MARSHALL, J.

On December 10, 1975, a Suffolk County jury convicted the defendant, Robert Anderson, of murder in the first degree (by reason of deliberate premeditation or felony-murder), armed robbery, and the unlawful carrying of a firearm. On December 18, 1975, the defendant filed a notice of appeal, but no further steps were taken in connection with his appeal. On May 17, 1977, the trial judge dismissed the appeal. On September 17, 1996, a single justice of this court allowed the defendant's petition to reinstate his appeal pursuant to G.L.c. 211, § 3.

The defendant argues that the trial judge's instructions on reasonable doubt impermissibly reduced the Commonwealth's burden of proof, and that his armed robbery conviction is duplicative of his murder conviction. The defendant also asks that, pursuant to G.L.c. 278, § 33E, we order a new trial or reduce the verdict. We conclude that the trial judge properly instructed the jury on proof beyond a reasonable doubt, and that there is no basis to exercise our power under G.L.c. 278, § 33E. We also conclude that the defendant's armed robbery conviction may have been duplicative of his conviction of murder in the first degree, and we vacate his conviction of armed robbery.

We summarize the facts as the jurors could have found them, in the light most favorable to the Commonwealth. Commonwealth v. Sanna, 424 Mass. 92, 93 (1997). On December 10, 1974, at approximately 4 P. M., the victim's fifteen year old son was tending the cash register in the victim's shoe repair shop in the Roxbury section of Boston when the defendant, one Jerry Funderberg, and a man known as "Pabst" entered the shop. In response to a request for change from one of the men, the victim's son opened the register, whereupon "Pabst" reached in and removed money from the cash drawer. The victim emerged from the rear of the store. The defendant and Funderberg both had guns. As the victim walked toward them, they both fired several shots, fatally wounding the victim. The three men then fled to a nearby housing project.

An apartment at the housing project was used as a "shooting gallery" where customers could pay a fee to use heroin. The three men arrived there out of breath, some time after 4 P. M. Both the defendant and Funderberg were carrying pistols. The three men argued over the amount of money they had taken, "Pabst" purchased some heroin from a seller in a different apartment in the building, and all three men then retreated into a back room of the apartment. The police arrived while the men were still there, but left without searching the apartment when the proprietor of the "shooting gallery" asked them for a search warrant. Several days later, Funderberg boasted to the proprietor that he had shot the victim.

On the evening of the robbery, the defendant returned a .32 caliber revolver to Wilbur Billings that he had borrowed earlier that same day. Three of the chambers were empty. The defendant explained to Billings that he had used the bullets when "a dude was coming at him with a piece and he wasn't about to let the dude hurt him so he had to cap him."

On March 2, 1975, the police arrested the defendant. That same day, and again on March 3, the defendant made statements to the police that were recorded, in which he confessed to his involvement in the robbery and the shooting of the victim. Although he admitted to firing three shots at the victim, he said that he had intentionally aimed his weapon to miss the victim.

1. Jury instructions on reasonable doubt. The defendant argues that errors in the judge's instruction, quoted in the margin, improperly lowered the Commonwealth's burden of proof in violation of his due process rights under the Fifth and Fourteenth Amendments to the United States Constitution and art. 12 of the Massachusetts Declaration of Rights. Specifically, the defendant claims that the judge failed to express the "near certainty" required for conviction, erroneously used the phrase "doubt based on reason," and improperly defined "reasonable doubt" in negative terms without balancing the definition with positive terms. At trial the defendant did not object to the portion of the charge regarding reasonable doubt; we review the challenged instruction under G.L.c. 278, § 33E, to determine whether the instruction on reasonable doubt created a substantial likelihood of a miscarriage of justice. Commonwealth v. Torres, 420 Mass. 479, 483 (1995).

