(dissenting, with whom Ireland, J., joins). “[A]s a matter of fundamental fairness under the due process clause of the Fourteenth Amendment to the United States Constitution, a finding that an individual is no longer sexually dangerous must be as immune from subsequent or collateral attack as is a criminal judgment of acquittal.”1 Commonwealth v. Travis, 372 Mass. 238, 249 (1977) (Travis). In 1991, under the then existing provisions of G. L. c. 123A, § 9,2 a judge in the Superior Court found that the Commonwealth had “not met its *26burden of proving, beyond a reasonable doubt, that [Wayne Chapman] is a sexually dangerous person.”3 Following the 1991 proceedings, Chapman was transferred from the Massachusetts Treatment Center (treatment center) to prison, to serve the remainder of his sentence, which he completed in 2004. Approximately one month before Chapman’s scheduled release, the Commonwealth petitioned to recommit Chapman to the treatment center as a sexually dangerous person. G. L. c. 123A, § 12 (b). Because the Commonwealth’s petition and the supporting expert report impermissibly ignore the preclusive effect of the 1991 finding that Chapman was not sexually dangerous, and point to no evidence of Chapman’s conduct after the 1991 judicial determination that would, even if proved, establish probable cause to “believe that [Chapman] is a sexually dangerous person,” G. L. c. 123A, § 12 (c), I conclude that the motion judge correctly dismissed the petition. I respectfully dissent.
I do not question the court’s holding that, prior to Chapman’s release from prison in 2004, the Commonwealth could again petition to commit Chapman as a sexually dangerous person pursuant to G. L. c. 123A. The issue “whether [Chapman] is currently a sexually dangerous person, is quite different from whether he was sexually dangerous in [1991].” Commonwealth v. Bruno, 432 Mass. 489, 506 (2000) (Bruno). See Travis, supra at 249 n.5 (finding individual is not sexually dangerous at particular time “would not bar subsequent statutorily and constitutionally valid proceedings under this chapter to determine an individual’s status at the time of the subsequent proceedings”). My concern stems from the Commonwealth’s impermissible attack on the 1991 judicial determination, the Commonwealth’s substantial reliance in its petition and supporting materials on facts that may not be considered because the 1991 decision must be given preclusive effect, and on the absence of any other relevant facts in its petition concerning Chapman’s conduct since that determination in 1991.
In Bruno, supra at 504-506, this court reaffirmed that a judicial determination of a person’s sexual dangerousness must *27be given preclusive effect: Bruno did not weaken in any respect the central holding in Travis that “a finding that an individual is no longer sexually dangerous must be as immune from subsequent or collateral attack as is a criminal judgment of acquittal.” Travis, supra at 249. See Gomes v. Gaughan, 471 F.2d 794, 797 (1st Cir. 1973) (“the oppressive misuse of multiple commitment proceedings would doubtless be a violation of due process”). In Bruno, unlike here, the Commonwealth had new evidence of the defendant’s conduct following the prior proceedings sufficient to support a finding of probable cause of sexual dangerousness. Aggravated rape was the underlying conviction against Lawrence Bruno. After his release from incarceration, Bruno was arrested while on parole for, among other things, “assaulting his girl friend with whom he lived,” new conduct suggestive of sexual dangerousness. Bruno, supra at 491 n.2, 506. Thus in Bruno, we recognized that the subsequent conduct of a person not found to be sexually dangerous may be grounds for later G. L. c. 123A proceedings. See id. at 505, 506, citing Travis, supra at 249 n.5.4
As contrasted to the circumstances in Bruno, the Commonwealth in this case, in my view, has not alleged any facts of Chapman’s conduct since 1991 to meet even the low threshold of G. L. c. 123A, § 12 (6). Stripped of its revisitation of the 1991 determination,5 the Commonwealth’s allegations fall into three categories, none of which, alone or in combination, is *28“sufficient” under G. L. c. 123A, § 12 (b). First, the Commonwealth asserts that Chapman’s sexual dangerousness may be shown through “the inefficacy of the treatment that he received before 1991 and the discouraging recidivism rate of those who also received such treatment.” I agree with the court that such evidence cannot be used to prove that Chapman is now sexually dangerous, for to hold otherwise would be to permit the very attack on the earlier judicial determination that Travis and Bruno expressly forbid. Ante at 21-22.
