(concurring in part and dissenting in part, with whom Ireland, C.J., and Cordy, J., join). I agree that the evidence presented to the grand jury supports the indictment for murder in the second degree. I do not agree with Justice Gants, who would hold that in all cases where the Commonwealth seeks an indictment for murder and there is substantial evidence of mitigating circumstances or defenses (except lack of criminal responsibility), the grand jury must be instructed on the effect of mitigating circumstances and defenses. In my opinion the usual instructions on the elements of murder are all that need to be given. I agree with so much of Justice Lenk’s analysis that reaffirms our jurisprudence that generally rejects any requirement that the Commonwealth present evidence to the grand jury concerning mitigating circumstances or defenses, or that the grand jury be instructed as to such mitigating circumstances or defenses absent a specific request from the grand jury. I disagree with Justice Lenk’s analysis that an exception to the general rule must be made where a prosecutor seeks to indict a juvenile for murder because of special circumstances arising from the juvenile’s status. In such cases Justice Lenk would require the grand jury to be instructed as to the effect of any mitigating circumstances or defenses (except lack of criminal responsibility) that are raised by the evidence. See ante at 832-833 & note 29 (Lenk, J., concurring). I will address first the opinion of Justice Gants, then the opinion of Justice Lenk.
“The grand jury have the dual function of determining whether there is probable cause to believe a crime has been committed and of protecting citizens against unfounded criminal *845prosecutions.” Lataille v. District Court of E. Hampden, 366 Mass. 525, 532 (1974). We have never defined the term “unfounded criminal prosecution.” We have said only that in order to protect against unfounded criminal prosecutions, “at the very least the grand jury must hear sufficient evidence to establish the identity of the accused, . . . and probable cause to arrest him” (citations omitted). Commonwealth v. McCarthy, 385 Mass. 160, 163 (1982).
The grand jury are a body whose function is “limited.” Commonwealth v. Wilcox, 437 Mass. 33, 39 (2002). The grand jury are “an investigatory and accusatory body only. It cannot and does not determine guilt.” Id., quoting Brunson v. Commonwealth, 369 Mass. 106, 120 (1975). See Commonwealth v. Geagan, 339 Mass. 487, 497, cert. denied, 361 U.S. 895 (1959). The nature of the grand jury is largely “historical and practical.” Commonwealth v. McLeod, 394 Mass. 727, 733, cert. denied sub nom. Aiello v. Massachusetts, 474 U.S. 919 (1985). Generally a court will not review an irregularity before a grand jury that can be addressed and corrected at a subsequent trial before a petit jury. See, e.g., Commonwealth v. Knapp, 9 Pick. 495, 495-496 (1830). See also Commonwealth v. McLeod, supra; Commonwealth v. Geagan, supra at 499. Review of grand jury proceedings is disfavored because “the delays and complexity of criminal trials would be greatly increased, and no correspondingly useful purpose would be served.” Id., quoting Commonwealth v. Woodward, 157 Mass. 516, 519 (1893). See Commonwealth v. Noble, 429 Mass. 44, 48 (1999); Tucker’s Case, 8 Mass. 286, 287 (1811).
Examples of this “practical” view of grand jury proceedings are as follows. A grand juror need not have heard all the evidence presented against a defendant in order to vote to return an indictment. See Commonwealth v. Wilcox, supra at 34. A grand jury need not be entirely free of bias or prejudice, and may act on their own personal knowledge. Commonwealth v. McLeod, supra at 732-735. An indictment may be based on hearsay, even “solely on hearsay,” Commonwealth v. O’Dell, 392 Mass. 445, 450-451 (1984), although direct testimony is preferred. See Commonwealth v. St. Pierre, 377 Mass. 650, 655-656 (1979). Generally, a court does not inquire into the adequacy or *846competency of the evidence on which probable cause is based, as such matters may be addressed in the trial court. See Commonwealth v. Salman, 387 Mass. 160, 166 (1982); Commonwealth v. McCarthy, supra at 160-161; Commonwealth v. Geagan, supra at 495-499.
