SPINA, J.

In June, 2011, allegations of misconduct at the William A. Hinton State Laboratory Institute in Jamaica Plain (Hinton drug lab) surfaced regarding work performed by Annie Dookhan, a chemist who had been employed in the forensic drug laboratory since November, 2003. Following an internal review, the Department of Public Health launched a formal investigation of the matter in December, 2011. The investigation concluded that "Dookhan failed to follow [Hinton drug l]ab protocols for the transfer and documentation of samples for testing, and subsequently created a false record of said transfers." After being placed on paid administrative leave, Dookhan resigned from her position, effective March 9, 2012. A more extensive investigation of the Hinton drug lab was initiated in August, 2012, by the State police. As a result of this investigation, it has been alleged that, among other things, Dookhan deliberately and repeatedly falsified drug testing results, tampered with evidence, and forged signatures on documents. Although the full scope of Dookhan's purported misconduct is not yet known, it has been estimated conservatively that, during her tenure, Dookhan worked on at least 34,000 cases. The investigation of misconduct at the Hinton drug lab remains ongoing.

The three cases now before us concern the validity of certain procedures that have been adopted by the Superior Court Department of the Trial Court (Superior Court) to handle postconviction matters in criminal cases where a defendant has been convicted of a drug offense and the drugs at issue were analyzed at the Hinton drug lab. In October, 2012, the Chief Justice of the Superior Court assigned specific judges in seven counties to preside over special "drug lab sessions" that would deal with these postconviction matters. The first round of hearings focused on incarcerated defendants who had filed motions to stay the execution of their sentences in cases where the lead offense was a violation of the Controlled Substances Act, G. L. c. 94C, and Dookhan was the primary or confirmatory chemist.1 From October 15 to November 28, the judges presiding over the drug lab sessions held 589 hearings, placing an enormous burden on the Superior Court.

On November 9, 2012, this court issued an order to facilitate the expeditious handling of matters relating to the alleged misconduct at the Hinton drug lab. The order provided, in relevant part:

On November 26, 2012, in accordance with the provisions of Mass. R. Crim. P. 47, 378 Mass. 923 (1979),2 the Chief Justice of the Superior Court appointed five retired Superior Court judges as "Special Judicial Magistrate[s] of the Superior Court, to preside over criminal proceedings in connection with cases relating to the [Hinton drug lab]." These special magistrates were assigned to six counties, and the Chief Justice of the Superior Court issued to each one an "Order of Assignment" delineating his or her authority and responsibilities. It provides, in part:

As of March 6, 2013, the special magistrates had conducted more than 900 hearings, a substantial number of which pertained to defendants' motions to stay the execution of their sentences.3

The three present cases originated in Essex County. Each arose as a consequence of the implementation of the procedures established by the Chief Justice of the Superior Court for handling postconviction matters in the special drug lab sessions. Following proceedings in the Superior Court with regard to each case, which will be discussed in greater depth in subsequent portions of this opinion, the Commonwealth filed petitions in the county court pursuant to G. L. c. 211, § 3, challenging those procedures. On March 13, 2013, a single justice held a hearing on the Commonwealth's petitions. She then reserved and reported three questions to the full bench:

We shall proceed to analyze and answer each question in the context of the individual case in which it arose.5

I

Commonwealth vs. Shubar Charles

The essential facts are not disputed. On the evening of April 2, 2009, a former girl friend of Shubar Charles contacted the New Bedford police department to report that, while at her home for a birthday celebration, Charles had held a firearm to her face and threatened to kill her. The ensuing police investigation suggested that Charles could be located in Lynn. When officers from the Lynn police department converged on an apartment on North Common Street, tenants informed them that Charles had gone into a back bedroom and had been "waving around" a small handgun. Officers discovered Charles alone in the back bedroom. They searched him and found in his pants pocket twenty individual baggies of a white powdery substance that they believed to be cocaine. A further search of the bedroom uncovered, among other things, a loaded firearm. Charles was arrested and taken to the Lynn police station. During booking, he was searched again, and officers found a single bullet in the pocket of the jacket that he was wearing.

On June 5, 2009, Charles was indicted on charges of possession of a class B controlled substance (cocaine) with intent to distribute, as a subsequent offense, G. L. c. 94C, § 32A (b); possession of a firearm without a firearm identification card, G. L. c. 269, § 10 (h); unlawful possession of ammunition, G. L. c. 269, § 10 (h); and possession of a firearm after having been convicted previously of three violent crimes or three serious drug offenses, G. L. c. 269, § 10G (c) (two counts). Dookhan was the primary chemist who analyzed the substance in the baggies; she was not involved in the examination of firearm evidence. On a certificate dated December 28, 2009, Dookhan certified that the substance was cocaine.

