Five petitions for writs of habeas corpus have been consolidated since each presents substantially the same question.1 Each petitioner is presently incarcerated in a Washington state mental hospital, committed as criminally insane after an acquittal of criminal charges by reason of insanity.. They now challenge the criminal mental commitment law as violative of equal protection and due process. .
*416Essentially petitioners argue that the present statutory scheme2 applies a single standard (that of present dangerousness) to two indistinguishable groups — those acquitted of criminal charges on grounds of insanity, and everyone else subject to mental commitment. This single standard, they argue, is the subject of an unjustifiable difference in burden of proof and procedure: the insanity-acquitted individual carries the procedural burden, while in civil commitment proceedings the burden is entirely the State’s.
The civil commitment statute, RCW 71.05, provides for progressively more lengthy detention of individuals based on a judicial determination of mental incapacity which must be progressively more severe for the longer detention period and which requires a progressively greater burden of proof from the State. In order to commit an individual for 14 days, the State must show by a preponderance of the evidence that the individual is a mentally ill person whose mental disorder presents a likelihood of serious harm to the individual himself or to others, or who is gravely disabled. RCW 71.05.240. In order to continue detention beyond the 14 days, the State must show by clear, cogent, and convincing evidence that:
(1) Such person has threatened, attempted, pr inflicted physical harm upon the person of another or himself after having been taken into custody for evaluation and treatment, and, as a result of mental disorder presents a likelihood of serious harm to others or himself; or
(2) Such person was taken into custody as a result of conduct in which he attempted or inflicted physical harm upon the person of another or himself, and continues to present, as a result of mental disorder, a likelihood of serious harm to others or himself; or
(3) Such person is in custody because he has committed acts constituting a felony, and as a result of a mental disorder, presents a substantial likelihood of repeating similar acts. In any proceeding pursuant to this subsec*417tion it shall not be necessary to show intent, wilfulness, or state of mind as an element of the felony; or
(4) Such person is gravely disabled.
RCW 71.05.280, as amended by Laws of 1974, 1st Ex. Sess., ch. 145, § 19, p. 491.
We equated clear, cogent, and convincing evidence to the criminal standard of beyond a reasonable doubt in In re Levias, 83 Wn.2d 253, 517 P.2d 588 (1973). Upon such a showing, a 90-day commitment order issues.
Commitment after the 90-day period requires the State to show by a new petition for treatment that the committed person:
(a) Has threatened, attempted, or inflicted physical harm upon the person of another during the current period of court ordered treatment and, as a result of mental disorder presents a likelihood of serious harm to others; or
(b) Was taken into custody as a result of conduct in which he attempted or inflicted serious physical harm upon the person of another, and continues to present, as a result of mental disorder, a likelihood of serious harm to others; or
(c) Is in custody pursuant to RCW 71.05.290(3) and as a result of mental disorder presents a substantial likelihood of repeating similar acts; or
(d) Continues to be gravely disabled.
RCW 71.05.320(2), as amended by Laws of 1974, 1st Ex. Sess., ch. 145, § 23, p. 494.3
A commitment period of 180 days is then authorized. No single commitment period can exceed 180 days. Successive commitments of 180 days are permissible on subsequent *418showings of the same elements by the State in subsequent hearings.
It will be noted that the commission of acts constituting a felony is a ground for commitment for 90 days under RCW 71.05.280(3). However, that ground as such is only indirectly carried into the statute which authorizes commitment for 180 days. This would appear to be the result of a drafting error; RCW 71.05.320(2) (c) refers to RCW 71.05.290(3), which relates to persons incompetent to stand trial. Presumably, the section should instead refer to RCW 71.05.280(3), which relates to the commission of acts constituting a felony. Such an interpretation is consistent with the language of RCW 71.05.320(2) (c) (“substantial likelihood of repeating similar acts”).
Individuals committed under the civil commitment statute may be released by the treating facility prior to expiration of the commitment period without court proceedings. RCW 71.05.260, .330, and .340.
. A criminal defendant must plead and establish by a preponderance of the evidence the defense of insanity. RCW 10.77.030, as amended by Laws of 1974, 1st Ex. Sess., ch. 198, § 3, p. 786. The court or jury must make special findings stating whether the defendant committed the. act charged, whether he or she is acquitted “because of insanity.existing at the time of the act charged,” whether he or she is “a substantial danger to other persons unless kept under further control by the court,” whether he or she presents “a substantial likelihood of committing felonious acts jeopardizing public safety or security unless kept under further control,” and whether it is “in the best interests of: the defendant . . . that the defendant be placed in treatment that is less restrictive than detention' in a state mental hospital.” RCW 10.77.040, as amended by Laws of 1974,1st Ex. Sess., ch. 198, § 4, pp. 786-87.