There are certain exceptions to the general rule of limited review of a grand jury’s proceedings. This court has indicated that an indictment might be set aside, usually without prejudice,1 where a defendant makes a showing that the integrity of the grand jury proceedings was impaired. This is a “case by case” inquiry. See Commonwealth v. Mayfield, 398 Mass. 615, 620 (1986). Impairment is usually based on the conduct of the prosecutor. For example, an indictment may be dismissed if false or deceptive evidence were presented knowingly or recklessly to the grand jury and such evidence probably influenced the grand jury’s decision to indict. See id. at 621-622. See also Commonwealth v. Salman, supra at 167 (“If it becomes known to the prosecution that false testimony was knowingly used to obtain an indictment, it is the duty of the prosecutor to advise the court and request a dismissal of the indictment”). Similarly withholding an exculpatory2 portion of a defendant’s statement and repeating the inculpatory portion to the grand jury in a way that distorted its import may be so unfair and misleading that an indictment may not be allowed to stand where the distortion probably affected the decision to indict. See Commonwealth v. O’Dell, supra at 446-447. An indictment also may be dismissed if known exculpatory evidence is withheld that would greatly undermine the credibility of an important witness on whose testimony the decision to indict probably depended. See Commonwealth v. Connor, 392 Mass. 838, 854 (1984).
The conduct of the grand jury themselves may require setting aside an indictment. We have suggested that an indictment may *847not be allowed to stand where a defendant has made a prima facie showing of bias or prejudice on the part of the grand jury “so egregious as to result in an indictment based on ‘hatred or malice,’ within the meaning of G. L. c. 277, § 5,” and thus in violation of the oath of the grand jury. Commonwealth v. McLeod, supra at 734.
The question in this case is not whether the integrity of the grand jury was impaired by misconduct that unfairly resulted in an indictment. Rather, the question here is whether the failure to instruct the grand jury on manslaughter, for which there is no duty, nevertheless is so unfair that the integrity of the grand jury is impaired and the only remedy is to impose such a duty. It is settled that the “Commonwealth is not required to present evidence of so-called defenses or otherwise disprove such matters before the grand jury.” Commonwealth v. Silva, 455 Mass. 503, 511 (2009). Specifically, the Commonwealth is not required to inform a grand jury of the differences between murder and manslaughter or the relevance of intoxication. See Commonwealth v. Bousquet, 407 Mass. 854, 860 (1990). See also Commonwealth v. Coleman, 434 Mass. 165, 172 (2001) (prosecutor’s duty is to present evidence and explain meaning of law concerning indictment sought); Commonwealth v. Noble, supra at 48 (Commonwealth not required to inform grand jury as to lesser included offense for which it seeks indictment, unless requested); Commonwealth v. Smith, 414 Mass. 437, 441 (1993) (same); Attorney Gen. v. Pelletier, 240 Mass. 264, 310 (1922) (same). Where, as here, the evidence presented to the grand jury supports an indictment for murder in the second degree, there is nothing unfair about not informing the grand jury about the elements of manslaughter.3
The accusation of murder in the second degree has been supported by probable cause to arrest for that crime. A grand jury are not entitled simply to choose between murder and manslaughter where the Commonwealth has presented credible evidence to support an accusation of murder in the second degree. Ante at 836 (Gants, J., concurring). A petit jury, which determine guilt, normally would be instructed to return a verdict for *848the highest crime proved beyond a reasonable doubt against the defendant. See Commonwealth v. Dickerson, 372 Mass. 783, 797 (1977). The grand jury, which are merely an accusatory body that do not determine guilt, do not have greater power than a petit jury in this regard.
To the extent Justice Gants would allow a grand jury to weigh the evidence and resolve any conflict in favor of manslaughter rather than murder where there is substantial evidence of mitigation, ante at 841 n.3, this would require a presentation to the grand jury that is more like a preliminary trial in its complexity than a determination of probable cause to arrest — the decision faced by a police officer who is about to make an arrest. The issue has become not whether there was probable cause to arrest for murder, but whether an officer more precisely and after deliberation should have arrested for murder or for manslaughter. A police officer typically has neither the time nor the facts to make such a decision.