On October 18, 2010, Charles pleaded guilty to reduced charges of possession of a class B controlled substance with intent to distribute, G. L. c. 94C, § 32A (a); unlawful possession of ammunition, G. L. c. 269, § 10 (h); and unlawful possession of ammunition after having been convicted previously of one serious drug offense, G. L. c. 269, § 10G (a). As part of the plea bargain, the Commonwealth agreed to enter a nolle prosequi on the remaining offenses. Charles was sentenced to concurrent terms of from four to seven years in the State prison for his convictions of possession of a Class B substance with intent to distribute and being a felon in possession of ammunition; he was sentenced to a concurrent term of two years in the house of correction for his conviction of unlawful possession of ammunition.6

On December 13, 2012, Charles filed a motion to stay the execution of his sentences pursuant to Mass. R. Crim. P. 31,7 as appearing in 454 Mass. 1501 (2009), which the Commonwealth opposed. He then filed a motion for a new trial pursuant to Mass. R. Crim. P. 30, as appearing in 435 Mass. 1501 (2001), raising claims pertaining to the alleged misconduct at the Hinton drug lab. In his motion for a stay, Charles asserted that his motion for a new trial likely would be successful because (1) his pleas were not knowing and voluntary where he had relied on the work of Dookhan; (2) his due process rights were violated where the Commonwealth failed "to provide true and accurate discovery prior to his guilty plea[s];" and (3) the evidence relating to Dookhan's misconduct at the Hinton drug lab constituted "newly discovered exculpatory evidence." He further asserted that, if released, he would not present a security risk.

On January 31, 2013, a special magistrate held a hearing on Charles's motion to stay the execution of his sentences. Defense counsel claimed that but for the drug indictment, Charles would not have agreed to the guilty pleas because the evidence with respect to the drug charge was the strongest. Given that Dookhan was the primary chemist on the case, defense counsel argued that there was a "great likelihood" that Charles's motion for a new trial would be successful. Further, while acknowledging that Charles had a criminal history, defense counsel asserted that Charles was "a much different person [now]," and he outlined the positive steps that Charles planned to take if released. The special magistrate allowed Charles's motion to stay execution of his sentences, subject to enumerated conditions.8 In support of his ruling, the special magistrate found that Dookhan was the primary chemist on the certificates of drug analysis, and that Charles already had served three years and nine months of his concurrent sentences, could live with family members in Lynn, and likely pleaded guilty to being a felon in possession of ammunition (one bullet) as the result of a plea deal on the drug charge.

On February 4, 2013, the Commonwealth filed an objection to the special magistrate's ruling, in accordance with the procedure set forth in the Order of Assignment.9 The Regional Administrative Justice of the Superior Court stayed the order of the special magistrate. Then, on February 8, he held a hearing on the Commonwealth's objection. The Commonwealth argued that a trial judge has no authority to stay the execution of a defendant's sentence in the absence of a pending appeal except in extraordinary circumstances, and no such circumstances were present in this case. Further, the Order of Assignment did not confer on a special magistrate the power to stay the execution of a defendant's sentence. Finally, the Commonwealth asserted that Charles's motion for a new trial was not likely to be successful, and that he would be a security risk if released. After considering Charles's motion to stay the execution of his sentences de novo,10 the judge allowed the motion, making all of the same findings as were made by the special magistrate and imposing additional conditions.11

On February 13, the Commonwealth filed with the judge a motion to stay his order, which was allowed, but only for two days. On February 14, the Commonwealth filed a petition in the county court pursuant to G. L. c. 211, § 3, seeking to extend the stay of the judge's order. In its petition, the Commonwealth challenged the authority of both the judge and the special magistrate to stay the execution of Charles's sentences prior to the disposition of his motion for a new trial, and asserted that the allowance of the motion to stay constituted an abuse of discretion. On February 15, a single justice allowed the Commonwealth's motion to extend the stay of the judge's order pending further order of the county court. On March 13, the single justice held a hearing on the Commonwealth's petition, after which she reserved and reported the three questions set forth at the beginning of this opinion.12

We turn our attention to the first of these questions, which arose from the circumstances presented in Charles's case, and consider whether a judge of the Superior Court, or a special magistrate appointed by the Chief Justice of the Superior Court pursuant to Mass. R. Crim. P. 47, has the authority to allow a defendant's motion to stay the execution of his sentence, then being served, pending disposition of the defendant's motion for a new trial. At the outset, the Commonwealth argues that a Superior Court judge does not have such authority because, pursuant to Mass. R. Crim. P. 31(a), a stay of the execution of a defendant's sentence is permissible only at the judge's discretion where an appeal is pending, and no appeal is pending in this case. See note 7, supra. Although we agree with the Commonwealth's reading of rule 31, we conclude that, in accordance with Commonwealth v. McLaughlin, 431 Mass. 506, 520 (2000) (McLaughlin), quoting Mariano v. Judge of Dist. Court of Cent. Berkshire, 243 Mass. 90, 92 (1922), a judge has the inherent power to stay sentences for "exceptional reasons permitted by law."13

It has long been recognized that the inherent powers of courts are those that are "essential to the performance of their functions, to the maintenance of their authority, and to their capacity to determine the rights of parties according to law." Blankenburg v. Commonwealth, 260 Mass. 369, 373 (1927). See Sheriff of Middlesex County v. Commissioner of Correction, 383 Mass. 631, 636 (1981). See also Crocker v. Justices of the Superior Court, 208 Mass. 162, 179 (1911) (courts have inherent power "to do whatever may be done under the general principles of jurisprudence to insure to the citizen a fair trial, whenever his life, liberty, property or character is at stake"). Significantly, "[a]lthough inherent powers may be recognized by statute, they exist independently, because they `directly affect[] the capacity of the judicial department to function' and cannot be nullified by the Legislature without violating art. 30 [of the Massachusetts Declaration of Rights]." First Justice of the Bristol Div. of the Juvenile Court Dep't v. Clerk-Magistrate of the Bristol Div. of the Juvenile Court Dep't, 438 Mass. 387, 397 (2003), quoting Opinion of the Justices, 279 Mass. 607, 613 (1932). "The very concept of inherent power `carries with it the implication that its use is for occasions not provided for by established methods.'" Commonwealth v. Boe, 456 Mass. 337, 345 n.13 (2010), quoting Brach v. Chief Justice of the Dist. Court Dep't, 386 Mass. 528, 536 (1982).