The burden of proof on the issue of commitment at the time of acquittal is unclear from the státute. The burden of proof on the issue of conditional release from commitment *419is also unclear; under RCW 10.77.150, release is possible if the Secretary of the Department of Social and Health Services so recommends, and a reviewing court may deny release “only on the basis of substantial evidence.” RCW 10.77.150, as amended by Laws of 1974, 1st Ex. Sess., ch. 198, § 13, pp. 793-94. The burden of proof at the time of final discharge is on the petitioner (the insanity-acquitted committed person); the standard of proof is a preponderance of evidence. RCW 10.77.200 (2).
The foundation of petitioners’ argument is that since both civil and criminal commitment groups are defined by their potential dangerousness, and the standard to be applied in determining the question of commitment in both cases is the likelihood of future dangerousness, the differences in commitment and release procedures deny equal protection and due process to the group which faces the heavier procedural burden — the insanity-acquitted group. Asserting the two groups to be indistinguishable and the standards to be the same, petitioners contend that equal protection requires that the difference in treatment be justified by its relation to a valid public purpose under a strict scrutiny test. The State, they. argue, must show that a compelling interest is satisfied by subjecting the insanity acquitted to a more burdensome procedure than that confronted by the civilly committed. Apparently because the quantum of dangerousness might be one factor in such a compelling state interest, petitioners argue that the substantial defects in the “dangerousness” standard as a matter of statistics and predictability render it an improper diagnostic and legal determinant.
Petitioners’ argument is cogent, and well presented. We are unable, however, to accept petitioners’ approach. We disagree with the initial premise, and thus must reach a different conclusion. We think the two groups are distinguishable, and are therefore subject to different procedural burdens.
*420Both groups are in the commitment process primarily because of the State’s interest in the safety and security of its citizens. Both statutes indeed attempt to determine dangerousness. Petitioners emphasize that under RCW 71.05.280, as amended in 1974, the civil commitment group includes individuals taken into custody because of “acts constituting a felony,” which the State must show by clear, cogent, and convincing evidence. RCW 71.05.310. Those subject to criminal commitment have been, found beyond a reasonable doubt to have committed an act which, except for their insanity, would have been a criminal act subjecting them to criminal penalties. Furthermore, the jury must find that there is a substantial likelihood that the accused will commit future acts jeopardizing the public safety. We are of the view that the legislature, in drafting these two statutes, contemplated that a prosecutor would proceed by way of criminal charges against persons who have committed serious felonies, reserving the civil process for persons who have committed less serious acts which may amount to felonies. The standard to be applied is one of dangerousness; clearly, past conduct is heavily indicative of the likelihood that a person will commit similar acts which will again endanger others. Therefore, it is logical that those who have reached the attention of the State because of serious antisocial acts, would be subject to more procedural burdens in obtaining their release than are those whose acts are less threatening to the public safety. This latter group is appropriately relieved of such burdens, the responsibility of proving their dangerousness falling accordingly to the State. The distinction in both cases is one of degree; the more serious acts result in a heavier burden on the actor on the issue of whether that person must be confined in the interest of public safety.
We are cognizant that the social and scientific determinants of dangerousness, especially future dangerousness, are far from perfect. However, the State’s interest in the safety of its citizens is strong enough to allow the legisla*421ture some leeway in formulating what are essentially predictive standards. The theory of mental commitment underlying both statutes is twofold: preventive detention, and treatment. Neither statute authorizes commitment and detention on the sole ground of a person’s need for treatment; protection of citizens is the primary justification for the deprivation of an individual’s liberty under these statutes. Protection by prevention requires prediction; under our statutes, prediction is based in part on the fact of prior dangerous acts proved beyond a reasonable doubt. Full due process safeguards surround that proof. The fact that the prediction cannot be foolproof does not discredit the attempt. At this point in the development of our knowledge about human behavior, the dangerousness standard is not an unreasonable one.
Our conclusion that the classes are differently constituted is consistent with our decision in State v. Blubaugh, 80 Wn.2d 28, 491 P.2d 646 (1971), in which we considered differing discharge provisions governing civilly and criminally committed persons under statutes then in effect. We concluded that insanity-acquitted individuals who have been found unsafe to be at large could properly be treated as “ ‘an exceptional class of people.’ ” State v. Blubaugh, supra at 33. We held that equal protection was not violated by subjecting a person committed under the criminal insanity statute to a heavier burden in obtaining release from confinement. We think the Blubaugh reasoning is by analogy applicable here; different procedures are justified in determinations of present dangerousness, whether at the time of initial commitment or at the time of a petition for release from confinement.
The cases principally relied upon by petitioners do not compel another result. Baxstrom v. Herold, 383 U.S. 107, 15 L. Ed. 2d 620, 86 S. Ct. 760 (1966), involved a New York statutory provision allowing for summary commitment of a state prisoner at the end of his or her sentence, without the procedural safeguards of hearing and jury trial accorded
*422before civil-commitment. The. facts of Baxstrom distinguish it readily from the case at hand. As the court stated, in. United States v. Brown, 478 F.2d 606, 612 (D.C. Cir. 1973):
Insofar as Baxstrom pertains to procedures, its spirit may be applicable, to all persons in prison. But insofar as it may govern burden and.standard of proof, it is iimited to persons at the end of the penál term.
