings to ensure that the jurors have not imposed the death penalty “in any arbitrary fashion,” Tenn.Code Ann. § 39-2-205(c) (1982), even in cases in which the issue is not raised on direct review.
Just three years ago, in State v. West, 19 S.W.3d 753 (Tenn.2000), the Tennessee Supreme Court considered whether a defendant could raise an issue in his state post-conviction petition that he had not raised on direct review. Id. at 754. The court prefaced its discussion as follows:
In this appeal of a post-conviction proceeding, ... the appellant[ ] raises for the first time the issue whether evidence adduced at the sentencing phase of his trial was sufficient to support the jury’s conclusion that he committed two murders for the purpose of avoiding arrest or prosecution. Although [the appellant] casts the issue as concerning the evidentiary sufficiency of the (i)(6) aggravating circumstance, we think his grievance involves instead the constitutional issue of whether the aggravating circumstance narrows the class of death eligible offenders. He says that it does not, and because it does not, he contends that it violates the Eighth Amendment.
Id. (emphasis added). The court’s reference to “narrow[ing] the class of death eligible offenders” is responsive to the rule announced in Zant v. Stephens, 462 U.S. 862, 103 S.Ct. 2733, 77 L.Ed.2d 235 (1983), that in capital punishment cases, the “aggravating circumstance must genuinely narrow the class of persons eligible for the death penalty” in order to ensure that the jury’s discretion in imposing the death sentence is “adequately ... channelled].” Id. at 877. Later Supreme Court cases have characterized death sentences imposed without appropriately narrowing instruc[792]*792tions as having been imposed arbitrarily and upon criteria, i.e., statutory aggravating factors, whose language is unconstitutionally vague. See, e.g., Tuilaepa v. California, 512 U.S. 967, 974-75, 114 S.Ct. 2630, 129 L.Ed.2d 750 (1994); Sawyer v. Whitley, 505 U.S. 333, 367, 112 S.Ct. 2514, 120 L.Ed.2d 269 (1992) (Stevens, J., concurring).
The emphasized language in West is significant because the court characterized the issue as an Eighth Amendment vagueness challenge to a statutory aggravating factor, the precise issue raised by Cone. In West, the State argued that the defendant could not raise the vagueness issue in his post-conviction petition for two reasons: (1) he had failed to raise it on direct appeal and thus “waived” it; and, alternatively, (2) it had been “previously determined” due to the Tennessee Supreme Court’s mandatory review. West, 19 S.W.3d at 756. The court agreed with the State, but, in a seeming contradiction, held that the vagueness issue had been both “previously determined” and “waived” as a result of West’s direct appeal. Id. Specifically, the court stated:
Under Tenn.Code Ann. § 40 — 30—112(b), when [the appellant] failed to raise the (i)(6) issue on direct appeal, he effectively blocked any consideration of this issue by this Court on post-conviction review. Additionally, under Tenn.Code Ann. § 39-2~205(c)(3) (1982) (repealed 1989), this Court was required in all cases in which the death penalty was imposed to automatically consider whether the “evidence supports the jury’s finding of a statutory aggravating circumstance or statutory aggravating circumstances .... ” Pursuant to these mandatory provisions, this Court found that the .requirements of the statute had, in fact, been met in [the appellant’s] case. Thus, we conclude that the issue under discussion has, indeed, been both “previously determined” and “waived,” under the definitions provided in Tenn.Code Ann. § 40-30-112(a) and (b).
Id. (emphasis added) (internal citations omitted).
Although West appears to stand alone as direct support for the implicit review argument, other Tennessee Supreme Court cases lend moderate support. In Martin, discussed above, the court held that it was “required by statute to review the sentence and to consider significant errors whether or not called to the attention of the trial court.” 702 S.W.2d at 564 (emphasis added). Likewise, in State v. Duncan, 698 S.W.2d 63 (Tenn.1985), the court stated: “in cases where the defendant is under sentence of death, this court is under the duty to ‘automatically’ review the sentence, which imposes the burden on this court to consider any alleged error, whether called to the trial court’s attention or not.” Id. at 67-68 (emphasis added). Finally, in State v. Nesbit, 978 S.W.2d 872 (Tenn.1998), the court held that the mandatory review statute gave it jurisdiction to review issues raised by the defendant’s appeal despite the defendant’s failure to timely file his appeal. Id. at 880-81. These three cases make clear that the Tennessee Supreme Court considers its task when conducting the required review to be important enough to warrant departures from procedural rules that would normally bar supreme court review. In each of these three cases, however, unlike this case, the issue was raised by the defendant on direct review.