Evidence concerning the efficacy of treatment that Chapman received before 1991 is not evidence of his conduct since 1991; it establishes only that new science suggests that the Superior Court judge who in 1991 determined that the Commonwealth had not met its burden of proving Chapman sexually dangerous, may have come to the wrong conclusion. Implicit in the Commonwealth’s theory that new scientific evidence is relevant to a determination whether Chapman is now sexually dangerous is an assumption that the Commonwealth may seek to challenge the findings of an earlier petition whenever it can proffer expert evidence that undermines an earlier judicial determination. Expert opinions and scientific scholarship concerning predictive factors of sexually dangerous recidivism are in a state of constant flux. See R.K. Hanson & K. Morton-Bourgon, Predictors of Sexual Recidivism: An Updated Meta-Analysis (2004). See also Kansas v. Hendricks, 521 U.S. 346, 360 n.3 (1997) (“psychiatric professionals are not in complete harmony in casting pedophilia, or paraphilias in general, as ‘mental illnesses’ ”). It will almost always be possible to rely on “new” science to attack an earlier determination of sexual dangerousness. Here, permitting the Commonwealth to rely on Dr. Joss’s concerns about the correctness of the 1991 determination would be contrary to our rulings in Travis and Bruno, and would provide an easy avenue for the “oppressive misuse of multiple [sexually dangerous person] commitment proceedings [that] would doubt*29less be a violation of due process.” Gomes v. Gaughan, supra at 797. See Turner v. Superior Court, 105 Cal. App. 4th 1046, 1061-1062 (2003) (holding that experts share State’s burden of showing new evidence subsequent to earlier judicial determination that defendant was not subject to commitment as sex offender). As the motion judge realized, if the Commonwealth were permitted to present expert opinion to challenge the basis of the 1991 determination, “everyday being a new day, there would be no end to the number of [pjetitions the Commonwealth could file as to a respondent’s sexual dangerousness.”
The Commonwealth also cites Chapman’s prison disciplinary record as supporting its allegation that he is a sexually dangerous person. As the court recognizes, the disciplinary record contains no such support. Ante at 24 n.16. The Commonwealth conceded that “Chapman’s disciplinary history is non-eventful.”6 “Non-even tful” prison behavior is not probative of sexual dangerousness. See Addington v. Texas, 441 U.S. 418, 426-427 (1979) (“At one time or another every person exhibits some abnormal behavior which might be perceived by some as symptomatic of a mental or emotional disorder, but which is in fact within a range of conduct that is generally acceptable. Obviously, such behavior is no basis for compelled treatment and surely none for confinement”). If Chapman’s record of prison disciplinary actions was sufficient to support a determination that there is probable cause to believe Chapman is sexually dangerous, it is hard to conceive of any circumstance in which the Commonwealth could not meet its burden. There was no showing that, in the more that thirteen years since he was determined to be not sexually dangerous, Chapman has engaged in any *30misconduct of a sexual nature.7 His prison disciplinary record is anodyne.
Third, the Commonwealth argues that Chapman’s failure to enter into sex offender treatment since 1991 is probative of sexual dangerousness. It is here — and only here — that the court agrees with the Commonwealth. In the circumstances of this case, I am not persuaded. The Commonwealth alleged that Chapman “has refused sex offender treatment” since his release from the treatment center, and for purposes of a motion to dismiss, I accept the allegation. I note, however, that the Commonwealth has made no showing that any participation was required of Chapman, or even that it was recommended to him — only that, as Dr. Joss explained, treatment “would normally be recommended” to an individual in Chapman’s position.8 Even if Chapman “refused” to participate in sex offender treatment, this cannot be probative of his present mental state. The very purpose of the 1991 determination was to free Chapman from the requirement that he be subjected to continued sex offender “treatment.”
Concluding that there is probable cause to believe Chapman is sexually dangerous because he did not undergo sexual offender treatment or therapy after he was determined not sexu*31ally dangerous in 1991 is, given the circumstances, exactly the type of “arbitrary, wrongful government action” that the due process clause bars. Foucha v. Louisiana, 504 U.S. 71, 80 (1992), quoting Zinermon v. Burch, 494 U.S. 113, 125 (1990). See Daniels v. Williams, 474 U.S. 327, 331-332 (1986); Bruno, supra at 503; Hill, petitioner, 422 Mass. 147, 154-155, cert. denied, 519 U.S. 867 (1996). The court’s holding allows the Commonwealth to initiate G. L. c. 123A proceedings against a defendant previously found not sexually dangerous not because he has engaged in conduct probative of sexual dangerousness, but because he has not voluntarily undergone some unspecified, nonmandatory treatment. The court’s holding penalizes Chapman for violating unstated and unspecified “conditions” of his release from the treatment center, where there is no reason to believe Chapman had any reason to know of the harsh consequences his “refusal” to participate in the treatment would trigger. Under the court’s holding, a prisoner released on probation from incarceration, after a determination that he is not sexually dangerous, may (if he is later incarcerated) be made subject to a new petition that he is sexually dangerous solely because of evidence that in the intervening probationary period he did not voluntarily engage in sex offender treatment, even without a showing that he had reason to know that he would be well advised to participate in such treatment, much less that his participation was a required condition of his release. In short, the court allows the Commonwealth to posit, with no notice to a defendant, post hoc, novel terms of release, and then to penalize the defendant for fading to comply with those conditions.
