(dissenting, with whom Beck, J., joins). Prior to September 10, 1999, which was the effective date of G. L. c. 123, § 14(a), inserted by St. 1999, c. 74, § 8, the statute at issue in this case, the Legislature repealed the provisions of an earlier version of G. L. c. 123A that provided for similar commitments, albeit under a different scheme. By setting up a new statutory framework — first involving temporary detention until probable cause could be determined, then, if so determined, permitting further detention for the completion of diagnostic examinations, and then requiring that the Commonwealth petition the court for trial within fourteen days of the filing of the qualified examiners’ reports — the Legislature conditioned a petition’s progress so as to protect the important liberty interests involved. The majority views these prophylactic measures as case flow management mechanisms. I respectfully dissent.
In this case, the Commonwealth has yet to file the § 14(a) petition. The Commonwealth offers no explanation for the omission other than its interpretation of § 14(a), to which it claims compliance because of the inclusion of a request for a jury trial in its initial petition for commitment. The majority adopts the same point of view and justifies the result because the jury claim supposedly put the defendant on notice that eventually there would be a trial, citing Commonwealth v. Gagnon, 439 Mass. 826, 830-832 (2003), and Commonwealth v. Kennedy, 435 Mass. 527, 530 n.3 (2001).
Section 14(a) provides that the district attorney “may” petitian for trial of a defendant who has been temporarily committed to the Massachusetts Treatment Center for evaluation, but specifies that “[sjuch petition shall be made within 14 days of the filing of the report of the two qualified examiners” (emphasis supplied). See G. L. c. 123A, § 14(a), inserted by St. 1999, c. 74, § 8. A statute’s words are to be accorded their ordinary meaning and approved usage. Johnson v. District Attorney for the N. Dist., 342 Mass. 212, 215 (1961); Burke v. Chief of Police of Newton, 374 Mass. 450, 452 (1978). “The word ‘shall’ is ordinarily interpreted as having a mandatory or imperative obligation.” Hashimi v. Kalil, 388 Mass. 607, 609 (1983). It takes a peculiar kind of analytical casuistry to accept that the one-line jury claim contained in the initial petition satisfies the clear imperative of § 14(a).
*839I recognize that not every failure to comply with the various deadlines specified in the sexually dangerous persons commitment statute requires dismissal of the commitment petition. See Commonwealth v. Gagnon, 439 Mass. 826, 827 (2003). Instead, the Supreme Judicial Court has indicated that only failures to comply with statutory requirements that specifically affect a defendant’s liberty interest warrant dismissal of the petition. Id. at 830-831. We must, therefore, determine whether the statute’s procedure for petitioning for trial protects the defendant’s liberty interest in a way that the Commonwealth’s approach does not.1
It is instructive to begin consideration of when dismissal is required for noncompliance with the statute by examining two cases that reached opposite results based on the Commonwealth’s failures to follow time frames specified in § 13(a) of the statute.2 In the first case, Commonwealth v. Kennedy, 435 Mass. at 530, the court upheld dismissal where the Commonwealth’s qualified examiners failed to satisfy the requirement that they “shall” file reports with the court within forty-five days of the start of a defendant’s sixty-day temporary commitment. Due to repeated clerical errors, the defendant had been committed for evaluation three times, for a period “vastly in excess of” sixty days, without the examiners’ reports being filed. Ibid. Cognizant that c. 123A “provides a mechanism for a restraint on an individual’s personal liberty,” ibid., quoting from *840Hashimi v. Kalil, 388 Mass. at 610, the court ruled that the statute’s clear time requirement was “mandatory,” as are the express and nondiscretionary requirements of other statutes implicating substantive rights. Ibid., citing Hashimi v. Kalil, supra at 609-610; Commonwealth v. Cook, 426 Mass. 174, 180-181 (1997). The court therefore, upheld dismissal.
Two years later, in Commonwealth v. Gagnon, 439 Mass. at 826, the court clarified that failure to meet a deadline specified in the statute does not warrant dismissal in every case. The court indicated that the fact that c. 123A as a whole deals with physical confinement is not enough to warrant dismissal for any violation, but that a court must look at the specific statutory requirement at issue to determine whether the Commonwealth’s failure to comply actually affected a defendant’s liberty interest. Id. at 830-831.
As in Kennedy, the qualified examiners in Gagnon failed to file their reports within the forty-five days allotted by the statute. Id. at 830. In Gagnon, however, the delay for filing the reports was only eight days, and the Commonwealth filed its § 14(a) petition for trial on the same day, and thus within the sixty-day temporary commitment period. Ibid. The court concluded that dismissal was not warranted where the “failure to meet the report filing deadline did not affect the defendant’s liberty interest,” id. at 827, because, “[i]n terms of a defendant’s liberty interest, the relevant period [pursuant to § 13(a)] is the sixty-day time period,” id. at 831. The real failing in Kennedy, then, was detaining the defendant for more than sixty days without conducting the examinations and filing a petition for trial which would have moved the proceeding forward. See Commonwealth v. Kennedy, 435 Mass. at 530-531. In Gagnon, where the failure was simply not meeting the forty-five-day examination deadline, the court declared that “the party adversely affected is the Commonwealth, as it must expedite its decision to seek trial and submit its petition in order to meet that requirement prior to the expiration of the sixty-day detention.” Commonwealth v. Gagnon, 439 Mass. at 831.