The conceptual leap from claims explicitly raised on direct appeal, although not properly preserved, to claims not raised at all is significant and, without West, there would be no Tennessee authority for attempting it. Nevertheless, West cannot be ignored; neither can the Ten[793]*793nessee statute, which mandates supreme court review to assure that no death sentence is “imposed in any arbitrary fashion.” TenmCode Ann. § 39-2-205(e)(l) (1982). It is also significant that the statute does not condition the mandatory review upon the issues named in the statute being properly raised. The following factors in West strongly favor the conclusion that it is the law in Tennessee that the supreme court “implicitly” reviews death sentences for ai'bitrariness, even if the issue is not explicitly raised on direct appeal: (1) the language that in “all” death penalty cases, the court “automatically” complies with the mandatory review statute; (2) the court’s re-characterization of the appellant’s “evidentiary sufficiency” challenge as a vagueness (ie., arbitrariness) challenge; and (3) its holding that the same was “previously determined” (although never raised by the appellant). We can find no other logical construction to put upon the court’s language in West
We note, in passing, that the implicit review doctrine, as we apply it today in this case, does not foreclose the possibility that other death penalty defendants may procedurally default on other constitutional issues not raised on direct appeal. The language of Tennessee’s mandatory review statute provides a basis to distinguish between vagueness challenges and other constitutional claims, since it requires the Tennessee Supreme Court to look specifically for sentences “imposed in any arbitrary fashion.” The “evil” of vague sentencing instructions is, precisely, that they invite arbitrary decision-making. As the U.S. Supreme Court has stated: “orn-eases have insisted that the channeling and limiting of the sentencer’s discretion in imposing the death penalty is a fundamental constitutional requirement for sufficiently minimizing the risk of wholly arbitrary and capricious action.” Maynard v. Cartwright, 486 U.S. 356, 362, 108 S.Ct. 1853, 100 L.Ed.2d 372 (1988). Because there are other constitutional violations that do not pose this same risk, the implicit review principle we have applied today would not necessarily save those claims from procedural default.
We think that given the holding in West, and the court’s language explaining it, we must conclude that the Tennessee Supreme Court implicitly considered and rejected Cone’s unmentioned vagueness “challenge” to the HAC aggravator, in the course of its mandatory review. As such, Cone’s claim must be deemed to have been decided on the merits during the direct appeal and, therefore, when the Tennessee lower courts disposed of the claim on procedural grounds they did so not because the claim was “waived” but because it was “previously determined.”
This conclusion would seem to be confirmed by the written findings of the state trial court dismissing Cone’s second amended petition for post-conviction review. Referring to the specific paragraph of the petition in which Cone raised his vagueness challenge for the first time, the trial court stated: “grounds ... [appearing in paragraph] 18 ... involve[ ] a potpourri of various errors by the court at the trial all of which grounds have been considered and denied in direct appeal or the First Post Conviction Petition.” Cone v. State, No. P-06874, slip op. at 4 (Crim. Ct. Tenn., 13th Judicial Dist., Dec. 16, 1993) (emphasis added). The Tennessee Court of Criminal Appeals, the last state court to render an opinion on Cone’s petition, affirmed the holding of the trial court and, in fact, commended the trial court judge for his “exemplary and meticulous treatment of the appellant’s petition.” Cone v. State, 927 S.W.2d at 581. These statements by the lower state courts are in accordance with our holding today: that, under Ten[794]*794nessee law, Cone’s vagueness challenge was not “waived,” but “previously determined.”
Therefore, although Cone failed to explicitly raise the vagueness challenge to the HAC aggravator, that claim was nonetheless implicitly decided on the merits by the Tennessee Supreme Court and it is a proper subject for federal habeas review.
IV.
Finally, we turn to the merits of Cone’s habeas claim that the HAC aggravator the jury considered in sentencing him to death is unconstitutionally vague, thus invalidating his sentence.
A.
Our standard of review is governed by the Antiterrorism and Effective Death Penalty Act of 1996 (AEDPA). When a petitioner’s claim has been adjudicated on the merits in a state court, a federal court may not grant a writ of habeas corpus with respect to such claim, unless the state court’s determination:
(1) resulted in a decision that was contrary to, or involved an unreasonable application of, clearly established Federal law, as determined by the Supreme Court of the United States; or
(2) resulted in a decision that was based on an unreasonable determination of the facts in light of the evidence presented in the State court proceeding.
