JUSTICE POWELL delivered the opinion of the Court.The question presented is whether petitioner, who was committed to a mental hospital upon being acquitted of a criminal offense by reason of insanity, must be released because he has been hospitalized for a period longer than he might have served in prison had he been convicted.IIn the District of Columbia, a criminal defendant may be acquitted by reason of insanity if his insanity is "affirmatively established by a preponderance of the evidence."  D.C.Code § 24-301(j) (1981). [Footnote 1]  If he successfully invokes the insanity defense, he is committed to a mental hospital.  § 24-301(d)(1). [Footnote 2]  The statute provides several ways of obtaining Page 463 U. S. 357 release.  Within 50 days of commitment, the acquittee is entitled to a judicial hearing to determine his eligibility for release, at which he has the burden of proving by a preponderance of the evidence that he is no longer mentally ill or dangerous.  § 24-301(d)(2). [Footnote 3]  If he fails to meet this burden at the 50-day hearing, the committed acquittee subsequently may be released, with court approval, upon certification of his recovery by the hospital chief of service.  § 24-301(e). [Footnote 4]  Page 463 U. S. 358 Alternatively, the acquittee is entitled to a judicial hearing every six months at which he may establish by a preponderance of the evidence that he is entitled to release.  § 24-301(k). [Footnote 5]Independent of its provision for the commitment of insanity acquitees, the District of Columbia also has adopted a civil commitment procedure, under which an individual may be committed upon clear and convincing proof by the Government Page 463 U. S. 359 that he is mentally ill and likely to injure himself or others.  § 21-545(b). [Footnote 6]  The individual may demand a jury in the civil commitment proceeding. § 21-544.  Once committed, a patient may be released at any time upon certification of recovery by the hospital chief of service.  §§ 21-546, 21-548.  Alternatively, the patient is entitled after the first 90 days, and subsequently at 6-month intervals, to request a judicial hearing at which he may gain his release by proving by a preponderance of the evidence that he is no longer mentally ill or dangerous.  §§ 21-546, 21-547; see Dixon v. Jacobs, 138 U.S.App.D.C. 319, 328, 427 F.2d 589, 598 (1970).IIOn September 19, 1975, petitioner was arrested for attempting to steal a jacket from a department store.  The next day, he was arraigned in the District of Columbia Superior Court on a charge of attempted petit larceny, a misdemeanor punishable by a maximum prison sentence of one year.  §§ 22-103, 22-2202.  The court ordered petitioner committed to St. Elizabeths, a public hospital for the mentally ill, for a determination of his competency to stand trial. [Footnote 7]  On March 1, 1976, a hospital psychologist submitted a report to the court stating that petitioner was competent to stand trial, that petitioner suffered from "Schizophrenia, paranoid Page 463 U. S. 360 type," and that petitioner's alleged offense was "the product of his mental disease."  Record 51.  The court ruled that petitioner was competent to stand trial.  Petitioner subsequently decided to plead not guilty by reason of insanity.  The Government did not contest the plea, and it entered into a stipulation of facts with petitioner.  On March 12, 1976, the Superior Court found petitioner not guilty by reason of insanity and committed him to St. Elizabeths pursuant to § 24-301(d)(1).On May 25, 1976, the court held the 50-day hearing required by § 24-301(d)(2)(A).  A psychologist from St. Elizabeths testified on behalf of the Government that, in the opinion of the staff, petitioner continued to suffer from paranoid schizophrenia, and that, "because his illness is still quite active, he is still a danger to himself and to others."  Tr. 9.  Petitioner's counsel conducted a brief cross-examination, and presented no evidence. [Footnote 8]  The court then found that"the defendant-patient is mentally ill and, as a result of his mental illness, at this time, he constitutes a danger to himself or others."Id. at 13.  Petitioner was returned to St. Elizabeths.  Petitioner obtained new counsel and, following some procedural confusion, a second release hearing was held on February 22, 1977.  By that date, petitioner had been hospitalized for more than one year, the maximum period he could have spent in prison if he had been convicted.  On that basis, he demanded that he be released unconditionally or recommitted pursuant to the civil commitment standards in § 21545(b), including a jury trial and proof by clear and convincing evidence of his mental illness and dangerousness.  