In 1995, the legislature amended the statutory scheme to  [*10]  provide for a weighing process by the jury at the penalty phase. See Public Acts 1995, No. 95-19, § 1 (P.A. 95-19). Under the statutory scheme as amended in 1995, the burdens of persuasion regarding proof of the existence of aggravating and mitigating factors remain the same. The state must still establish the existence of an aggravating factor by proof beyond a reasonable doubt, and the defendant must still establish the existence of a mitigating factor by a preponderance of the evidence. Furthermore, the role of a statutory mitigating factor remains the same: proof of its existence will preclude the imposition of the death penalty and mandate a sentence of life imprisonment without the possibility of release. General Statutes (Rev. to 1997) § 53a-46a (g) and (h); see footnote 4 of this opinion.

Under the 1995 amended scheme, however, the role of the nonstatutory mitigating factors has changed. Pursuant to General Statutes (Rev. to 1997) § 53a-46a (e), the jury must return "a special verdict setting forth . . . whether any aggravating factor or factors outweigh any [nonstatutory] mitigating factor or factors," and, pursuant to General Statutes (Rev. to 1997) § 53a-46a  [*11]  (f), if the "mitigating factors . . . are outweighed by . . . [the] aggravating factors . . . the court shall sentence the defendant to death." See footnote 4 of this opinion. Thus, under these provisions, the jury must weigh the aggravating factors proven against the nonstatutory mitigating factors proven, and if the aggravating factors outweigh the mitigating factors, the court must impose the death sentence. The statute is silent, however, with respect to a burden of persuasion on the weighing process itself.

The defendant claims that the applicable burden of persuasion on the weighing process is the traditional criminal burden of beyond a reasonable doubt. n8 Before considering the defendant's claim, we must first identify it, because it is subject to two different interpretations: one interpretation focuses on measuring the balance between the aggravating factors and the mitigating factors; and the other interpretation focuses on the level of certitude required of the jury in determining that the aggravating factors outweigh the mitigating factors. In other words, we first must clarify whether the defendant claims that: (1) in performing the weighing process,  [*12]  the jury must be persuaded that the aggravating factors outweigh the mitigating factors by some quantum or amount measured by the "beyond a reasonable doubt" standard; or (2) in performing the weighing process, the jury must be persuaded beyond a reasonable doubt that the aggravating factors outweigh the mitigating factors by any degree or amount. Under the first interpretation, the jury must be persuaded that the balance of the aggravating factors against the mitigating factors must tip greatly--in the words of the defendant's request to charge, "substantially"; see footnote 8 of this opinion;--in favor of the aggravating factor such that the quantitative difference between the two factors would be aptly described as "beyond a reasonable doubt." Under the second interpretation, the jury need only determine that the aggravating factor is greater in some degree or amount than the mitigating factor, but, in arriving at that determination, it must be persuaded by a level of certitude of beyond a reasonable doubt. Although it is not altogether clear, a fair reading of the defendant's briefs is that he claims that: (1) the first interpretation is constitutionally required by our state constitution;  [*13]  but (2) even if the constitutional claim fails, the second interpretation should be adopted to fill a gap left by the legislature on the burden of persuasion applicable to the ultimate weighing decision.

Against this background, we consider the defendant's challenge to the constitutionality, under our state constitution, of § 53a-46a (e) and (f). Specifically, the defendant claims that, under our state due process clauses, embodied in article first, §§ 8 and 9, of the state constitution, n9 in order for the death penalty to be imposed, the jury must be instructed that the aggravating factors outweigh the mitigating factors beyond a reasonable doubt. More specifically, the defendant claims that "[the] jury was not instructed about the standard of certainty that the jury needed to employ when deciding whether or not the aggravating [factor] outweighed the mitigating factors. The defendant maintains that this absence of a statutory standard [of certitude] means that the legislature has left it to the courts to provide an appropriate standard. . . . The proper standard of certitude for this question of first impression should be that, in order for there to be a death sentence, the proven aggravating factor(s) must outweigh the proven mitigating factor(s) beyond a reasonable doubt."