28 U.S.C. § 2254(d) (West Supp.2003). A state court’s decision must be evaluated against the clearly established Supreme Court precedent at the time the petitioner’s conviction became final. Williams v. Taylor, 529 U.S. 362, 380, 120 S.Ct. 1495, 146 L.Ed.2d 389 (2000). Moreover, as we explained recently:
A state court decision is “contrary to” Supreme Court precedent “if the state court arrives at a conclusion opposite to that reached by [the Court] on a question of law,” or “if the state court confronts facts that are materially indistinguishable from a relevant Supreme Court precedent and arrives at a result opposite to” the Court’s decision. A state court decision involves an “unreasonable application” of clearly established Supreme Court precedent when it correctly identifies the governing legal standard but applies it to the facts of the case before it in an objectively unreasonable manner.
Alley v. Bell, 307 F.3d 380, 385 (6th Cm. 2002) (internal citation omitted) (quoting Williams, 529 U.S. at 405, 409-10, 120 S.Ct. 1495), cert. denied, — U.S. — —, 124 S.Ct. 99, 157 L.Ed.2d 72 (2003)
B.
At sentencing, the jurors were instructed that they could not impose the death penalty unless they unanimously found, beyond a reasonable doubt, at least one of eleven statutory aggravating factors, including whether “[t]he murder was especially heinous, atrocious, or cruel in that it involved torture or depravity of mind.” In a limiting instruction, the court then defined some of the terms of this aggravating factor:
“Heinous” means extremely wicked or shockingly evil.
“Atrocious” means outrageously wicked and vile.
“Cruel” means designed to inflict a high degree of pain, utter indifference to, or enjoyment of, the suffering of others, pitiless.
The jurors found that Cone’s crime was “especially heinous, atrocious, or cruel.” They did not add, on their verdict form, the words, “in that it involved torture or depravity of mind.” However, we do not [795]*795think that omitting that verbiage when announcing the verdict is of any constitutional significance.
Cone argues that the HAC aggravator is “clearly unconstitutional” based upon the holding of Godfrey v. Georgia, 446 U.S. 420, 100 S.Ct. 1759, 64 L.Ed.2d 398 (1980). Godfrey held that the Georgia statutory aggravator, “that the offense ‘was outrageously or wantonly vile, horrible or inhuman in that it involved torture, depravity of mind, or an aggravated battery to the victim,’ ” id. at 422, 100 S.Ct. 1759 (citation omitted), was unconstitutionally vague, because there was “nothing in these few words, standing alone, that implies any inherent restraint on the arbitrary and capricious infliction of the death sentence,” id. at 428, 100 S.Ct. 1759.
The State responds first, that the language of the Tennessee HAC aggravator, as further defined and limited by the trial court, is not the language found to be vague in Godfrey, and second, that the HAC aggravator in Cone’s case was not “contrary to ... clearly established” U.S. Supreme Court precedent as it stood at the time of Cone’s direct appeal. That precedent, the State argues, was established in Proffitt v. Florida, 428 U.S. 242, 96 S.Ct. 2960, 49 L.Ed.2d 913 (1976), decided eight years before Cone’s conviction became final, in which the Court held that Florida’s HAC aggravator was not unconstitutionally vague in light of the Florida courts’ narrowing construction that the term “heinous, atrocious, or cruel” means a “ ‘conscienceless or pitiless crime which is unnecessarily torturous to the victim.’ ” Id. at 255-56, 96 S.Ct. 2960 (citations omitted). This narrowing language is the identical language the Tennessee Supreme Court used in narrowing Tennessee’s HAC ag-gravator in State v. Dicks, 615 S.W.2d 126, 132 (Tenn.1981), a case decided three years before the court’s “implicit review” of Cone’s case. Moreover, the State argues, it must be presumed that the Tennessee Supreme Court evaluated the Cone jury’s reliance upon the HAC aggravator using the same narrowing construction adopted in Dicks. The State also reminds us that the U.S. Supreme Court held in Williams, 529 U.S. 362, 120 S.Ct. 1495, that the state court’s decision must be evaluated against the “clearly established” Supreme Court precedent at the time the petitioner’s conviction became final. Id. at 380, 120 S.Ct. 1495.