(Footnote omitted.)
The provisions of the Washington statute comport with Baxstrom. Under RCW 10.77.020, as amended by Laws of 1974, 1st Ex. Sess., ch. 198, § 2, pp. 785-86, no person may be committed, under the criminal commitment act for a. period exceeding .the maximum, possible .penal, sentence for any offense charged .for .which that person was acquitted by. reason of insanity. At the end of that period if the person is still in need of commitment or treatment; civil commitment proceedings must be instituted.
Petitioners also rely heavily on Jackson v. Indiana, 406 U.S. 715, 32 L. Ed. 2d 435, 92 S. Ct. 1845 (1972). There thfe court was concerned with an involuntary indefinite commitment based solely on incompetency to stand trial on criminal charges. The mere filing of criminal charges waá held insufficient to justify different treatment for purposes of indefinite commitment. The present petitions do not raise an issue of indefinite commitment prior to judicial determination as to commission of the acts charged. Our statutes do not permit such indefinite commitment based on incompetency to stand trial. RCW 10.77.090, as amended by Laws of 1974, 1st Ex. Sess., ch. 198, § 8, pp. 789-91.
Finally, petitioners rely heavily on Bolton v. Harris, 395 F.2d 642 (D.C. Cir. 1968), in which the District of Columbia Court of Appeals held that an insanity-acquitted individual could not automatically be committed but must be accorded procedures substantially similar, to those in civil commitment proceedings; That court relied on Baxstrom for .the proposition that “commission of criminal acts does not give rise to a presumption, of -dangerousness. which,., standing *423alone, justifies substantial difference in commitment procedures and confinement conditions for the mentally ill.” Bolton v. Harris, supra at 647. The court held that “persons found not guilty by reason of insanity must be given a judicial hearing with procedures substantially similar to those in civil commitment proceedings.” Bolton v. Harris, supra at 651. The court acknowledged that the insanity acquitted could be treated differently from the civilly committed “to the extent that there are relevant differences between these two groups.” Bolton v. Harris, supra at 651. The court upheld the statute requiring court review before release of the criminally committed when no such review was required for civilly committed. However, the court found that where habeas corpus was used as an alternative method of establishing eligibility for release, the burden of proof should be the same for civilly and criminally committed patients, stating: “While the criminal acts committed by a [criminally committed] patient may be evidence indicating whether or not the burden has been met, they do not justify a different burden.” Bolton v. Harris, supra at 653.
We do not reach the same conclusion as . did the Bolton court, and we note that a subsequent case from that court, United States v. Brown, supra, represents a substantial retreat from the Bolton holding. The court in Brown considered arguments similar to those advanced here, and found justification for a more lenient commitment standard for the insanity acquitted, stating:
The difference between the classes for purposes of burden of proof, is in the extent of possibility and consequence of error. If there is error in a determination of mental illness that results in a civil commitment, a person may be deprived of liberty although he never posed any harm to society. If there is a similar error in confinement of an insanity-acquitted individual, there is not only the fact of harm already done, but. the substantial prospect that the same error, ascribing the quality of mental disease to a less extreme deviance, resulted in a legal exculpation where there should have been legal responsibility for the antisocial action.
United States v. Brown, supra at 611.
*424We conclude then that the cases relied upon by petitioners are factually distinguishable from the present case, and are therefore not controlling. We adhere to our earlier decision in Blubaugh; and, based on our presumption of legislative intent, we consider the insanity-acquitted group to be “ ‘an exceptional class of people’ ” who have committed serious felonies and have raised the spectre of their, own potential dangerousness by successfully advancing an insanity defense. This group is distinguishable from those committing less serious acts which nevertheless constitute a felony. We thus find permissible, if not artful, the statutory provisions relating to commitment and release of the insanity-acquitted individual.
Accordingly, the petitions are denied.
Finley, Hunter, Wright, and Brachtenbach, JJ., concur. Stafford, C. J., concurs in the result.The individual facts of each petition are varied, as are' the statutes in effect when each petitioner was originally acquitted and committed. The detailed facts-are, however, not relevant .to the determination- of these petitions. The challenge is to the present statutory scheme.
The relevant statutes are RCW 10.77, as amended by Laws of 1974, 1st Ex. Sess., ch. 198, and RCW 71.05, as amended by Laws of 1974, 1st Ex. Sess., ch. 145.
Subsection (c) of RCW 71.05.320(2), as amended, refers to RCW 71.05.290 (3), which provides:
“(3) If a person has been determined to be incompetent (and the charges have been dismissed) [sic] without prejudice pursuant to RCW 10.77.090(3) (or its successors), then the professional person in charge of the treatment facility or his professional designee may directly file a petition for ninety day treatment under RCW 71.05.280(1). No petition for initial detention or fourteen day detention is required before such a petition may be filed.”