The United States Supreme Court has said:
“In dealing with probable cause, ... as the very name implies, we deal with probabilities. These are not technical; they are the factual and practical considerations of everyday life on which reasonable and prudent men, not legal technicians, act. . . . Probable cause exists where ‘the facts and circumstances within their [the officers’] knowledge and of which they had reasonably trustworthy information [are] sufficient in themselves to warrant a man of reasonable caution in the belief that’ an offense has been or is being committed. . . . These long-prevailing standards seek to safeguard citizens from rash and unreasonable interference with privacy and from unfounded charges of crime. They also seek to give fair leeway for enforcing the law in the community’s protection. Because many situations which confront officers in the course of executing their duties are more or less ambiguous, room must be allowed for some mistakes on their part. But the mistakes must be those of reasonable men, acting on facts leading sensibly to their conclusions of probability. The rule of probable cause is a practical, nontechnical conception affording the best compromise that has been found for accommodating these often opposing interests. Requiring *849more would unduly hamper law enforcement. To allow less would be to leave law-abiding citizens at the mercy of the officers’ whim or caprice.”
Brinegar v. United States, 338 U.S. 160, 175-176 (1949), quoting Carroll v. United States, 267 U.S. 132, 162 (1925). The burden this places on prosecutors and the grand jury to sort out whether the defendant should have been arrested for murder versus manslaughter is a complex exercise that needlessly squanders dwindling resources for no discemibly useful purpose. The only question for the grand jury should be whether the evidence was sufficient to support a decision to arrest for murder. Any inquiry and decision beyond that is in the nature of an adjudicatory decision and appropriately should be reserved for the petit jury. A grand jury have no greater responsibility than a police officer when acting on probable cause to arrest. The officer has no duty to investigate and deliberate over possible defenses. See Baker v. McCollan, 443 U.S. 137, 145-146 (1979).
The legal authority on which Justice Gants primarily relies, State v. Hogan, 336 NJ. Super. 319, 340-343, 344 (App. Div.), cert. denied, 167 NJ. 635 (2001), does not support his theory. Ante at 842-843. That case establishes a duty on the part of a prosecutor to instruct a grand jury as to only those defenses “that would, if believed, result in a finding of no criminal liability, i.e., a complete exoneration” (emphasis added). State v. Hogan, supra at 342. As to complete, or “exculpatory” defenses, id., the prosecutor’s duty arises “only when the facts known to the prosecutor clearly indicate or clearly establish” that the accused acted in a manner contemplated by such defense (emphasis added). Id. at 343. There is no duty to instruct the grand jury where the defense is a “mitigating” defense, that is, one that, if believed, would not result in a finding of no criminal liability, or complete exoneration. See id. at 342. Thus, the role of the grand jury to eliminate a “needless or unfounded prosecution” requires that they confine themselves only to those defenses that would result in complete exoneration, not those that merely mitigate the degree of guilt.4 See id. at 341-342. See also People v. Valles, 62 N.Y.2d 36, 38-39 (1984).
*850Massachusetts jurisprudence regards heat of passion, reasonable provocation, and sudden combat as mitigating circumstances, not complete defenses. “Voluntary manslaughter is . . . ‘an intentional killing, which is mitigated by extenuating circumstances’ ” (emphasis in original). Commonwealth v. Whitman, 430 Mass. 746, 753 (2000), quoting Commonwealth v. Squailia, 429 Mass. 101, 109 (1999). Heat of passion, reasonable provocation, and sudden combat are considered defenses, grounded in the recognition of human frailty, which palliate malice. See Commonwealth v. Webster, 5 Cush. 295, 304 (1850). Thus, there is no basis under State v. Hogan, supra, to require a prosecutor in this case to instruct the grand jury on manslaughter. As the court said in that case when discussing why it would not require prosecutors to instruct a grand jury even as to complete defenses that were not “clearly establish[ed],” “[i]t is unrealistic to call upon a prosecutor to provide the grand jury with a sophisticated analysis of the law where he does not have the benefit of the views of the defense to warn him of potential problems and pitfalls.” State v. Hogan, supra at 343-344. State v. Hogan is consistent with our jurisprudence. See Commonwealth v. Geagan, 339 Mass. 487, 499, cert. denied, 361 U.S. 895 (1959), quoting Commonwealth v. Knapp, 9 Pick. 495, 495-496 (1830).