* *  *

To summarize then, we conclude that our state constitution does not require that the jury, in deciding the balance between the aggravating factors and the mitigating factors, determine that that balance be anything other than is described by the terms, "greater than," "weightier than," "more compelling than," or "more significant than," in any degree or amount. The balance constitutionally need not be described as "substantially more than," or as "beyond a reasonable doubt." As we explain in part I F of this opinion, however, the jury's subjective level of certitude in reaching the determination that the aggravating factors outweigh the mitigating factors, as described previously, must be that level of certitude defined by the phrase, "beyond a reasonable doubt."
 
F
 
The  [*78]  Appropriate Burden of Persuasion on the Weighing Process
 
Having concluded that there is no state constitutional requirement that the aggravating factors outweigh the mitigating factors beyond a reasonable doubt, we are not, however, finished with our task. We further conclude that, despite this constitutional conclusion, without an appropriate burden of persuasion placed on the level of certitude that the jury must have in making its weighing determination, there would be a potentially significant state constitutional question about our capital sentencing scheme. Therefore, without deciding and in order to avoid any such state constitutional question, we conclude n31 that the jury must be instructed that, in arriving at its judgment that the aggravating factors outweigh the mitigating factors by any degree or amount, it must be persuaded that death is the appropriate penalty in the case, and that its level of certitude in arriving at that ultimate weighing judgment must be beyond a reasonable doubt. n32 See State v. Snook, 210 Conn. 244, 251, 555 A.2d 390 (1989) ("this court should try, whenever possible, to construe statutes to avoid a constitutional  [*79]  infirmity" [internal quotation marks omitted]), cert. denied, 492 U.S. 924, 109 S. Ct. 3258, 106 L. Ed. 2d 603 (1989).

Informing our conclusion regarding the required burden of persuasion for the jury in its performance of the weighing process, are three factors, namely: (1) the nature of the death penalty; (2) an overarching need for reliability and consistency in the imposition of the death penalty; and (3) the nature of the jury's determination to render a verdict requiring the penalty. These three factors are directly relevant to an analysis under In re Winship, supra, 397 U.S. 370-72, of the appropriate burden of persuasion because they indicate that the decision to sentence a defendant to death is of the highest importance and that a jury cannot be faced with a more solemn task. As a foundation for our conclusion that, in order to avoid potentially significant constitutional questions, there must be a burden of persuasion of beyond a reasonable doubt on the jury's determination to impose the death penalty, we focus first on those three factors.

Death is different. "The penalty of death differs from all other forms of criminal punishment, not in degree but in kind. It is unique in its total irrevocability. It is unique in its rejection of rehabilitation of the convict as a basic  [*82]  purpose of criminal justice. And it is unique, finally, in its absolute renunciation of all that is embodied in our concept of humanity." Furman v. Georgia, 408 U.S. 238, 306, 92 S. Ct. 2726, 33 L. Ed. 2d 346 (1972) (Stewart, J., concurring). "The imposition of death by public authority is . . . profoundly different from all other penalties . . . ." Lockett v. Ohio, 438 U.S. 586, 605, 98 S. Ct. 2954, 57 L. Ed. 2d 973 (1978). "The penalty of death is qualitatively different from a sentence of imprisonment, however long. Death, in its finality, differs more from life imprisonment than a 100-year prison term differs from one of only a year or two." Woodson v. North Carolina, 428 U.S. 280, 305, 96 S. Ct. 2978, 49 L. Ed. 2d 944 (1976).

Moreover, an overarching principle of both federal and our state constitutional death penalty jurisprudence is that, "because of that qualitative difference, there is a corresponding difference in the need for reliability in the determination that death is the appropriate punishment in a specific case." Id. The eighth amendment requires "heightened reliability . . . in the determination whether  [*83]  the death penalty is appropriate . . . ." Sumner v. Shuman, 483 U.S. 66, 72, 107 S. Ct. 2716, 97 L. Ed. 2d 56 (1987). Under our prior, nonweighing statute, we held that the finding of an aggravating factor met the federal constitutional "prerequisite of consistency and reliability by guiding the capital sentencer's discretion" at the eligibility phase, and that requiring the death penalty only where no mitigating factor was proven met the federal constitutional "individualization prerequisite by requiring the sentencer to consider any relevant mitigating information so as to enable the sentencer to make the reasoned moral judgment that death is the appropriate punishment in a particular case." State v. Ross, supra, 230 Conn. 238-39. We have also held that "the due process clauses of our state constitution incorporate the principles underlying a constitutionally permissible death penalty statute that the United States Supreme Court has articulated in cases such as California v. Brown, [479 U.S. 538, 541, 107 S. Ct. 837, 93 L. Ed. 2d 934 (1987)], Eddings v. Oklahoma, [455 U.S. 104, 110-12, 102 S. Ct. 869, 71 L. Ed. 2d 1 (1982)],  [*84]  and Lockett v. Ohio, supra, 438 U.S. 602-605. These principles require, as a constitutional minimum, that a death penalty statute . . . must channel the discretion of the sentencing judge or jury so as to assure that the death penalty is being imposed consistently and reliably . . . ." (Emphasis added.) State v. Ross, supra, 252. In addition, of course, the death penalty represents the most extreme form of power exercised by the state over the individual.