Judges must exercise their inherent authority "as necessary to secure the full and effective administration of justice." O'Coin's, Inc. v. Treasurer of the County of Worcester, 362 Mass. 507, 514 (1972). See State Realty Co. of Boston v. MacNeil Bros. Co., 358 Mass. 374, 379 (1970), quoting Link v. Wabash R.R., 370 U.S. 626, 630-631 (1962) (inherent power enables courts "to manage their own affairs so as to achieve the orderly and expeditious disposition of cases"). The boundaries of inherent judicial authority have been established on a case-by-case basis as challenges to the exercise of a particular power have arisen. See, e.g., First Justice of the Bristol Div. of the Juvenile Court Dep't v. Clerk-Magistrate of the Bristol Div. of the Juvenile Court Dep't, supra at 397-398, and cases cited. In McLaughlin, supra at 514-520, this court considered the inherent authority of a trial judge in the specific context of a stay of the execution of a defendant's sentence.

The defendant in McLaughlin was found guilty of involuntary manslaughter and arson of a dwelling house, and not guilty by reason of insanity of two charges of murder in the first degree; the judge committed him to Bridgewater State Hospital and stayed the execution of sentence on his convictions until the date of his release from civil commitment. Id. at 507, 514. On appeal, this court concluded that the judge erred in staying the execution of sentence because no exceptional reasons justified the stay, and its effect was to extend the duration of the defendant's confinement for punitive purposes. Id. at 507, 518-520. We recognized that the plain language of Mass. R. Crim. P. 31(a) "does not authorize a judge to stay execution of a penal sentence when an appeal is not pending," and we acknowledged that our jurisprudence is "largely silent on the question of the inherent power of trial judges to stay execution of sentence." Id. at 518. Although we declined to "delineate in detail the contours of trial judges' inherent power to stay execution of sentence," id. at 519-520, we said that "[t]he basic rule is clear. `Sentences are to be executed forthwith unless suspended or stayed for the exceptional reasons permitted by law'" (emphasis added). Id. at 520, quoting Mariano v. Judge of Dist. Court of Cent. Berkshire, supra. See generally Commonwealth v. Pagan, 445 Mass. 315, 322 (2005) (inherent judicial powers are invoked sparingly, but their exercise is justified by exceptional circumstances).

Here, unlike in McLaughlin, exceptional circumstances warranted the judge's exercise of his inherent power to stay the execution of Charles's sentences pending the disposition of his motion for a new trial. The magnitude of the allegations of serious and far-reaching misconduct by Dookhan at the Hinton drug lab cannot be overstated. The alleged misconduct may have compromised thousands of cases. Dookhan's role as the primary chemist in Charles's case raises significant questions regarding the veracity of the drug analysis, which purportedly served as the basis for his guilty pleas, and may be dispositive of his motion for a new trial.14 Given the ongoing investigation of misconduct at the Hinton drug lab and the uncertainty about when such investigation will be completed, the interest of justice is not served by the continued imprisonment of a defendant who may be entitled to a new trial. Cf. Lavallee v. Justices in the Hampden Superior Court, 442 Mass. 228, 246 (2004) (burden of "systemic lapse" in administration of justice "is not to be borne by defendants"). To the extent that Charles satisfies the necessary criteria for a stay of the execution of his sentences, a matter that will be discussed shortly, the allowance of a stay is properly within the judge's inherent authority.

With regard to special magistrates, the Commonwealth argues that they have no authority to allow a defendant's motion to stay the execution of his sentence, then being served, pending disposition of the defendant's motion for a new trial. We agree that special magistrates have no such authority, but we conclude that they are empowered to make proposed findings of fact and conclusions of law on a motion to stay the execution of sentence. Those findings and conclusions, in turn, shall be reviewed by a judge, who will make the ultimate decision whether to allow or deny the motion to stay.

Rule 47 of the Massachusetts Rules of Criminal Procedure permits the appointment of special magistrates to preside over certain criminal proceedings in the Superior Court. These special magistrates occupy a separate and distinct position from clerks of courts who are designated as magistrates pursuant to G. L. c. 221, § 62B. See Reporters' Notes to Rule 47, Mass. Ann. Laws Court Rules, Rules of Criminal Procedure, at 1759 (LexisNexis 2012-2013). The powers of special magistrates are delineated in rule 47. They have the authority "to preside at arraignments, to set bail, to assign counsel, to supervise pretrial conferences, to mark up pretrial motions for hearing, to make findings and report those findings and other issues to the presiding justice or Administrative Justice, and to perform such other duties as may be authorized by order of the Superior Court." Mass. R. Crim. P. 47. The responsibilities of a special magistrate are "quasi-judicial" in nature. See Reporters' Notes to Rule 47, supra. Given their position and limited powers, special magistrates do not have inherent judicial authority akin to that which can be exercised by Superior Court judges.