None of the Commonwealth’s “new” evidence is probative of Chapman’s sexual dangerousness. The motion judge correctly, in my view, concluded that the Commonwealth’s 2004 petition is based “only” on factors that were present in 1991, and correctly concluded that the Commonwealth had not met its burden required by G. L. c. 123A, § 12 (b).9
I well recognize that the 1991 judicial determination concem-*32ing Chapman’s sexual dangerousness resulted in his return to prison from the treatment center, while the same determination today would release Chapman to the public at large. We have rejected a claim of significant distinction between the former and current definitions of sexual dangerousness as provided in G. L. c. 123A. Dutil, petitioner, 437 Mass. 9, 14-15 (2002).10 Here the court could have considered that the different effect of a determination of Chapman’s lack of sexual dangerousness today, as compared to in 1991, justifies today’s decision. Cf. People v. Carmony, 99 Cal. App. 4th 317, 322-323 (2002) (California statute allowing commitment of “sexually violent predator[sj” sufficiently dissimilar from earlier statute allowing commitment of “mentally disordered sex offenders” that defendant could not invoke collateral estoppel). But, if Travis *33and Bruno are to have continued vitality, as both the Federal and State Constitutions command, I would reject the Commonwealth’s effort to relitigate the 1991 determination.
Chapman’s crimes were multiple and serious. It may be tempting to keep him incarcerated, rather than place any child at any conceivable risk if he is released. But Chapman did not receive a life sentence. He has served the full, lengthy sentence imposed on him. It may be that a longer criminal sentence was warranted in his case. “The point, however, is not how long [Chapman] and others like him should serve a criminal sentence. With his criminal record, after all, a life term may well have been the only sentence appropriate to protect society and vindicate the wrong. The concern instead is whether it is the criminal system or the civil system which should make the decision in the first place.” Kansas v. Hendricks, 521 U.S. 346, 372-373 (1997) (Kennedy, J., concurring).
The Massachusetts Constitution provides similar protection. See art. 1 of the Declaration of Rights, as amended by art. 106 of the Amendments to the Massachusetts Constitution.
In 1991, G. L. c. 123A, § 9, as amended through St. 1989, c. 555, provided that persons detained at the treatment center could “file a petition for examination and discharge once in every twelve months. . . . Unless the court finds that such person remains a sexually dangerous person, it shall order such person to be discharged from the treatment center. Discharge from the center shall not operate to terminate the sentence given concurrently with the commitment, or any other unexpired sentence.”
The Commonwealth apparently did not appeal from the decision. See Hill, petitioner, 422 Mass. 147, 155, cert. denied, 519 U.S. 867 (1996).
In Commonwealth v. Bruno, 432 Mass. 489, 504-506 (2000), we also held that the Commonwealth was not barred by res judicata or collateral estoppel from filing a G. L. c. 123A petition in the absence of an earlier judicial finding that the defendant was not sexually dangerous. In that case, the Commonwealth had sought to commit Bruno pursuant to G. L. c. 123A, but had ceased pursuing that objective before a final judicial determination. Our ruling to that effect has clear analogues in criminal law. A dismissal without prejudice for lack of evidence may enter in a criminal case after the Commonwealth has lawfully detained a suspected criminal pursuant to an indictment. Double jeopardy does not attach, of course, until the trial itself has begun. See Crist v. Bretz, 437 U.S. 28 (1978); Commonwealth v. DeFuria, 400 Mass. 485, 487 (1987) (at bench trial, jeopardy attaches when first witness sworn); Commonwealth v. Dascalakis, 246 Mass. 12, 18-19 (1923) (jeopardy attaches when jury empaneled).