The Superior Court denied petitioner's request for a civil commitment hearing, reaffirmed the findings made at the Page 463 U. S. 361 May 25, 1976, hearing, and continued petitioner's commitment to St. Elizabeths. [Footnote 9]Petitioner appealed to the District of Columbia Court of Appeals.  A panel of the court affirmed the Superior Court, 396 A.2d 183 (1978), but then granted rehearing and reversed, 411 A.2d 624 (1980).  Finally, the court heard the case en banc and affirmed the judgment of the Superior Court.  432 A.2d 364 (1981).  The Court of Appeals rejected the argument"that the length of the prison sentence [petitioner] might have received determines when he is entitled to release or civil commitment under Title 24 of the D.C.Code."Id. at 368.  It then held that the various statutory differences between civil commitment and commitment of insanity acquitees were justified under the equal protection component of the Fifth Amendment.  Id. at 371-376.We granted certiorari, 454 U.S. 1141 (1982), and now affirm.IIIIt is clear that "commitment for any purpose constitutes a significant deprivation of liberty that requires due process protection."  Addington v. Texas, 441 U. S. 418,  441 U. S. 425 (1979).  Therefore, a State must have "a constitutionally adequate purpose for the confinement."  O'Connor v. Donaldson, 422 U. S. 563,  422 U. S. 574 (1975).  Congress has determined that a criminal defendant found not guilty by reason of insanity in the District of Columbia should be committed indefinitely to a mental institution for treatment and the protection of society.  See H.R.Rep. No. 91-907, pp. 73-74 (1970); 432 A.2d  at 371 ("[T]he District of Columbia statutory scheme for commitment Page 463 U. S. 362 of insane criminals is . . . a regulatory, prophylactic statute, based on a legitimate governmental interest in protecting society and rehabilitating mental patients").  Petitioner does not contest the Government's authority to commit a mentally ill and dangerous person indefinitely to a mental institution, but rather contends that "the petitioner's trial was not a constitutionally adequate hearing to justify an indefinite commitment."  Brief for Petitioner 14.Petitioner's argument rests principally on Addington v. Texas, supra, in which the Court held that the Due Process Clause requires the State in a civil commitment proceeding to demonstrate by clear and convincing evidence that the individual is mentally ill and dangerous.  441 U.S. at  441 U. S. 426-427.  Petitioner contends that these due process standards were not met in his case, because the judgment of not guilty by reason of insanity did not constitute a finding of present mental illness and dangerousness and because it was established only by a preponderance of the evidence. [Footnote 10]  Petitioner Page 463 U. S. 363 then concludes that the Government's only conceivably legitimate justification for automatic commitment is to ensure that insanity acquitees do not escape confinement entirely, and that this interest can justify commitment at most for a period equal to the maximum prison sentence the acquittee could have received if convicted.  Because petitioner has been hospitalized for longer than the one year he might have served in prison, he asserts that he should be released unconditionally or recommitted under the District's civil commitment procedures. [Footnote 11]AWe turn first to the question whether the finding of insanity at the criminal trial is sufficiently probative of mental illness and dangerousness to justify commitment.  A verdict of not guilty by reason of insanity establishes two facts:  (i) the defendant committed an act that constitutes a criminal offense, and (ii) he committed the act because of mental illness.  Page 463 U. S. 364 Congress has determined that these findings constitute an adequate basis for hospitalizing the acquittee as a dangerous and mentally ill person.  See H.R.Rep. No. 91-907, supra, at 74 (expressing fear that "dangerous criminals, particularly psychopaths, [may] win acquittals of serious criminal charges on grounds of insanity" and yet "escape hospital commitment"); S.Rep. No. 1170, 84th Cong., 1st Sess., 13 (1955) ("Where [the] accused has pleaded insanity as a defense to a crime, and the jury has found that the defendant was, in fact, insane at the time the crime was committed, it is just and reasonable in the Committee's opinion that the insanity, once established, should be presumed to continue and that the accused should automatically be confined for treatment until it can be shown that he has recovered").  