Pursuant to each Order of Assignment issued by the Chief Justice of the Superior Court in accordance with rule 47, the five special magistrates were appointed "to preside over criminal proceedings in connection with cases relating to the [Hinton drug lab]." In addition to the powers conferred on them by rule 47, the special magistrates also were authorized "to conduct hearings on post conviction motions, to issue orders regarding discovery, and other matters, and to make proposed findings and rulings to the Regional Administrative Justice." The special magistrates, in the first instance, serve a critically important role in addressing the extraordinary demands placed on the Superior Court by the Hinton drug lab cases. However, the Order of Assignment, when read in conjunction with rule 47, does not permit a special magistrate to stay the execution of a defendant's sentence.

Although somewhat more circumscribed, the role of a special magistrate appointed pursuant to Mass. R. Crim. P. 47 is similar in many respects to that of a master appointed pursuant to Mass. R. Civ. P. 53, as amended, 423 Mass. 1408 (1996). A master is "appointed by the court to hear evidence in connection with any action and report facts." Mass. R. Civ. P. 53(a)(i), as amended, 386 Mass. 1237 (1982). With regard to a matter not tried before a jury, "the court shall accept the master's subsidiary findings of fact unless they are clearly erroneous, mutually inconsistent, unwarranted by the evidence before the master as a matter of law or are otherwise tainted by error of law." Mass. R. Civ. P. 53(h)(1), as amended, 386 Mass. 1237 (1982). See Berish v. Bornstein, 437 Mass. 252, 268 (2002). See also Pollock v. Marshall, 391 Mass. 543, 554 & n.9 (1984). A court is to review the ultimate findings of fact by a master in light of the independent inferences that the court can draw from the subsidiary findings. See id. at 555. See also Bishay v. Foreign Motors Inc., 416 Mass. 1, 12 (1993), quoting Mass. R. Civ. P. 53(h)(1) ("The court may draw its own inferences from the master's subsidiary findings"). "To the extent that the master's ultimate findings are conclusions of law, they are subject to independent judicial review." Pollock v. Marshall, supra, citing Lucey v. Hero Int'l Corp., 361 Mass. 569, 571 (1972). In our view, this scope of review is the appropriate one to be applied to the proposed findings and conclusions of a special magistrate who has heard a defendant's motion to stay the execution of his sentence. The judge then shall enter an order allowing or denying the stay.15

Whether considered by a special magistrate or a Superior Court judge, the factors that shall be evaluated in deciding whether to allow a defendant's motion for a stay of the execution of his sentence pending the disposition of a new trial motion are the same as those relating to a stay of execution of sentence pending appeal. The first factor is whether the defendant's motion for a new trial presents an issue that "offers some reasonable possibility of a successful decision." Commonwealth v. Allen, 378 Mass. 489, 498 (1979), quoting Commonwealth v. Levin, 7 Mass.App.Ct. 501, 504 (1979). See Commonwealth v. Hodge (No. 1), 380 Mass. 851, 855 (1980). The second factor is whether the defendant's release poses a security risk. See id. Significant considerations include the defendant's "familial status, roots in the community, employment, prior criminal record, and general attitude and demeanor." Id. See Commonwealth v. Levin, supra at 505. These considerations, in turn, will inform the calculus regarding the possibility of the defendant's flight to avoid punishment, the potential danger posed by the defendant to any person or to the community, and the likelihood that the defendant will commit additional criminal acts while awaiting a decision on his new trial motion. See Polk v. Commonwealth, 461 Mass. 251, 253 (2012), citing Commonwealth v. Hodge (No. 1), supra.

In the context of a pending appeal, the practice of granting a stay of execution of sentence "is grounded in rudimentary notions of justice" because a "conviction may be reversible, but the time spent in prison is not." Commonwealth v. Levin, supra at 512-513. See Commonwealth v. Hodge (No. 1), supra at 855-856. This rationale is no less important here, notwithstanding the fact that there is no pending appeal. The allegations of misconduct at the Hinton drug lab have given rise to serious concerns about defendants who may be incarcerated as a consequence of tainted convictions. Thus, a defendant's motion to stay the execution of his sentence should be decided in an expeditious manner.16

In this case, we conclude that the judge did not abuse his discretion in allowing Charles's motion to stay the execution of his sentences. See Commonwealth v. Cohen (No. 2), 456 Mass. 128, 132-133 (2010) (describing standard of review). First, it is not disputed that Dookhan was the primary chemist who analyzed the drugs that served as the basis for Charles's conviction of possession of cocaine with intent to distribute. The ongoing investigation of the Hinton drug lab purportedly has revealed that, among other alleged misconduct, Dookhan prepared false drug reports without doing any testing and intentionally contaminated drug samples to achieve desired results. To the extent that Charles's guilty pleas were based, in whole or in part, on drug analyses performed by Dookhan, his motion for a new trial has presented an issue that "offers some reasonable possibility of a successful decision." Commonwealth v. Allen, supra, quoting Commonwealth v. Levin, supra at 504. We caution that we are engaged in an interlocutory review focused only on a stay of execution of sentence. We offer no opinion on the ultimate merits of Charles's motion for a new trial, but simply determine that he has presented a colorable claim.