Applying Gagnon to the instant case, the Commonwealth’s failure warrants dismissal only if it implicates the defendant’s liberty interest. As indicated, the Commonwealth argues that the defendant’s liberty interest was not affected because the pre*841mature request for a jury trial put him on notice to prepare a defense and allowed the case to proceed to trial (if the court scheduled it of its own accord) without delay. I disagree. The § 14(a) petitioning requirement directly affects the defendant’s liberty interest and following it properly protects the defendant’s liberty interest in ways that the Commonwealth’s approach does not.
A petition for trial under § 14(a) has serious consequences for a defendant’s liberty interest. The petition triggers the statute’s requirement that the person named in the petition shall be confined until the conclusion of the trial.3 G. L. c. 123A, § 14(a); Commonwealth v. Knapp, 441 Mass. 157, 158 (2004). Furthermore, a defendant is subject to trial and the attendant potential for indefinite civil commitment should he be found sexually dangerous. See § 14. Along with these serious consequences of a decision by the Commonwealth to proceed to trial, we see certain protections inherent in the requirement that the petition for trial only be made after the examiners file their reports.
The § 14(a) petitioning requirement creates a default position where the commitment proceeding automatically terminates at the end of the temporary commitment period unless the Commonwealth petitions for trial. This, obviously, is a real protection that directly affects a defendant’s liberty interest. The statute provides that the Commonwealth can only reverse the default termination of the proceeding after a deliberate, informed consideration, which includes a review of the qualified examiners’ reports. The petitioning requirement protects the defendant’s liberty interest by providing for the possibility that the Commonwealth will decide not to proceed against the defendant after reviewing this critical information, therefore limiting his detention to sixty days for evaluation.
*842My conclusion that consideration of the examiners’ reports is necessary before actually petitioning for trial avoids undermining the great value the statutory scheme places on the reports of the qualified examiners. As noted, the statute provides for a sixty-day deprivation of liberty “for the purpose of examination and diagnosis under the supervision of two qualified examiners.” See § 13(a), inserted by St. 1999, c. 74, § 8. This assessment and diagnosis goes to an essential element of sexual dangerousness that a defendant suffer “from a mental abnormality or personality disorder which makes the person likely to engage in sexual offenses if not confined.” G. L. c. 123A, § 1, as appearing in St. 1999, c. 74, § 6. “Whether a person suffers from a mental abnormality or personality defect, as well as the predictive behavioral question of the likelihood that a person suffering from such a condition will commit a sexual offense, are matters beyond the range of ordinary experience and require expert testimony.” Commonwealth v. Bruno, 432 Mass. 489, 511 (2000). Indeed, this court has characterized “the entire statutory scheme [as one that] creates the mechanism for gathering the facts and conducting the analysis integral to that testimony.” Commonwealth v. Dube, 59 Mass. App. Ct. 476, 482 (2003). There is something Kafkaesque, then, in the suggestion that the Commonwealth may make its decision to pursue a jury trial and indefinite commitment before examining the reports that will form a central basis of any eventual commitment.
That a well-informed decision to petition for trial, rather than a pro forma request for a jury trial, is required is further evidenced by the fact that the statute specifically allots the Commonwealth time to make the decision at this phase. As discussed supra, the statute provides for temporary commitment of a defendant for up to sixty days if probable cause is found. See § 13(a). The statute allocates up to forty-five days for the qualified examiners to conduct their reviews and file reports, ibid., then provides fourteen days for the Commonwealth to make its decision whether to petition for trial, see § 14(a). As the statute provides for detention of a defendant during this time, it is evident that it contemplates serious consideration at this point whether to advance to trial. This is more than the mere “technicality” the Commonwealth suggests in its brief, *843and it is not merely a case flow management issue as suggested by the majority, to confine a defendant for these fourteen days without requiring the Commonwealth to abide by the procedure that this period of confinement was crafted to allow.4
My view that the § 14(a) trial petitioning requirement constitutes a statutory protection of a defendant’s liberty interest also finds support in prior Massachusetts cases. The Gagnon case, 439 Mass. at 830-832, made clear that failures to comply with requirements that actually affect a defendant’s liberty interest warrant dismissal. In that case, dismissal was not warranted where the qualified examiners failed to file their reports within forty-five days because the Commonwealth had advanced the proceeding with a timely § 14(a) petition filed after consideration of the examiners’ reports. Id. at 830. In concluding that Gagnon had not suffered an infringement of his liberty interest, the court stated that in addition to not showing that he was detained for extra time, “the defendant has not suggested that . . . the delay prevented the Commonwealth from having enough time properly to evaluate the qualified examiners’ report and make an appropriate decision as to whether to file a petition for trial.” Id. at 831. This is precisely the infringement present in the instant case. The Gagnon court reiterated the importance of the Commonwealth’s adherence to the § 14(a) procedure, stating that “the party adversely affected is the Commonwealth, as it must expedite its decision to seek trial and submit its petition.” Ibid. The Commonwealth is adversely affected because making the decision whether to proceed and filing the trial petition are real tasks, not mere technicalities that it can dispose of in advance as it attempted to do in the instant case. It is only after the Commonwealth files a petition under § 14(a) *844that the court has discretion to continue a defendant’s detention pending a trial on the merits.