We cannot say that it was unreasonable, and therefore unconstitutional, for Congress to make this determination.The fact that a person has been found, beyond a reasonable doubt, to have committed a criminal act certainly indicates dangerousness. [Footnote 12]  See Lynch v. Overholser, 369 U. S. 705,  369 U. S. 714 (1962) (The fact that the accused was found to have committed a criminal act is "strong evidence that his continued liberty could imperil the preservation of public peace'").  Indeed, this concrete evidence generally may be at least as persuasive as any predictions about dangerousness that might be made in a civil commitment proceeding. [Footnote 13]  We do not agree Page 463 U. S. 365 with petitioner's suggestion that the requisite dangerousness is not established by proof that a person committed a nonviolent crime against property.  This Court never has held that "violence," however that term might be defined, is a prerequisite for a constitutional commitment. [Footnote 14] Page 463 U. S. 366Nor can we say that it was unreasonable for Congress to determine that the insanity acquittal supports an inference of continuing mental illness.  It comports with common sense to conclude that someone whose mental illness was sufficient to lead him to commit a criminal act is likely to remain ill and in need of treatment.  The precise evidentiary force of the insanity acquittal, of course, may vary from case to case, but the Due Process Clause does not require Congress to make classifications that fit every individual with the same degree of relevance.  See Marshall v. United States, 414 U. S. 417,  414 U. S. 428 (1974).  Because a hearing is provided within 50 days of the commitment, there is assurance that every acquittee has prompt opportunity to obtain release if he has recovered.Petitioner also argues that, whatever the evidentiary value of the insanity acquittal, the Government lacks a legitimate reason for committing insanity acquitees automatically because it can introduce the insanity acquittal as evidence in a subsequent civil proceeding.  This argument fails to consider the Government's strong interest in avoiding the need to conduct a de novo commitment hearing following every insanity acquittal -- a hearing at which a jury trial may be demanded, § 21-544, and at which the Government bears the burden of proof by clear and convincing evidence.  Instead of focusing on the critical question whether the acquittee has recovered, the new proceeding likely would have to relitigate much of the criminal trial.  These problems accent the Government's important interest in automatic commitment.  See Mathews v. Eldridge, 424 U. S. 319,  424 U. S. 348 (1976).  We therefore conclude that a finding of not guilty by reason of insanity is a sufficient foundation for commitment of an insanity acquittee for the purposes of treatment and the protection of society.BPetitioner next contends that his indefinite commitment is unconstitutional because the proof of his insanity was based only on a preponderance of the evidence, as compared to Page 463 U. S. 367 Addington's civil commitment requirement of proof by clear and convincing evidence.  In equating these situations, petitioner ignores important differences between the class of potential civil commitment candidates and the class of insanity acquitees that justify differing standards of proof.  The Addington Court expressed particular concern that members of the public could be confined on the basis of"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."441 U.S. at  441 U. S. 426-427.  See also O'Connor v. Donaldson, 422 U.S. at  422 U. S. 575.  In view of this concern, the Court deemed it inappropriate to ask the individual "to share equally with society the risk of error."  Addington, 441 U.S. at  441 U. S. 427.  But since automatic commitment under § 24-301(d)(1) follows only if the acquittee himself advances insanity as a defense and proves that his criminal act was a product of his mental illness, [Footnote 15] there is good reason for diminished concern as to the risk of error. [Footnote 16]  More important, the proof that he committed a criminal act as a result of mental illness eliminates the risk that he is being committed for mere "idiosyncratic behavior," Addington, 441 U.S. at  441 U. S. 427.  A criminal act, by definition, is not "within a range of conduct that is generally acceptable."  Id. at  441 U. S. 426-427.We therefore conclude that concerns critical to our decision in Addington are diminished or absent in the case of insanity acquitees.  