Second, defense counsel described to the judge how, notwithstanding Charles's criminal history, he had matured while incarcerated, having participated in various programs that were offered at the State prison, and he did not pose a security risk. Defense counsel informed the judge that, if released, Charles would live with his brother, and he would pursue two available employment opportunities as well as further education. The judge evaluated the possible security risk posed by Charles and addressed any uncertainties by imposing conditions that effectively would confine Charles to his home for the duration of his release. It is contrary to the interests of justice that Charles remain incarcerated while the nature and scope of the alleged misconduct at the Hinton drug lab are investigated and fully ascertained.

We answer the first reported question as follows: In exceptional circumstances, a judge of the Superior Court does have the authority to allow a defendant's motion to stay the execution of his sentence, then being served, pending disposition of the defendant's motion for a new trial, but a special magistrate appointed by the Chief Justice of the Superior Court pursuant to Mass. R. Crim. P. 47 does not have such authority.17

II

Commonwealth vs. Hector Milette

The essential facts are not disputed. On December 16, 2009, Hector Milette was indicted on charges of trafficking in one hundred grams or more of cocaine, G. L. c. 94C, § 32E (b) (3) (three counts); and trafficking in fourteen grams or more of cocaine, G. L. c. 94C, § 32E (b) (1). The charges arose from Milette's role as a middleman in the sale of purported drugs to a confidential informant on three separate dates in August, 2009, and from the seizure of a plastic bag containing a white substance found during a search of Milette's residence in Haverhill on October 20, 2009. Dookhan was the primary chemist who analyzed the substances from the three August sales. On two certificates dated November 12, 2009, and on a third certificate dated December 7, 2009, she certified that the substances were cocaine. Dookhan was not involved in the analysis of the substance discovered during the execution of a search warrant at Milette's home. That sample was examined separately by another chemist at the Hinton drug lab, who certified that it was cocaine.

On May 9, 2011, Milette pleaded guilty to trafficking in twenty-eight grams or more of cocaine, G. L. c. 94C, § 32E (c) (2) (three counts); and possession of a class B controlled substance with intent to distribute, G. L. c. 94C, § 32A (a). Milette was sentenced to concurrent terms of from five years to five years and one day in the State prison for each of his three drug trafficking convictions; he was sentenced to a consecutive probationary term of three years for his conviction of possession of a class B substance with intent to distribute.18

On October 22, 2012, Milette filed a motion to stay the execution of his sentences pursuant to Mass. R. Crim. P. 31, which the Commonwealth opposed. He also filed a motion for a new trial pursuant to Mass. R. Crim. P. 30, raising claims pertaining to the alleged misconduct at the Hinton drug lab. In his motion for a stay, Milette asserted that his new trial motion likely would be successful because (1) Dookhan had signed three of the four certificates of drug analysis that served as the bases for his indictments; and (2) it was reasonably possible that the charges against him would be dismissed because Dookhan's misconduct had tainted the evidence in numerous cases that she had handled. Milette further asserted that he already had served nearly thirty-seven months of a sixty-month sentence, and that, if released, he would not present a security risk. In its opposition, the Commonwealth challenged, among other things, the authority of a trial judge to stay the execution of a defendant's sentence prior to the disposition of his motion for a new trial.

On November 13, a judge of the Superior Court held a hearing on Milette's motion to stay the execution of his sentences. Defense counsel argued that Milette had pleaded guilty to the drug charges "primarily because of the drug certifications," that he had put "great faith" in the analyses, and that now there were numerous questions concerning Dookhan's veracity and her actions during the testing procedures.19 The judge denied Milette's motion to stay on the ground that the cocaine in Milette's possession had originated from a supplier whose drugs had been analyzed by a chemist unrelated to Dookhan and the Hinton drug lab.

On February 6, 2013, Milette filed a motion for reconsideration pursuant to Mass. R. Crim. P. 13(a)(5), as appearing in 442 Mass. 1516 (2004), which was heard by a special magistrate on February 12.20 Defense counsel asserted that, since the judge's ruling on November 13, the ongoing investigation of misconduct at the Hinton drug lab had revealed "criminal involvement" so "widespread" that Dookhan had been indicted in six counties on a variety of charges. Because of such misconduct, defense counsel continued, the interests of justice required a stay of the execution of Milette's sentences. Over the Commonwealth's objection, the special magistrate allowed Milette's motion for reconsideration and then stayed the execution of his sentences. The special magistrate found that Milette already had served two-thirds of his sentences, he had presented no disciplinary problems while incarcerated, he had secured a place to live if released, Dookhan had been the primary chemist on three of the four certificates of drug analysis, and Milette's role in the drug transactions had been that of a middleman. The special magistrate set bail at $2,000 cash, which Milette posted that day, and he imposed numerous conditions on Milette's release.21 The special magistrate also declined to stay his order.

On February 13, the Commonwealth filed an objection to the special magistrate's ruling, in accordance with the procedure set forth in the Order of Assignment. That same day, the Regional Administrative Justice of the Superior Court modified Milette's conditions of release to include home confinement, except for emergency medical care and court appearances.

On February 27, the Regional Administrative Justice held a hearing on the Commonwealth's objection. The Commonwealth argued that the special magistrate had erred in allowing Milette's motion for reconsideration because no significant change in circumstances had occurred since a judge denied Milette's motion to stay the execution of his sentences on November 13. Further, the special magistrate, who no longer was an active Associate Justice of the Superior Court, did not have the authority to reconsider a judge's ruling and order a stay, and, in any event, a stay of the execution of a defendant's sentence could not be entered where there was no pending appeal. Finally, the Commonwealth asserted that, even if the special magistrate did possess the requisite authority, Milette had failed to show that his motion for a new trial likely would be successful, and that he would not be a security risk if released.