Furthermore, precisely because of the enormous qualitative difference between death and all other forms of punishment, the nature of the jury's determination to impose it is different from all other determinations that juries make in our state's legal system. On a strictly procedural level, a capital penalty phase proceeding differs from all other sentencing proceedings in that: (1) it is the only such proceeding in which a jury, rather than the court, may in effect impose the sentence; see State v. Breton, 235 Conn. 206, 246, 663 A.2d 1026 (1995); (2) it is the only such proceeding in which there must be a full, trial-like, evidentiary hearing; and (3) it is the only such proceeding  [*85]  in which the state must establish the foundation of its case for sentencing--in the sense of establishing the aggravating factor--by proof beyond a reasonable doubt. Furthermore, as a practical matter, in many capital cases the question of whether the defendant should suffer the death penalty, as opposed to whether he or she in fact committed a capital felony, is the principal and overarching question in the case. Indeed, in the present case, it was the only question. On a more fundamental level, the "'task . . . of determining whether a specific human being should die at the hands of the State'"; State v. Ross, supra, 230 Conn. 241, quoting Caldwell v. Mississippi, 472 U.S. 320, 329, 105 S. Ct. 2633, 86 L. Ed. 2d 231 (1985); necessarily calls upon the intellectual, moral and emotional resources of the jurors in a way that far exceeds any factual determination of guilt or innocence. It requires the jury to make "a reasoned moral and individualized determination" regarding the imposition of the death penalty. State v. Ross, supra, 253. It is not hyperbole to say that making "the choice is between life and death"; Lockett v. Ohio, supra, 438 U.S. 605;  [*86]  is the most serious decision that our legal system requires a jury to make. Indeed, we have described it as an "awesome decision . . . ." State v. Ross, supra, 253.

* * *
Under the current statute . . . . once the state has proved at least one aggravating factor (the second tier) and the defendant has proved at least one mitigating factor (the third tier), the jury must then weigh the one against the other (the fourth tier). This change in our capital sentencing scheme has effectively expanded the selection phase to include, in addition to the determination of whether  [*89]  the defendant has established mitigation, the weighing of the aggravating factors against the mitigating factors. It has also resulted in a significant gap in the sentencing scheme--namely, unlike our former, nonweighing statute, the current sentencing statute does not require the jury to make its ultimate determination--that the aggravating factors outweigh the mitigating factors, and that, therefore, death is the appropriate sentence--by a level of certitude beyond a reasonable doubt. Indeed, because the legislature was silent as to the required level of certitude imposed on the jury's weighing determination, there is a statutory lacuna, which, we are persuaded, should be filled.

We recognize that, in effect, by imposing the reasonable doubt standard on the jury's level of certitude in order to fill the gap in the weighing statute, we are channeling juror discretion during the selection phase. The United States Supreme Court has accorded "differing constitutional treatment" to the eligibility and selection phases; Buchanan v. Angelone, 522 U.S. 269, 275, 118 S. Ct. 757, 139 L. Ed. 2d 702 (1998); emphasizing the need to channel sentencer discretion during the  [*90]  eligibility phase rather than the selection phase. See, e.g., id., 275-76; Tuilaepa v. California, supra, 512 U.S. 971-73.