The report of the Commonwealth’s expert, Dr. Joss, is replete with statements that cannot be interpreted as anything other than an attack on the 1991 determination. By way of example, one of his summary conclusions states: *28“Notwithstanding the Court’s finding in December 1991 regarding Mr. Chapman’s sexual dangerousness, I note that since that time research that has taken place on treatment effectiveness of the type of treatment Mr. Chapman was receiving and sexual recidivism of those released from the Massachusetts Treatment Center is particularly discouraging for pedophilic offenders.”
Of Chapman’s conduct since 1991, Dr. Joss’s nine-page report contains only the following: “A recent Classification Report (May, 2004) indicated that Mr. Chapman had been identified for an Alternatives to Violence and Sex Offender Treatment Programs neither of which he participated in. He did complete a Transition Plan but it is noteworthy for having expunged information related to risk situations. He has been employed in the maintenance department of the [Department of Correction]. He has had some minor and a few major disciplinary reports including one for an assault on another inmate in 1998. Additionally he used attendance at Protestant Services to transport contraband for other inmates.”
Contrary to the court’s intimation, ante at 24 n.16, Chapman’s avoidance of sexual misconduct while in prison redounds in his favor. Chapman was convicted for crimes of pedophilia, but there were certainly opportunities for sexual misconduct while Chapman was incarcerated. The former medical director of the treatment center where Chapman was committed for thirteen years has stated that rape in prison, especially of young-looking male prisoners, is alarmingly common. See Fried, Reflections on Crime and Punishment, 30 Suffolk U. L. Rev. 681, 685-687 (1997).
Due to the perverse disincentives of treatment the Commonwealth has established, many attorneys apparently routinely advise their clients not to engage voluntarily in sex offender treatment. These lawyers fear that, because their clients must waive all confidentiality rights in order to receive treatment, the frankness that such treatment requires might later be grounds for sexually dangerous person proceedings. See Bernstein, A Question of Commitment, Commonwealth (Winter 2003).
The Commonwealth’s policy in this regard is especially disturbing in light of the consensus among experts that sex offenders benefit from prompt treatment during their term of incarceration. See An Overview of Sex Offender Management, United States Department of Justice Center for Sex Offender Management 7 (2002); Detaining “Sexual Predators” in the Mental Health System, National Mental Health Association (1998).
A single justice in the Appeals Court incorrectly reasoned that the motion judge had concluded “that the Commonwealth had not made the ‘sufficient showing’ required by [G. L. c. 123A, §] 12 (e).” General Laws c. 123A, § 12 (e), allows for temporary commitment of potentially sexually dangerous persons scheduled for release from prison, “prior to” a probable cause *32determination. When the motion judge dismissed the petition, there was no probable cause determination still to come, and she could have acted (and did act) pursuant to G. L. c. 123A, § 12 {b), only. In contrast, now having concluded that the Commonwealth has in fact alleged sufficient facts and that the matter may proceed to a probable cause determination, it is entirely proper for this court to order, pursuant to G. L. c. 123A, § 12 (e), that Chapman be temporarily committed to the treatment center pending the probable cause determination.
Prior to the 1999 amendments, G. L. c. 123A, § 1, as appearing in St. 1993, c. 489, § 1, defined a “[sjexually dangerous person” in part as:
“[A]ny person whose misconduct in sexual matters indicates a general lack of power to control his sexual impulses, as evidenced by repetitive or compulsive sexual misconduct by either violence against any victim, or aggression against any victim under the age of sixteen years, and who, as a result, is likely to attack or otherwise inflict injury on such victims because of his uncontrolled or uncontrollable desires.”
Section 1, as amended through St. 2004, c. 66, §§ 1-6, now states:
“ ‘Sexually dangerous person’, any person who has been (i) convicted of or adjudicated as a delinquent juvenile or youthful offender by reason of a sexual offense and who suffers from a mental abnormality or personality disorder which makes the person likely to engage in sexual offenses if not confined to a secure facility; (ii) charged with a sexual offense and was determined to be incompetent to stand trial and who suffers from a mental abnormality or personality disorder which makes such person likely to engage in sexual offenses if not confined to a secure facility; or (iii) previously adjudicated as such by a court of the commonwealth and whose misconduct in sexual matters indicates a general lack of power to control his sexual impulses, as evidenced by repetitive or compulsive sexual misconduct by either violence against any victim, or aggression against any victim under the age of 16 years, and who, as a result, is likely to attack or otherwise inflict injury on such victims because of his uncontrolled or uncontrollable desires.”