In a written memorandum of decision, the second judge vacated the stay of execution of sentences entered by the special magistrate on February 12, and he ordered Milette back into custody to resume serving the remainder of his State prison sentences. The judge concluded that both he and the special magistrate had the authority to issue a stay of execution and to set conditions of release. Moreover, recognizing the extensive evidence that had come to light regarding Dookhan's malfeasance at the Hinton drug lab, the judge stated that such a change in circumstances since November 13 warranted reconsideration of a judge's initial denial of Milette's motion for a stay of the execution of his sentences. However, in light of the proceedings in Commonwealth vs. Charles, No. SJ-2013-0066, and the perceived absence of any meaningful difference between that case and this one, the judge declined to uphold the order of the special magistrate allowing Milette's motion for reconsideration and granting the stay.

Meanwhile, on February 21, the Commonwealth had filed a petition in the county court pursuant to G. L. c. 211, § 3, seeking to stay the order of the special magistrate.22 In its petition, the Commonwealth requested clarification of the authority of both a judge and a special magistrate to stay the execution of a defendant's sentence pending the disposition of his motion for a new trial, and challenged the authority of a special magistrate to reconsider a judge's ruling on such a motion to stay. On March 13, the single justice held a hearing on the Commonwealth's petition, after which she reserved and reported the three questions set forth at the beginning of this opinion.23

We turn our attention to the second of these questions, which arose from the circumstances presented in Milette's case, and examine whether a special magistrate has the authority to reconsider and allow a motion to stay the execution of a defendant's sentence where a judge of the Superior Court previously had denied the same motion.24 The Commonwealth contends that a special magistrate has no such authority. We agree.

As a general matter, Massachusetts courts have recognized that "it is within the inherent authority of a trial judge to `reconsider decisions made on the road to final judgment.'" Herbert A. Sullivan, Inc. v. Utica Mut. Ins. Co., 439 Mass. 387, 401 (2003), quoting Franchi v. Stella, 42 Mass.App.Ct. 251, 258 (1997). See Commonwealth v. Cronk, 396 Mass. 194, 196 (1985) ("While the Massachusetts Rules of Criminal Procedure do not expressly permit a judge to rehear a matter, no policy prohibits reconsideration of an order or judgment in appropriate circumstances"). Although a judge is not obligated "to reconsider a case, an issue, or a question of fact or law, once decided, the power to do so remains in the court until final judgment or decree." Peterson v. Hopson, 306 Mass. 597, 601-602 (1940), and cases cited. See Commonwealth v. Gross, 447 Mass. 691, 693 n.2 (2006), quoting King v. Globe Newspaper Co., 400 Mass. 705, 707 (1987), cert. denied, 485 U.S. 940 and 485 U.S. 962 (1988). The party filing a motion for reconsideration "should specify (1) `changed circumstances' such as (a) newly discovered evidence or information, or (b) a development of relevant law; or (2) a particular and demonstrable error in the original ruling or decision." Audubon Hill S. Condominium Ass'n v. Community Ass'n Underwriters of Am., Inc., 82 Mass.App.Ct. 461, 470 (2012). See Barbosa v. Hopper Feeds, Inc., 404 Mass. 610, 622 (1989); Peterson v. Hopson, supra at 599-600, and cases cited. Whether to allow the motion is left to the judge's discretion. See Audubon Hill S. Condominium Ass'n v. Community Ass'n Underwriters of Am., Inc., supra. "A judge should hesitate to undo his own work.... Still more should he hesitate to undo the work of another judge.... But until final judgment ... there is no lack of power, and occasionally the power may properly be exercised." King v. Globe Newspaper Co., supra, quoting Peterson v. Hopson, supra at 603 (citations omitted).

As we discussed in Part I, supra, neither the position nor the authority of a special magistrate is coextensive with that of a trial judge. The Order of Assignment, when read in conjunction with Mass. R. Crim. P. 47, does not permit a special magistrate to reconsider a judge's decision on a defendant's motion to stay the execution of his sentence. We recognize that, once a judge has ruled on such a motion, a change in circumstances may arise that would warrant a reevaluation of the original decision. Where modification of the original decision is in order, the judge shall determine the procedure to be followed and make the necessary ruling. In those instances when the judge's decision would benefit from an evidentiary hearing on the changed circumstances, a special magistrate is empowered to make proposed findings of fact and conclusions of law on the motion for reconsideration. Those findings and conclusions, in turn, shall be reviewed by a judge, who will make the ultimate determinations whether to allow or deny the motion for reconsideration and, then, whether to modify the original decision.

Here, we need not consider further the underlying merits of the judge's decision on Milette's motion for reconsideration. Shortly after oral argument before this court, Milette's motion for a new trial was allowed, he pleaded guilty to various drug offenses, and he was sentenced on those convictions. See note 23, supra. The issue of Milette's motion for reconsideration now is moot because he no longer has a personal stake in its outcome. See Commonwealth v. Dotson, 462 Mass. 96, 98-99 (2012) (describing mootness doctrine).

We answer the second reported question, "No."