Accordingly, there is no reason for adopting the same standard of proof in both eases.  "[D]ue process is flexible, and calls for such procedural protections as the particular Page 463 U. S. 368 situation demands."  Morrissey v. Brewer, 408 U. S. 471,  408 U. S. 481 (1972).  The preponderance of the evidence standard comports with due process for commitment of insanity acquitees. [Footnote 17]CThe remaining question is whether petitioner nonetheless is entitled to his release because he has been hospitalized for a period longer than he could have been incarcerated if convicted.  The Due Process Clause"requires that the nature and duration of commitment bear some reasonable relation to the purpose for which the individual is committed."Jackson v. Indiana, 406 U. S. 715,  406 U. S. 738 (1972).  The purpose of commitment following an insanity acquittal, like that of civil commitment, is to treat the individual's mental illness and protect him and society from his potential dangerousness.  The committed acquittee is entitled to release when he has recovered his sanity or is no longer dangerous.  See O'Connor v. Donaldson, supra, at  422 U. S. 575-576; 432 A.2d  at 372, and n. 16; H.R.Rep. No. 91-907, pp. 73-74 (1970).  And because it is impossible to predict how long it will take for any given individual to recover -- or indeed whether he ever will recover -- Congress has chosen, as it has with respect to civil commitment, to leave the length of commitment indeterminate, subject to periodic review of the patient's suitability for release.In light of the congressional purposes underlying commitment of insanity acquitees, we think petitioner clearly errs in contending that an acquittee's hypothetical maximum sentence provides the constitutional limit for his commitment.  A particular sentence of incarceration is chosen to reflect society's view of the proper response to commission of a particular Page 463 U. S. 369 criminal offense, based on a variety of considerations such as retribution, deterrence, and rehabilitation.  See, e.g., Gregg v. Georgia, 428 U. S. 153,  428 U. S. 183-186 (1976) (opinion of Stewart, POWELL, and STEVENS, JJ.); Kennedy v. Mendoza-Martinez, 372 U. S. 144,  372 U. S. 168 (1963); Williams v. New York, 337 U. S. 241,  337 U. S. 248-249 (1949).  The State may punish a person convicted of a crime even if satisfied that he is unlikely to commit further crimes.Different considerations underlie commitment of an insanity acquittee.  As he was not convicted, he may not be punished. [Footnote 18]  His confinement rests on his continuing illness and dangerousness.  Thus, under the District of Columbia statute, no matter how serious the act committed by the acquittee, he may be released within 50 days of his acquittal if he has recovered.  In contrast, one who committed a less serious act may be confined for a longer period if he remains ill and dangerous.  There simply is no necessary correlation between severity of the offense and length of time necessary for recovery.  The length of the acquittee's hypothetical criminal sentence therefore is irrelevant to the purposes of his commitment. [Footnote 19] Page 463 U. S. 370IVWe hold that, when a criminal defendant establishes by a preponderance of the evidence that he is not guilty of a crime by reason of insanity, the Constitution permits the Government, on the basis of the insanity judgment, to confine him to a mental institution until such time as he has regained his sanity or is no longer a danger to himself or society.  This holding accords with the widely and reasonably held view that insanity acquitees constitute a special class that should be treated differently from other candidates for commitment. [Footnote 20]  We have observed before that,"[w]hen Congress undertakes to act in areas fraught with medical and scientific uncertainties, legislative options must be especially broad, and courts should be cautious not to rewrite legislation. . . ."Marshall v. United States, 414 U.S. at  414 U. S. 427.  This admonition has particular force in the context of legislative efforts to deal with the special problems raised by the insanity defense.The judgment of the District of Columbia Court of Appeals isAffirmed