When we review a jury instruction to determine whether the charge unconstitutionally diminishes the Commonwealth's burden of proof, we consider "whether a reasonable juror could have used the instruction incorrectly." Commonwealth v. Rosa, 422 Mass. 18, 27 (1996). In making that determination, we review the charge as a whole. See id.; Commonwealth v. Pinckney, 419 Mass. 341, 342 (1995), quoting Victor v. Nebraska, 511 U.S. 1, 5 (1994) ("taken as a whole, the instructions [must] correctly conve[y] the concept of reasonable doubt to the jury"); Commonwealth v. Libby, 405 Mass. 231, 234 (1989) (defendant's claim is not supported "by a reading of the charge as a whole"); Commonwealth v. Lanoue, 392 Mass. 583, 591 (1984), S. C., 400 Mass. 1007 (1987), and 409 Mass. 1 (1990) ("propriety of [reasonable doubt] instructions must be determined from a consideration of the charge as a whole and not from a consideration of isolated portions"). Reviewing the jury charge in its entirety, we are satisfied that in this case the judge properly instructed the jury on reasonable doubt.

First, we do not agree that the trial judge impermissibly failed to instruct the jury that a "near certitude" was required for conviction. See Jackson v. Virginia, 443 U.S. 307, 315 (1979). According to the defendant, the "heart" of the traditional charge stemming from Commonwealth v. Webster, 5 Cush. 295, 320 (1850), is the language requiring that the Commonwealth prove its case to a "moral certainty." Where we have approved of alternative jury instructions, he says, other language approximating "near certitude" has been substituted.

The reasonable doubt standard defies easy explication, and no precise formulation is required to advise the jury of the Commonwealth's burden of proof. See Commonwealth v. Pinckney, supra at 342, quoting Victor v. Nebraska, supra at 5 (Federal Constitution "does not require that any particular form of words be used in advising the jury of the government's burden of proof . . ."). And we have never held that the omission of the Webster charge or its equivalent constitutes a violation of a defendant's due process rights. Commonwealth v. Randolph, 415 Mass. 364, 367 (1993) ("we have never required conformity to Webster . . . though we recommend it"). Here, the judge instructed the jury that they were to be satisfied beyond a reasonable doubt as to every essential element of each of the indictments, impressed upon the jury their duty to deliberate with great care, and informed them that they would be "required to acquit" the defendant unless they found with respect to every essential element of any charge that they had no doubt based on reason. This was adequate to convey to the jury the measure of certainty required to find the defendant guilty.

Second, the defendant argues that the phrases "doubt based on reason" and "doubt founded upon reason" impermissibly shifted the burden of proof to the defendant; this language, he says, erroneously required him to demonstrate the existence of a reason leading to doubt. We do not agree. The Supreme Court has stated: "A `reasonable doubt,' at a minimum, is one based upon `reason'," Jackson v. Virginia, 443 U.S. 307, 317 (1979), and that it is a doubt "based on reason which arises from the evidence or lack of evidence." Johnson v. Louisiana, 406 U.S. 356, 360 (1972). We see no reason to conclude that an instruction that reasonable doubt is a doubt based on or founded upon reason causes any burden shifting. We distinguish cases criticizing language defining reasonable doubt as doubt based upon a reason rather than doubt based upon reason, as charged in this case. See, e.g., Commonwealth v. Lanoue, 392 Mass. 583, 591 (1984) ("phrase, `[a] doubt for which a good reason can be given,' should not have been used"); Commonwealth v. Bjorkman, 364 Mass. 297, 309 (1973) ("the phrase `doubt based upon a reason,' even if of doubtful propriety standing alone, could not have caused any prejudicial shifting of the Commonwealth's burden of proof in the minds of the jurors"). Language requiring a reason may be burden-shifting, for it may remove the jurors' attention from the sufficiency of the evidence and suggest that they must find an articulable reason to acquit. See Commonwealth v. Bjorkman, supra at 308. This concern does not arise when the jury is properly instructed that reasonable doubt is doubt based upon reason.