III

District Attorney for the Eastern District vs. Superior Court Department of the Trial Court

The essential facts are not disputed. Following the commencement of the special drug lab sessions, procedures were put in place in the Superior Court for the taking of guilty pleas after the allowance of a defendant's motion for a new trial. Pursuant to Mass. R. Crim. P. 47 and the Order of Assignment, special magistrates were authorized, in appropriate circumstances, to conduct guilty plea colloquies with defendants. Standardized written forms were prepared for use by the special magistrates in the taking of a defendant's guilty plea.25

In accordance with the Superior Court procedures, a defendant would appear before a special magistrate asking to change his plea to guilty of the charges against him. The special magistrate would inform the defendant that he had a right to appear before a Superior Court judge, who would conduct a plea colloquy by asking questions about the voluntariness of the defendant's decision and his understanding of the consequences of his guilty plea. The special magistrate also would inform the defendant that, as a special magistrate, he could conduct the plea colloquy, make findings regarding the defendant's decision to plead guilty, and report those findings to a judge, who then would conduct further proceedings in the case, including accepting or rejecting the proffered plea, and, if accepted, would impose sentence. At this juncture, the special magistrate would continue with a plea colloquy only with the defendant's written consent.26 In giving his consent, the defendant also would acknowledge that he was satisfied that his attorney had provided representation in an effective and competent manner.

If the defendant consented to proceeding before a special magistrate, the special magistrate would conduct an oral colloquy to determine whether the defendant was entering his guilty plea voluntarily and with a full understanding of its consequences.27 The special magistrate then would make specific findings, including whether (1) the defendant was under the influence of drugs or alcohol; (2) the defendant had reported that he was suffering from any mental impairment that would affect his ability to understand and participate in the proceedings; (3) the defendant's decision to plead guilty was the result of any threat, force, coercion, or promise, or was solely because he was guilty; (4) the defendant's decision to plead guilty was made after consultation with competent counsel; (5) the defendant was aware of the potential consequences of pleading guilty, including the obligation to provide a deoxyribonucleic acid sample to the State; (6) the defendant had been informed of the maximum penalties for each of the indictments to which he was pleading guilty; (7) there was a factual basis for the defendant's plea in the evidence presented by the Commonwealth; (8) the defendant fully understood that, if he was not a citizen of the United States, his conviction would have immigration consequences; (9) the defendant had knowingly, intelligently, and voluntarily waived all of his statutory and constitutional rights, as explained during the colloquy, and understood the consequences of his guilty plea; and (10) the defendant understood that there was an ongoing investigation at the Hinton drug lab, and that he was waiving all claims relating to alleged irregularities there. Finally, the special magistrate would report these findings to a Superior Court judge for further proceedings, and would recommend that the judge accept the defendant's guilty plea and the proposed sentence agreed to by the prosecutor and defense counsel during the colloquy. The defendant then would appear before the judge, who would review the findings and recommendation of the special magistrate, ask any relevant additional questions, accept the plea, and impose sentence.

The district attorney for the Eastern District (district attorney) has refused to participate in guilty plea proceedings before a special magistrate, insisting that such proceedings take place before a judge in order to assure the validity of the plea. Consequently, all of the plea proceedings in the special drug lab sessions held in Essex County have been conducted in this manner. However, special magistrates have conducted guilty plea colloquies in other counties.

On March 1, 2013, the district attorney filed a petition in the county court pursuant to G. L. c. 211, § 3, which the Superior Court opposed. The district attorney sought clarification of the validity of guilty plea proceedings conducted by special magistrates pursuant to the Order of Assignment. On March 13, the single justice held a hearing on the petition, after which she reserved and reported the three questions set forth at the beginning of this opinion.

We turn our attention to the third of these questions and consider (1) whether it is appropriate for this court to answer the question set forth in part (b) regarding the validity of plea colloquies conducted by special magistrates, where, under the terms of the protocol established by the Superior Court, neither side can be required to submit over its objection to a plea colloquy conducted by a special magistrate, and where, to date, all of the colloquies in Essex County have been conducted by judges and not by special magistrates; and (2) whether a special magistrate has the authority under Mass. R. Crim. P. 47 to conduct a guilty plea colloquy and report findings concerning such issues as the voluntariness of the proposed plea and the factual basis for the plea to a Superior Court judge. As to the first part of this question, the Superior Court asserts that where there have been no plea colloquies conducted by special magistrates in Essex County, there is no "actual controversy" for this court to resolve. Therefore, it follows that the issue presented in the second part of the question is not justiciable. We disagree.