This analysis is even more compelling as to mitigating, or incomplete defenses, such as heat of passion, reasonable provocation, and sudden combat. “By its very nature, the grand jury does not consider a full and complete adversarial presentation, ‘and the instructions are not made after consideration [and with the benefit] of the views of the defense.’ ” State v. Hogan, supra at 343, quoting State v. Schmidt, 213 N.J. Super. 576, 584 (App. Div. 1986), rev’d on other grounds, 110 N.J. 258 (1988). A requirement that the grand jury be instructed on the elements of voluntary manslaughter in this case5 is a significant departure *851from the historic and practical nature of the grand jury, it calls on the grand jury to perform more than an accusatory or investigative function, and it needlessly and unfairly burdens police and prosecutors to develop murder cases before learning about a defendant’s case through reciprocal discovery. It is more consonant with public justice to sort out these issues at a subsequent trial.
Justice Lenk would create a new rule to give grand jurors “suitable tools for their enhanced task” of “deciding] whether [a juvenile should] be treated for all purposes as an adult,” ante at 832, and which would establish the grand jury as the “sole gatekeeper between the adult and juvenile justice systems.” Ante at 824. This new rule would have the practical effect of forcing prosecutors to present precisely the type of evidence needed to disprove any defenses or mitigating circumstances that Justice Lenk acknowledges is not required under our jurisprudence. Justice Lenk’s view to the contrary, without such evidence the newly equipped grand jury will have an open invitation to reject an otherwise properly supported murder indictment. It is not even clear if the grand jury should be instructed to return an indictment for the highest crime shown, or if they have unfettered powers of charge nullification. Cf. Commonwealth v. Dickerson, 372 Mass. 783, 797 (1977) (petit juries should be instructed to return verdict of highest crime proved beyond reasonable doubt).
In advocating this gatekeeper role for the grand jury, reliance is placed in part on the procedure that existed under the statute that governed juvenile transfers prior to the enactment of the youthful offender act in 1996. As she notes, prior to 1996, transfer of a juvenile under G. L. c. 119, § 61, as amended by St. 1991, c. 488, § 3, for trial as an adult required a two-step adversary process. See Commonwealth v. Clifford C., 415 Mass. 38 (1993). The first step required a judge of the Juvenile Court to determine if there was probable cause to believe the juvenile committed the offense in question. Id. at 39-40. If the judge found probable cause, the judge then considered the issues of the juvenile’s dangerousness and amenability to rehabilitation. At this second phase of the transfer hearing a prosecutor could present evidence of the juvenile’s prior record, history of violence *852as well as evidence of nonviolent criminal conduct, aggressive tendencies, behavioral problems, and any other type of evidence relating to dangerousness and amenability to rehabilitation. Evaluations or opinions of experts also were admissible. Of course, the juvenile could contest such evidence and present his own evidence. Id. at 40-46. None of this material can be presented to the post-1996 gatekeeper grand jury, and Justice Lenk does not suggest otherwise. However, this leaves unanswered the question how the grand jury are to perform their role as gatekeeper, a judicial role that appears to be well beyond the traditional role of the grand jury as “an informing and accusing body.” Commonwealth v. Geagan, supra at 497, quoting Commonwealth v. Woodward, 157 Mass. 516, 517 (1893). See La-taille v. District Court of E. Hampden, 366 Mass. 525, 532 (1974).
A point is made that “[t]he grand jury returned the murder indictment that the Commonwealth sought without the defendant’s status as a juvenile having been factored into the process in any manner,” but no meaningful insight or guidance is offered as to how the grand jury should go about making an informed decision in this regard. Ante at 827. To complicate matters further, the questions of how judicial review of the decision of the gatekeeper grand jury may be pursued, and the standard of review, are not addressed. General Laws c. 119, § 61, once governed transfer hearings, but that statute was repealed by St. 1996, c. 200, § 7. There is nothing in its place because there was a comprehensive overhaul of the juvenile justice system, and as to murder, the Legislature determined that a direct indictment was all that was needed.