One thing is clear: No Supreme Court case has addressed the precise language at issue in this case. As we will show, the cases decided after Cone’s conviction became final indicate clearly that the language of the HAC aggravator the jurors used to sentence Cone to death — “especially heinous, atrocious, or cruel in that it involved torture or depravity of mind” — is unconstitutionally vague. Normally, post-Cone decisions would be immaterial, but, as will be seen, the Supreme Court’s fairly recent application of its doctrine of the “non-retroactivity” of new constitutional rules, in the context of an Eighth Amendment vagueness challenge to a death penalty instruction, makes several post-Cone Supreme Court decisions not only material, but controlling.
In 1988, in Maynard v. Cartwright, 486 U.S. 356, 108 S.Ct. 1853, 100 L.Ed.2d 372, a death penalty case from Oklahoma, the Supreme Court explicitly relied upon God-frey (the “outrageously or wantonly vile, horrible or inhuman” aggravator) to hold that Oklahoma’s HAC aggravator was unconstitutionally vague, id. at 363-64, 108 S.Ct. 1853, but implied that had Oklahoma’s HAC aggravator been further limited by a “torture or serious physical abuse” instruction, it might have been constitutional, id. at 365, 108 S.Ct. 1853. Nonetheless, two years later, in Shell v. [796]*796Mississippi, 498 U.S. 1, 111 S.Ct. 313, 112 L.Ed.2d 1 (1990) (per curiam), the Supreme Court announced that the “heinous, atrocious, or cruel” language, along with the same “limiting” definitions as were provided to the jury in Cone’s case, was unconstitutional. Id. at 1, 111 S.Ct. 313. The HAC aggravator in Shell, however, did not have the “torture or depravity” qualifier that is attached to the HAC ag-gravator in Cone’s case. In Walton v. Arizona, 497 U.S. 639, 110 S.Ct. 3047, 111 L.Ed.2d 511 (1990), overruled on other grounds by Ring v. Arizona, 536 U.S. 584, 122 S.Ct. 2428, 153 L.Ed.2d 556 (2002), the Court stated, “there is no serious argument that Arizona’s ‘especially heinous, cruel or depraved’ aggravating factor is not facially vague.” Id. at 654, 122 S.Ct. 2428.
Despite the confusion resulting from these cases (or perhaps because of it), the Supreme Court, in Stringer v. Black, 503 U.S. 222, 112 S.Ct. 1130, 117 L.Ed.2d 367 (1992), came at the subject from a different angle. It addressed the “new rule” non-retroactivity doctrine as respects Godfrey, the pre-Cone decision, and Maynard, the post-Cone decision.
[T]he language [in Maynard (“especially heinous, atrocious or cruel”) ] gave no more guidance than did the statute in Godfrey [ (“outrageously or wantonly vile, horrible or inhuman”) ]....
... 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 God-frey to the language before us in Maynard, we did not “brea[k] new ground.”
Id. at 228-29, 112 S.Ct. 1130 (quoting Butler v. McKellar, 494 U.S. 407, 412, 110 S.Ct. 1212, 108 L.Ed.2d 347 (1990)). The “break new ground” terminology refers to the rule announced in Teague v. Lane, 489 U.S. 288, 109 S.Ct. 1060, 103 L.Ed.2d 334 (1989), that if a decision announces a “new” constitutional rule, it is not to be applied retroactively to convictions that have already become final when the new decision is announced, subject to two narrow exceptions not applicable here. A “new [constitutional] rule” is one that “breaks new ground” or imposes new obligations on the states or federal government. Id. at 301, 109 S.Ct. 1060. “[A] case announces a new rule if the result was not dictated by precedent existing at the time the defendant’s conviction became final.” Id. (emphasis omitted).
Given this old rule/new rule definition, the language of Stringer, that Maynard did not “break new ground,” strongly suggests that the Supreme Court considers Godfrey to have clearly established the unconstitutionality of the HAC aggravator as early as 1980. Although Stringer dealt with a pre-AEDPA retroactivity issue, the Supreme Court in Williams v. Taylor, 529 U.S. 362, 120 S.Ct. 1495, 146 L.Ed.2d 389, explained that the “clearly established law” requirement codified the old rule/new rule doctrine of non-retroactivity that prevailed before AEDPA. Id. at 379-80, 412, 120 S.Ct. 1495; see also Harris v. Stovall, 212 F.3d 940, 944 (6th Cir.2000). Indeed, the Court cited Stringer as an example of the old rule/new rule doctrine codified by AEDPA’s “clearly established law” requirement. Williams, 529 U.S. at 412, 120 S.Ct. 1495.