U.S. Supreme CourtJones v. United States, 463 U.S. 354 (1983)Jones v. United StatesNo. 81-5195Argued November 2, 1982Decided June 29, 1983463 U.S. 354SyllabusUnder the District of Columbia Code, a criminal defendant may be acquitted by reason of insanity if his insanity is affirmatively established by a preponderance of the evidence.  He is then committed to a mental hospital and within 50 days thereafter is entitled to a judicial hearing to determine his eligibility for release, at which he has the burden of proving by a preponderance of the evidence that he is no longer mentally ill or dangerous.  The Code also provides that the acquittee is entitled to a judicial hearing every six months at which he may establish by a preponderance of the evidence that he is entitled to release.  Petitioner was charged in the District of Columbia Superior Court with attempted petit larceny, a misdemeanor punishable by a maximum prison sentence of one year.  The Superior Court found petitioner not guilty by reason of insanity and committed him to a mental hospital.  At his subsequent 50-day hearing, the court found that he was mentally ill and constituted a danger to himself or others.  A second release hearing was held after petitioner had been hospitalized for more than one year, the maximum period he could have spent in prison if he had been convicted.  On that basis, he demanded that he be released unconditionally or recommitted pursuant to the civil commitment procedures under the District of Columbia Code, including a jury trial and clear and convincing proof by the Government of his mental illness and dangerousness.  The Superior Court denied his request for a civil commitment hearing, reaffirmed the findings made at the 50-day hearing, and continued his commitment. The District of Columbia Court of Appeals ultimately affirmed.Held:  When a criminal defendant establishes by a preponderance of the evidence that he is not guilty of a crime by reason of insanity, the Constitution permits the Government, on the basis of the insanity judgment, to confine him to a mental institution until such time as he has regained his sanity or is no longer a danger to himself or society.  Pp.  463 U. S. 361-370.(a) A verdict of not guilty by reason of insanity is sufficiently probative of mental illness and dangerousness to justify commitment of the acquittee for the purposes of treatment and the protection of society.  Such a verdict establishes that the defendant committed an act constituting a criminal offense, and that he committed the act because of mental Page 463 U. S. 355 illness.  It was not unreasonable for Congress to determine that these findings constitute an adequate basis for hospitalizing the acquittee as a dangerous and mentally ill person.  The fact that a person has been found, beyond a reasonable doubt, to have committed a criminal act certainly indicates dangerousness.  Nor is it unreasonable to conclude that an insanity acquittal supports an inference of continuing mental illness.  The 50-day hearing assures that every acquittee has prompt opportunity to obtain release if he has recovered.  Pp.  463 U. S. 363-366.(b) Indefinite commitment of an insanity acquittee, based on proof of insanity by only a preponderance of the evidence, comports with due process.  Addington v. Texas, 441 U. S. 418, held that the government, in a civil commitment proceeding, must demonstrate by clear and convincing evidence that the individual is mentally ill and dangerous.  However, the concerns critical to that decision -- based on the risk of error that a person might be committed for mere "idiosyncratic behavior" -- are diminished or absent in the case of insanity acquitees, and do not require the same standard of proof in both cases.  Proof that the acquittee committed a criminal act as a result of mental illness eliminates the risk that he is being committed for mere idiosyncratic behavior.  Pp.  463 U. S. 366-368.(c) An insanity acquittee is not entitled to his release merely because he has been hospitalized for a period longer than he could have been incarcerated if convicted.  The length of a sentence for a particular criminal offense is based on a variety of considerations, including retribution, deterrence, and rehabilitation.  However, because an insanity acquittee was not convicted, he may not be punished.  The purpose of his commitment is to treat his mental illness and protect him and society from his potential dangerousness.  There simply is no necessary correlation between the length of the acquittee's hypothetical criminal sentence and the length of time necessary for his recovery.  Pp.  463 U. S. 368-369.432 A.2d 36, affirmed.POWELL, J., delivered the opinion of the Court, in which BURGER, C.J., and WHITE, REHNQUIST, and O'CONNOR, JJ., joined.  BRENNAN, J., filed a dissenting opinion, in which MARSHALL and BLACKMUN, JJ., joined, post, p.  463 U. S. 371.  STEVENS, J., fled a dissenting opinion, post, p.  463 U. S. 387. Page 463 U. S. 356