The Knapp case, 441 Mass. at 168-169, also indicates that the § 14(a) petitioning requirement protects a defendant’s liberty interest. The Knapp court determined that mandatory confinement pending the completion of trial is narrowly tailored to the government’s compelling interest in protecting the public because such confinement is carefully circumscribed by an array of statutory protections, including the § 14(a) requirement that the Commonwealth petition for trial only after the examiners’ reports are filed. Id. at 163-166. The court framed the due process inquiry as “whether the confinement of a convicted sexual offender alleged by the Commonwealth to be sexually dangerous, after a judge has found that probable cause exists to believe that the person is sexually dangerous, and after the Commonwealth has petitioned for trial, is narrowly tailored” (emphasis supplied). Commonwealth v. Knapp, 441 Mass. at 164. The court also specifically included the § 14(a) petitioning requirement in a list of statutory protections that render confinement pending trial narrowly tailored to the government interest, saying: “[i]n addition, the Commonwealth must have petitioned for trial after the respondent has been evaluated by at least two qualified examiners at the treatment center.” Id. at 165. My conclusion in the instant case, that the § 14(a) petitioning requirement protects a defendant’s liberty interest, is in accord with the Supreme Judicial Court’s reference to such protection as a reason the scheme satisfies due process.
The Gagnon case reflects that legitimate concern. Although I would affirm dismissal in this case because, under the approach set forth in Gagnon, the statutory requirement at issue protects a defendant’s liberty interest, I also note that this result would have the additional advantage of certainty and avoids relying on some other artifice, such as sanctions, left to the discretion of a trial judge in each case. Filing of the definitive petition with the requisite supporting qualified examiners’ reports concerning a defendant’s sexual dangerousness is not self-executing, and there is nothing in the language of § 14(a) that would deem this requirement satisfied by a jury claim contained in the initial petition.
*845For the reasons stated, I would affirm the judge’s allowance of the defendant’s motion to dismiss the Commonwealth’s petition.
Iaddition to the statutory claim that we consider here, the defendant advances a due process claim on appeal (although it is unclear whether said claim is based on the Federal Constitution or the Massachusetts Declaration of Rights). Because my analysis rests on statutory grounds alone, I have not addressed the due process argument.
In Commonwealth v. DeBella, 442 Mass. 683, 689 (2004), the Supreme Judicial Court noted that the courts need not import the constraints of § 13(a) into the interpretation of § 14(a). We heed this comment, but note that in DeBella, the court confronted the question whether the deadline to commence trial had been violated, and concluded that it had not because § 14(a) allows for extensions of the trial commencement deadline. Id. at 688-689. In so ruling, the court stated that prior statements about the strict deadlines in § 13(a) were inapplicable to § 14(a) because it contained no language of extension. Id. at 689. Likewise, the statute includes no language of exception regarding the § 14(a) petitioning requirement. Ibid. Nothing in DeBella suggests that the approach developed in Gagnon in the § 13(a) context is inapplicable in considering whether to dismiss a petition for actual failure to comply with a requirement set out in § 14(a).
The deprivation of liberty associated with the mandatory detention pending the conclusion of trial can be significant. The statute requires that trial commence within sixty days of the filing of the trial petition, unless certain limited exceptions apply. See Commonwealth v. DeBella, 442 Mass. at 687-688. However, due to the variety of allowable continuances and extensions (many of which could come at the request of, or by agreement with, the defendant) it can take significantly longer for the trial to conclude. In the instant case, for example, the defendant’s sixty-day temporary commitment period ended on October 19, 2002, approximately thirty-six months ago.
There is an additional troubling element to the majority’s position. Civil commitment pursuant to c. 123A is nonretroactive and nonpunitive partly because commitment is based on current mental condition rather than a defendant’s prior convictions for sex crimes. Commonwealth v. Bruno, 432 Mass. at 498, 501. Allowing the Commonwealth to make its ultimate decision to proceed to trial before the examiners filed their reports would suggest that the decision was based on past convictions. We would be reluctant to remove a statutory requirement created by the Legislature that adds credibility to the conclusion that civil commitment in the Commonwealth is based on present mental condition rather than past convictions.