I believe there are two flaws in the rationale behind the gatekeeper grand jury. One is the statement that “the animating purpose of [three recent Supreme Court[6]] cases appears to be an effort to foreclose ‘criminal procedure laws that fail to take defendants’ youthfulness into account at all.’ ” Ante at 831, quoting Graham v. Florida, 130 S. Ct. 2011, 2031 (2010). Justice Lenk further states, “There is, however, no reason to think that the factors taken into account by the United States Supreme *853Court... are without force when considering whether it is appropriate for the grand jury to receive legal instruction before rendering a decision to indict a juvenile for murder.” Ante at 831 note 27. I disagree. The cases involved, and the factors discussed by the Supreme Court in those cases, focused exclusively on sentencing and the application of the prohibition in the Eighth Amendment to the United States Constitution against cruel and unusual punishment to certain juvenile defendants who had been charged as adults. It is axiomatic that the decision to charge someone is not punishment. Therefore, neither the Eighth Amendment prohibition against cruel and unusual punishment nor Eighth Amendment jurisprudence should apply to the return of an indictment.7
The reliance on the trilogy of Supreme Court cases is unpersuasive. In Miller v. Alabama, 132 S. Ct. 2455, 2464 (2012), the Court was careful to point out that Roper v. Simmons, 543 U.S. 551 (2005), and Graham v. Florida, supra, “establish that children are constitutionally different from adults for purposes of sentencing” (emphasis added). The Supreme Court never intimated that its reasoning in these cases could be applied in other contexts, such as the decision to charge a juvenile as an adult offender. Moreover, the Supreme Court never suggested in those cases that there was any flaw in the procedure by which the juvenile defendants had been prosecuted as adults. Indeed, in Miller, which addressed mandatory life sentences for juveniles with no possibility of parole, the Court indicated that a mandatory life sentence for juveniles was permissible on a conviction of murder. It merely held that an individualized hearing must first be afforded before the possibility of parole could be foreclosed. Miller, supra at 2471.
It is significant that there has been no mention (nor could there be) that, as a matter of constitutional law, the Supreme Court’s trilogy of Eighth Amendment cases requires prosecutors to instruct grand juries as to defenses or mitigating circumstances when seeking a murder indictment against juveniles. To be clear, today’s decision is not based on a constitutional requirement.
What I believe to be the second flaw in the rationale for the *854gatekeeper role of the grand jury begins with the degree of emphasis on the differences between the juvenile justice system and the adult criminal justice system, and certain protections that the defendant will lose by virtue of being indicted for murder. Massachusetts already provides more protections to juveniles than is constitutionally required.8 The defendant is hardly wanting for protections. If there is any concern about the loss of a particular protection, e.g., closed court rooms, then such a loss should be addressed specifically, but it is not. Indeed, an open court room is itself a valued protection. See Commonwealth v. Cohen (No. 1), 456 Mass. 94, 106 (2010).
Moreover, and of special significance, there is no possibility that the defendant will be convicted of murder in the first degree. The district attorney, acting commendably within his discretion, sought an indictment only for murder in the second degree. Although a conviction of that offense may result in a mandatory sentence of life in prison, parole is available. See G. L. c. 265, § 2. Thus, where the conviction is of murder in the second degree, there is no constitutional infirmity in such a sentence. See Miller v. Alabama, supra at 2474. Also significant is the fact that if the defendant is not convicted of murder in the second degree but of a lesser included offense, including manslaughter, the Superior Court judge would have all the sentencing options available to a judge in the Juvenile Court, including commitment to the Department of Youth Services. *855See G. L. c. 119, §§ 58, 72B. This is yet another protection available to the defendant. Justice Lenk tries to minimize this by implying that Superior Court judges lack the special expertise of Juvenile Court judges when it comes to sentencing, but the Legislature seems to think otherwise, and the assignment of responsibility for the decision is theirs to make. Ante at 828-831. Moreover, there is no basis to believe the grand jury possess any special expertise, or indeed any expertise, in juvenile matters that exceeds that of Superior Court judges.
The minimal acknowledgment of the rights the defendant actually enjoys, together with the conflation of the charging process with the sentencing process, culminates in a mantra that the defendant “will be treated as an adult for all purposes.” This appears in various forms at least three times in three consecutive paragraphs. Ante at 831-832 (Lenk, J., concurring). As indicated above, these Eighth Amendment cases suggest no such thing, nor is there even a colorable analogy to be made to the charging process. To the extent this mantra may be an expression of the view that it is impermissible to treat a juvenile as an adult for all purposes, it is not entirely a correct statement of law. A juvenile may indeed be treated as an adult for all permissible purposes for the crime of murder. No purpose has been identified in this case that is impermissible.