Last, relying on Commonwealth v. Watkins, 377 Mass. 385, 388, cert. denied, 442 U.S. 932 (1979), the defendant argues that the instruction on reasonable doubt was erroneous because it "included negative formulations of reasonable doubt but failed to include positive formulations," creating an "unbalanced" charge; he says that we have declined to reverse a conviction only when the unbalanced instruction included a proper definition of reasonable doubt. We are not persuaded. Here, the judge gave the jury an adequate definition of reasonable doubt; because the defendant's argument is predicated upon his claim that the charge did not include a proper definition of reasonable doubt, it fails. We are satisfied that, when read as a whole, the charge properly defined proof beyond a reasonable doubt.

2. Relief under G.L.c. 278, § 33E. In accordance with our statutory obligations, we review the record as a whole and consider whether there is reason to conclude that the affirmance of the conviction would give rise to a substantial likelihood of a miscarriage of justice. We find no reason to conclude there is any such likelihood.

We do comment on one aspect of the trial that has been raised by the Commonwealth, the omission of an instruction to the jury to consider the voluntariness of the defendant's statements to the police in accordance with our "humane practice" doctrine. The defendant never raised the issue at trial and has not done so on appeal. We nevertheless review the record to determine whether this omission was error and whether it gave rise to a substantial likelihood of a miscarriage of justice. See Commonwealth v. Parham, 390 Mass. 833, 841 (1984). We conclude that the judge properly did not submit the voluntariness of the defendant's confessions to the jury for consideration.

Under our "humane practice" doctrine, where, as here, a trial judge has made an initial determination concerning the voluntariness of a confession, he "must instruct the jury to pass on the voluntariness of the confession if voluntariness is a live issue at trial." Id.; Commonwealth v. Alicea, 376 Mass. 506, 523 (1978). We think that such consideration by the jury was not compelled in this case because we conclude that voluntariness was not a live issue at trial; there was no evidence before the jury that could have supported the conclusion that the confessions were not voluntary. See Commonwealth v. Parham, supra at 841-842; Commonwealth v. Vazquez, 387 Mass. 96, 102 (1982); Commonwealth v. Cole, 380 Mass. 30, 40 (1980). Although there was conflicting testimony on the voluntariness of his confession by the defendant himself during voir dire, this evidence was never before the jury. Raising the issue of voluntariness before the trial and invoking the right to a voir dire proceeding alone does not give rise to the obligation of the judge to give the "humane practice" instructions sua sponte. See Commonwealth v. Parham, supra; Commonwealth v. Alicea, supra at 523. Contrast Commonwealth v. Harris, 371 Mass. 462, 472 (1976); Commonwealth v. Vazquez, supra at 102-103; Commonwealth v. Cole, supra at 40-41. In this case, the question of voluntariness was not raised "with sufficient point to require an express admonition to the jury by the Court" on its own motion. Commonwealth v. Alicea, supra at 523. We find no reason to exercise our authority under G.L.c. 278, § 33E, either to order a new trial or to reduce the verdict to murder in the second degree.

3. Duplicative conviction. The defendant argues that his conviction for armed robbery must be vacated because it is duplicative of the conviction for murder in the first degree. This issue is not contested by the Commonwealth. When the possibility exists that a jury may have reached a verdict of murder on the basis of a felony-murder theory, a separate conviction and sentence for the underlying felony cannot stand. See Commonwealth v. Raymond, 424 Mass. 382, 396-397 (1997); Commonwealth v. Bennett, 424 Mass. 64, 69 (1997). The jury were instructed on murder in the first degree on both deliberate premeditation and felony-murder theories, and the jury returned a general verdict of guilty without specifying under which theory they were convicting the defendant. Because the verdict may have been founded on the felony-murder theory of culpability, we order that the judgment of conviction of armed robbery be vacated.

We affirm the conviction of murder in the first degree. We order that the judgment of conviction of armed robbery and the sentence imposed thereon be vacated and remand the matter to the Superior Court for entry of judgment consistent with this opinion.

So ordered.