Although none of these Supreme Court decisions is “on all fours” with the instruction in Cone’s case, in the final analysis, Stringer’s statement that Maynard’s invalidation of Oklahoma’s HAC aggravator was an “old rule” dictated by Godfrey, points ineluctably to the conclusion that Godfrey represents a “clearly established” Supreme Court precedent dictating that
[797]*797CONE v. BELL
Cite as 359 F.3d 785 (6th Cir. 2004)
Tennessee’s HAC aggravator is unconstitutionally vague. Although it is true that the HAC aggravator in Cone’s case contained the additional words “in that it involved torture or depravity of mind,” all of those words except “torture” have been held to be too vague, on the basis of God-frey. Since Maynard was dictated by Godfrey, it is difficult to imagine how any of the other cases addressing very minor variations on the instruction in Maynard and Cone would not also be dictated by Godfrey.
There remains, of course, the question whether the Tennessee Supreme Court’s narrowing construction of Tennessee’s HAC aggravator, announced in 1981 in Dicks, 615 S.W.2d at 132, that Tennessee’s HAC aggravator should be read as meaning “conscienceless or pitiless crime which is unnecessarily torturous to the victim,” the identical language that was approved in Proffitt, 428 U.S. at 255, 96 S.Ct. 2960, “saves” the HAC aggravator in Cone’s case.
[8] The State argues that if we are to indulge the fiction, discussed earlier, that the Tennessee Supreme Court “implicitly reviewed” Cone’s Eighth Amendment vagueness “challenge” to the HAC aggra-vator, a challenge Cone did not explicitly raise, we should also indulge the fiction that the court applied the “pitiless crime” narrowing construction it adopted for Tennessee’s HAC aggravator three years earlier in Dicks, 615 S.W.2d at 132. Although this “implicit narrowing construction” argument would provide a nice symmetry to the earlier “implicit review” argument, we think the two, on close consideration, are actually asymmetrical. Here’s why: The Tennessee court explicitly reviewed whether the HAC aggravator the jury found was supported by sufficient evidence, but in doing so, it did not apply, or even mention, any narrowing interpreta-
tion or cite to Dicks. Instead, the court simply, but explicitly, satisfied itself that the labels “heinous, atrocious, or cruel,” without more, applied to Cone’s crime. State v. Cone, 665 S.W.2d at 94-95.
[9] Therefore, we conclude that the Tennessee Supreme Court’s “implicit decision,” upon mandatory review of Cone’s death sentence, was that the HAC aggra-vator relied upon by Cone’s jury in imposing the death sentence was not arbitrary and, consequently, not unconstitutionally vague. We hold that this decision by the Tennessee Supreme Court was contrary to clearly established U.S. Supreme Court precedent as announced in Maynard and Shell, and made applicable to Cone’s case via the rule of retroactivity explained in Stringer.
We are not in the least comfortable with this “implicit review” doctrine, but it is a matter of Tennessee, not federal, law, and we know of no other way to read and understand what the Tennessee Supreme Court said in West.
y.
[10] We must now consider whether the jury’s erroneous application of two invalid aggravating factors was harmless error. The AEDPA standard of review does not apply to this question because no Tennessee court has considered this question. Thus, this is an independent harmless error inquiry, not a review of a state court’s harmless error inquiry.
Cone contends that this court is not empowered to perform an independent harmless error inquiry; rather, he argues, this court must grant habeas relief so that state courts can perform a new sentencing calculus. He insists that prior Sixth Circuit cases, Houston v. Dutton, 50 F.3d 381 (6th Cir.1995), and Coe v. Bell, 161 F.3d 320, are in conflict on this issue.
[798]*798In Coe v. Bell, we held that this court was “permitted to perform a harmless-error analysis” to determine whether a Tennessee jury’s reliance on the unconstitutional HAC aggravator required habeas relief. 161 F.3d at 334. We distinguished our previous decision in Houston v. Dutton, 50 F.3d at 387, on the ground that Houston had prohibited a federal habeas court from “re-weighing” but had not considered whether a federal habeas court could evaluate, in the first instance, the harmlessness of the jury’s reliance on an invalid aggravator.' Coe, 161 F.3d at 335. Thus, Coe drew a distinction between reweighing and harmless error analysis and held that a federal habeas court is permitted to undertake the latter.