General Laws c. 211, § 3, provides that "[t]he supreme judicial court shall have general superintendence of all courts of inferior jurisdiction to correct and prevent errors and abuses therein if no other remedy is expressly provided...." This court's superintendence powers are discretionary and will be exercised only in "the most exceptional circumstances." Costarelli v. Commonwealth, 374 Mass. 677, 679 (1978). See Planned Parenthood League of Mass., Inc. v. Operation Rescue, 406 Mass. 701, 706 (1990). Generally speaking, a party seeking review under G. L. c. 211, § 3, must demonstrate both a violation of the party's substantive rights and the unavailability of adequate relief through the ordinary appellate process. See id., quoting Dunbrack v. Commonwealth, 398 Mass. 502, 504 (1986). However, we have said that where "a systemic issue affecting the proper administration of the judiciary has been presented, resolution of the issue by this court is appropriate." Simmons v. Clerk-Magistrate of the Boston Div. of the Hous. Court Dep't, 448 Mass. 57, 61 (2006). See Messing, Rudavsky & Weliky, P.C. v. President & Fellows of Harvard College, 436 Mass. 347, 351 (2002). See also A Juvenile v. Commonwealth (No. 1), 380 Mass. 552, 555-556 (1980) (resolving question of proper transfer practice between Boston Juvenile Court and Superior Court). In the past, we have exercised our general superintendence powers to resolve, among other things, "important issues with implications for the effective administration of justice" and "matter[s] of public interest that may cause further uncertainty within the courts." First Justice of the Bristol Div. of the Juvenile Court Dep't v. Clerk-Magistrate of the Bristol Div. of the Juvenile Court Dep't, 438 Mass. 387, 391 (2003) (resolving internal dispute between members of judicial department). See Bradford v. Knights, 427 Mass. 748, 750-751 (1998) (determining that judges of Boston Municipal Court Department have inherent authority to rehear denials of applications for criminal complaints by clerks of that court).

It is undisputed that the allegations of serious and far-reaching misconduct by Dookhan at the Hinton drug lab have raised significant concerns about the administration of justice in criminal cases where a defendant has been convicted of a drug offense and the drugs at issue were analyzed at that facility. Although the full scope of the misconduct is not yet known, thousands of cases may have been compromised. In response to this burgeoning crisis, the Superior Court took action by developing and implementing procedures, across several counties, to review and resolve affected cases, including allowing special magistrates to conduct guilty plea colloquies. The allegations of misconduct at the Hinton drug lab, and the implications of such misconduct on defendants who have been convicted of drug offenses, present exceptional circumstances warranting this court's exercise of its superintendence powers. It is incumbent on us, at the early stages of this unfolding situation, to address uncertainties regarding the propriety of the procedures that have been implemented by the Superior Court. Notwithstanding the fact that special magistrates have not conducted guilty plea colloquies in Essex County, they have conducted such colloquies in other counties. We conclude that the legality of these proceedings presents a systemic concern that this court should resolve now through the exercise of its general superintendence powers under G. L. c. 211, § 3.

With regard to the second part of the third reported question, the district attorney contends that the procedure enabling special magistrates to conduct guilty plea colloquies in special drug lab sessions calls on special magistrates to act beyond the scope of their authority. Thus, in the district attorney's view, the validity of these guilty pleas has been rendered uncertain. We disagree and conclude that the procedure passes legal muster.

As we have discussed at some length, the Order of Assignment, in conjunction with Mass. R. Crim. P. 47, authorizes a special magistrate "to make proposed findings and rulings to the Regional Administrative Justice." Significantly, the special magistrate is neither accepting a defendant's guilty plea nor imposing a sentence. That is the ultimate function of the judge. See Whitney v. Commonwealth, 337 Mass. 722, 723 (1958) (sentence is judgment in criminal case). In the extraordinary circumstances presented here, the role of the special magistrate is to expedite the processing of an anticipated avalanche of cases through the special drug lab sessions by, preliminarily, making findings whether, among other things, a defendant has decided to plead guilty to the charges against him voluntarily and with a full understanding of the consequences of such action. See Commonwealth v. Lopez, 447 Mass. 625, 628 (2006), citing Commonwealth v. Fernandes, 390 Mass. 714, 715-718 (1984) ("To be effective, a guilty plea must be knowingly and voluntarily tendered directly from the defendant"). After doing so, the special magistrate simply reports his or her findings to a judge. The standardized written forms used in the Superior Court have been designed to assist the special magistrate in fulfilling his fact-finding responsibilities, to protect the defendant's constitutional and statutory rights, and to guarantee the proper administration of justice. Moreover, it is noteworthy that the individuals appointed to serve as special magistrates are retired Superior Court judges who are well acquainted with the content, scope, and importance of guilty plea colloquies, and are able to engage in "a real probe of the defendant's mind." Commonwealth v. Foster, 368 Mass. 100, 107 (1975). See Commonwealth v. Sherman, 451 Mass. 332, 338 (2008); Commonwealth v. Fernandes, supra.

"[W]hat is wanted from [a guilty plea] colloquy is the basic assurances that the defendant, represented by counsel, with whom he has consulted, is free of coercion or the like, understands the nature of the crime charged, knows the extent of his guilt, recognizes the basic penal consequences involved, and is aware that he can have a trial if he wants one" (footnotes omitted). Commonwealth v. Nolan, 19 Mass.App.Ct. 491, 498-499 (1985). The protocol implemented by the Superior Court provides these necessary assurances. Once a judge receives the special magistrate's findings, the judge shall hold a hearing with the defendant and his counsel, adopt or revise the findings, accept or reject the plea, and, if the judge accepts the plea, impose sentence. In so doing, the judge shall engage the defendant and verify that the responses the defendant gave during the plea colloquy with the special magistrate remain accurate and true. The judge must be satisfied that the defendant's guilty plea was made intelligently and voluntarily, thereby confirming that the plea is a proper reflection of the defendant's guilt and a fair termination of the criminal proceedings against him.

We answer both parts of the third reported question, "Yes."

IV

These matters are remanded to the single justice for further proceedings, consistent with this opinion, as appropriate.

So ordered.