Finally, the statement that the prosecutor “bypassed the Juvenile Court and any attendant protections for this defendant” is not entirely fair. Ante at 832 (Lenk, J., concurring). The prosecutor acted conformably with the youthful offender act of 1996. A perception that the 1996 amendment involved here somehow deprives juveniles of certain protections should not serve as a basis to undo what the Legislature did. The Legislature was free to withdraw any protection it once offered. The Legislature’s determination that the prosecution of a juvenile accused of committing murder when he was between the ages of fourteen and seventeen years may proceed directly by indictment is a proper exercise of the legislative function. There is no claim otherwise, and there is no constitutional basis to conclude otherwise. We have recognized the broad power of the Legislature in this area. See, e.g., Charles C. v. Commonwealth, 415 Mass. 58, 69-70 (1993). The Supreme Court has acknowledged that *856Massachusetts is one of fourteen States that proceed in this manner, yet it never hinted there might be any impropriety in the chosen process. See Miller v. Alabama, 132 S. Ct. 2455, 2474 & n.15 (2012).
The Legislature is presumed to have known of the traditional role of the grand jury when it enacted the youthful offender act in 1996, yet it did not expand that role for cases in which a prosecutor seeks to indict a juvenile for murder. Instead, it streamlined the transfer process for a narrow class of crimes, namely, murder. Any rationale for expanding the role of the grand jury to act as gatekeeper in the transfer process is inconsistent with the 1996 legislation. As such, insofar as today’s decision depends in part on that expansion, it is based on an improper judicial exercise of the legislative function. In my view, the court violates the separation of powers provision of art. 30 of the Massachusetts Declaration of Rights by burdening the transfer process created by the Legislature, namely, indictment on the presentation of evidence of probable cause to arrest for murder.
Whether an indictment should be dismissed with prejudice may require a showing of such wilful deception or egregiousness that the Commonwealth should be precluded from seeking to reindict. See Commonwealth v. O’Dell, 392 Mass. 445, 447 (1984), and cases cited.
Prosecutors are not required in every instance to present to the grand jury all possible exculpatory evidence of which they are aware. See. Commonwealth v. Connor, 392 Mass. 838, 854 (1984); Commonwealth v. O’Dell, supra. See also Commonwealth v. Wilcox, 437 Mass. 33, 37 (2002).
Of course, an instruction should be given if requested by the grand jury. See Commonwealth v. Noble, 429 Mass. 44, 48 (1999), and cases cited.
In Commonwealth v. Landry, 438 Mass. 206, 211 (2002), we said that *850probable cause to arrest for a violation of G. L. c. 94C, § 27 (a), does not exist when a person presents a facially valid exchange program membership card, absent evidence that the card is invalid or the bearer is not entitled to possess it. Arguably, a grand jury would have to be so instructed when such a “complete” defense is clearly established, to avert an “unfounded prosecution.”
Justice Gants views the circumstances of this case as “rare.” Ante at 843. Voluntary manslaughter is hardly “rare,” and mitigating circumstances not unlike those presented here arise with considerable frequency.
Miller v. Alabama, 132 S. Ct. 2455 (2012). Graham v. Florida, 130 S. Ct. 2011 (2010). Roper v. Simmons, 543 U.S. 551 (2005).
It bears mention now that there are no sentencing implications of a murder indictment, only a murder conviction, a point to which I will return.
The Supreme Court has said that although the due process clause of the Fourteenth Amendment to the United States Constitution applies to Juvenile Court proceedings, that does not mean that juvenile hearings must conform with all the requirements of a criminal trial. What is required are the essentials of due process and fair treatment, which include (1) the right to adequate and timely notice of the charges, (2) the privilege against self-incrimination, (3) the right to assistance of counsel, and (4) the right to confront and cross-examine witnesses. See In re Gault, 387 U.S. 1, 33-57 (1967). Juveniles are also entitled not to be convicted except by proof beyond a reasonable doubt. See In re Winship, 397 U.S. 358, 365-367 (1970). Principles of double jeopardy also apply. See Breed v. Jones, 421 U.S. 519 (1975). Trial by jury is not constitutionally required in juvenile proceedings, see McKeiver v. Pennsylvania, 403 U.S. 528, 545-550 (1971), but it is made available in Massachusetts by statute. See G. L. c. 119, § 55A. In addition, the Massachusetts Rules of Criminal Procedure have been made applicable to juvenile proceedings in the Commonwealth. See Mass. R. Crim. P. 1 (b), as appearing in 442 Mass. 1501 (2004).