The applicable harmless error standard is “whether the error ‘had substantial and injurious effect or influence in determining the jury’s verdict.’ ” Id. (quoting Brecht v. Abrahamson, 507 U.S. 619, 623, 113 S.Ct. 1710, 123 L.Ed.2d 353 (1993)). The Supreme Court elaborated on this standard to some extent in O’Neal v. McAninch, 513 U.S. 432, 115 S.Ct. 992, 130 L.Ed.2d 947 (1995), by explaining: “When a -federal judge in a habeas proceeding is in grave doubt about whether a trial error of federal law had substantial and injurious effect.or influence in determining the jury’s verdict, that error is not harmless.” Id. at 436, 115 S.Ct. 992 (internal quotation marks omitted); see also DePew v. Anderson, 311 F.3d 742, 751 (6th Cir.2002), cert. denied, — U.S. —, 124 S.Ct. 270, 157 L.Ed.2d 160 (2003), and cert. denied, — U.S. —, 124 S.Ct. 83, 157 L.Ed.2d 250 (2003).
In Coe v. Bell, 161 F.3d at 335, we considered whether the jury’s reliance on an unconstitutionally vague HAC aggravating factor had a “substantial and injurious effect” on the sentence. We concluded that it did not because the jury’s sentencing verdict form indicated that “the jury [had] ignored the problematic ‘depravity’ factor and limited its finding to the appropriately narrowing ‘torture’ factor.” Id. at 336. Thus, the error was harmless because the jury, effectively, had “channeled” its own discretion despite the failure of the instructions to do so. Id.
In Abdur’Rahman v. Bell, 226 F.3d 696 (6th Cir.2000), cert. denied, 534 U.S. 970, 122 S.Ct. 386, 151 L.Ed.2d 294 (2001), we again considered the harmfulness of the jury’s reliance on the unconstitutionally vague HAC aggravator. We remarked that “removing one aggravating circumstance from the sentencing calculus in a weighing state normally would require a re-weighing of the aggravating and mitigating factors.” Id. at 711. We determined, however, that the jury’s reliance on the HAC aggravator was harmless because, “even if the heinous, atrocious, or cruel aggravator is removed from the calculus, there is no mitigating evidence to weigh against the remaining ... aggrava-tors.” Id.
In this case, when the jury made its sentencing determination it found four aggravating circumstances ((1) HAC; (2) great risk of death to others; (3) prior violent felonies; and (4) murder for purpose of avoiding arrest/prosecution), and weighed those against the mitigating evidence offered by the defense. This balancing process was infected by the weight of .two invalid aggravating factors: (1) HAC, which was unconstitutionally vague, and (2) great risk of death to others, which was not supported by sufficient evidence.
The prosecutor specifically emphasized the HAC aggravator during his closing arguments at the sentencing phase of the trial. In contrast to Coe, 161 F.3d at 336, the jury here did not “ehannel[ ]” its discretion by ignoring the vagueness inherent in. the HAC aggravator. Moreover, al[799]*799though the defense here offered no mitigating evidence at sentencing, the Supreme Court stated in Bell v. Cone, 535 U.S. at 699, 122 S.Ct. 1843, that the defense put before the jury “the most compelling mitigating evidence in the case” during the guilt phase. The Court’s observation thus distinguishes this case from Abdur’Rahman, in which we concluded that the HAC aggravator, if unconstitutionally vague, did not substantially affect the sentence due to the total absence of mitigating evidence.
The second invalid aggravator, “great risk of death to others,” was found by the jury despite insufficient evidence, State v. Cone, 665 S.W.2d at 95, even though the prosecutor did not request the jury to find this aggravator. One could argue that this aggravator must have influenced the sentencing decision, since the jury found it without sufficient evidence and without being asked to do so by the prosecution. In any event, we conclude that these two invalid aggravators, together, if not individually, “ ‘had substantial and injurious effect or influence in determining’ ” the jury’s sentence. Brecht, 507 U.S. at 631, 113 S.Ct. 1710 (citation omitted). The error, therefore, is not harmless.
VI.
For the foregoing reasons, the district court’s decision is REVERSED as to the petitioner’s sentence. We REMAND to the district court with instructions to issue a writ of habeas corpus vacating the petitioner’s death sentence due to the jury’s weighing of an unconstitutionally vague aggravating factor at sentencing, unless the State conducts a new penalty phase proceeding within 180 days of remand.