In our case law, we have, in fact, recognized this development in the Lockett-Eddings line of cases. See State v. Cobb, supra, 251 Conn. 483-85, quoting Buchanan v. Angelone, supra, 522 U.S. 275-77. In Ross, however, when we alluded to the federal standard in the context of our discussion of the defendant's state constitutional claims, we specifically stated that the federal standards set a state "constitutional minimum . . . ." State v. Ross, supra, 230 Conn. 252. Indeed, we acknowledged, in regard to the individualization requirement, at the selection phase, that "although this [requirement] demands that the sentencer must be able to consider and give effect to any mitigating evidence relevant to a defendant's background and character or the circumstances of the crime . . . the federal constitution does not require unfettered sentencing discretion . . . . States are free to structure and shape consideration of mitigating evidence in an effort to achieve  [*91]  a more rational and equitable administration of the death penalty." (Citations omitted; emphasis added; internal quotation marks omitted.) Id., 234. This, at least implicitly, left open the question whether, under other circumstances, such as the present case, our state constitution would require channeling jury discretion during the selection phase.

Furthermore, in Ross, we recognized the dual constitutional requirements addressed by federal death penalty jurisprudence, namely, "on the one hand, [channeling sentencer discretion] so as to assure that the death penalty is being imposed consistently and reliably and, on the other hand, [permitting the sentencer] to consider, as a mitigating factor, any aspect of the individual defendant's character or record as well as the circumstances of the particular offense." (Emphasis added.) Id., 252. In explaining the two requirements, we stated that the first requirement "requires death penalty statutes to be structured so that the death penalty is imposed in a consistent and reliable manner. In deciding to authorize capital punishment, a state has a constitutional responsibility to tailor and apply  [*92]  its law in a manner that avoids the arbitrary and capricious infliction of the death penalty [including] defining the crimes for which death may be the sentence in a way that obviates standardless sentencing discretion." (Emphasis added; internal quotation marks omitted.) Id., 231-32. In regard to the second requirement, we stated that the sentencer must "not be precluded from considering, as a mitigating factor, any aspect of a defendant's character or record and any of the circumstances of the offense that the defendant proffers as a basis for a sentence less than death." (Emphasis in original; internal quotation marks omitted.) Id., 233. Thus, in our analysis of the second requirement, we emphasized the constitutional necessity of limiting "a State's ability to narrow a sentencer's discretion to consider relevant evidence that might cause it to decline to impose the death sentence." (Emphasis in original; internal quotation marks omitted.) Id., 233-34.

Put another way, Ross may be read as standing for the proposition that, under our state constitution, our overarching concern for consistency and reliability in the imposition  [*93]  of the death penalty extends to the ultimate decision of whether to impose or to decline to impose that penalty. Therefore, because the issue in the present case directly involves the decision of whether to impose or to decline to impose the death penalty, Ross' requirement of reliability raises the potential state constitutional question of whether the sentencer's ultimate weighing decision, which may result in the imposition of the death penalty, must be channeled by a sufficiently high burden of persuasion.

Therefore, in light of and in order to avoid this significant potential state constitutional question, and in light of the three factors discussed previously--namely, (1) the unique and irrevocable nature of the death penalty, (2) the overarching need for reliability and consistency in the imposition of the death penalty, and (3) the awesome and wrenching nature of the jury's determination to render a verdict requiring the death penalty--we conclude that the highest burden of persuasion should be imposed on the jury's weighing process. Requiring a high degree of persuasion on the weighing process would convincingly avoid any potential state constitutional question. It would  [*94]  also give due deference to the unique and irrevocable nature of the death penalty, and to the consequently overarching need for reliability in the imposition of such a penalty, and it would give due deference to the awesome and wrenching nature of the jury's task in arriving at its moral and reasoned judgment that the death penalty should be imposed. n34 We further conclude, therefore, that the most appropriate burden of persuasion for that process is that of beyond a reasonable doubt. If a jury is required to conclude beyond a reasonable doubt that a defendant is guilty of a capital offense, and to conclude that an aggravating factor has been established, it should also be required to conclude by the same high burden of persuasion that the death penalty is the appropriate penalty in the case. Thus, just as we did in State v. Daniels, supra, 207 Conn. 374, where we filled gaps left by the legislature in defining the burdens of persuasion on the proof of an aggravating factor and mitigating factor, we fill the gap left by the legislature in defining the burden of persuasion on the weighing process by imposing, on the most important question that our legal  [*95]  system entrusts to the jury, namely, whether the defendant shall live or die, the highest burden of persuasion that our legal system recognizes.

Noted above.