Justice Thomas
delivered the opinion of the Court.
In 1981, the State of California amended its parole procedures to allow the Board of Prison Terms to decrease the frequency of parole suitability hearings under certain circumstances. This case presents the question whether the application of this amendment to prisoners who committed their crimes before it was enacted violates the Ex Post Facto Clause. We conclude that it does not.
I
California twice has convicted respondent Jose Ramon Morales of murder. In 1971, the body of respondent’s girlfriend, Gina Wallace, was found in an abandoned medical building. She had been shot in the head, neck, and abdomen; her right thumb had been amputated and her face slashed repeatedly. A bloody fingerprint near the body matched respondent’s. A jury found respondent guilty of first-degree murder, and he was sentenced to life in prison.
While serving his sentence at the State Training Facility in Soledad, California, respondent met Lois Washabaugh, a 75-year-old woman who had begun visiting inmates after gaining an interest in prison reform. Ms. Washabaugh visited respondent on numerous occasions, and respondent kept in contact with her through correspondence. Respondent’s letters eventually expressed a romantic interest in Ms. Washabaugh, and the two were married some time after respondent’s release to a halfway house in April 1980.
On July 4, 1980, Ms. Washabaugh left her home and told friends that she was moving to Los Angeles to live with her new husband. Three days later, police officers found a human hand on the Hollywood Freeway in Los Angeles. Ms. Washabaugh was reported missing at the end of July, and fingerprint identification revealed that the hand was hers. Her body was never recovered. Respondent was subsequently arrested and found in possession of Ms. Washabaugh’s car, purse, credit cards, and diamond rings.
Respondent pleaded nolo contendere to the second-degree murder of Ms. Washabaugh. He was sentenced to a term of 15 years to life, but became eligible for parole beginning in 1990. As required by California law, see Cal. Penal Code Ann. § 3041 (West 1982), the Board of Prison Terms (Board) held a hearing on July 25, 1989, to determine respondent’s suitability for parole. California law required the Board to set a release date for respondent unless it found that “the public safety requires a more lengthy period of incarceration for this individual.” § 3041(b). The Board found respondent unsuitable for parole for numerous reasons, including the heinous, atrocious, and cruel nature of his offense; the mutilation of Ms. Washabaugh during or after the murder; respondent’s record of violence and assaultive behavior; and respondent’s commission of his second murder while on parole for his first. Supplemental App. to Pet. for Cert. 45.
Under the law in place at the time respondent murdered Ms. Washabaugh, respondent would have been entitled to subsequent suitability hearings on an annual basis. 1977 Cal. Stats., ch. 165, §46. In 1981, however, the California Legislature had authorized the Board to defer subsequent suitability hearings for up to three years if the prisoner has been convicted of “more than one offense which involves the taking of a life” and if the Board “finds that it is not reasonable to expect that parole would be granted at a hearing during the following years and states the bases for the finding.” Cal. Penal Code Ann. § 3041.5(b)(2) (West 1982). In light of the considerations that led it to find respondent unsuitable for parole, and based on its conclusion that a longer period of observation was required before a parole release date could be projected, the Board determined that it was not reasonable to expect that respondent would be found suitable for parole in 1990 or 1991. Pursuant to the 1981 amendment, the Board scheduled the next hearing for 1992.
Respondent then filed a federal habeas corpus petition in the United States District Court for the Central District of California, asserting that he was being held in custody in violation of the Federal Constitution. See 28 U. S. C. § 2254. Respondent argued that as applied to him, the 1981 amendment constituted an ex post facto law barred by Article I, § 10, of the United States Constitution. The District Court denied respondent’s habeas petition, but the United States Court of Appeals for the Ninth Circuit reversed. 16 F. 3d 1001 (1994). Because “a prisoner cannot be paroled without first having a parole hearing,” the Court of Appeals concluded that “any retrospective law making parole hearings less accessible would effectively increase the [prisoner’s] sentence and violate the ex post facto clause.” Id., at 1004. The Court of Appeals accordingly held that the Board was constitutionally constrained to provide respondent with annual parole suitability hearings, as required by the law in effect when he committed his crime. Id., at 1006.
We granted certiorari, 512 U. S. 1287 (1994), and we now reverse.
II
Article I, §10, of the Constitution prohibits the States from passing any “ex post facto Law.” In Collins v. Youngblood, 497 U. S. 37, 41 (1990), we reaffirmed that the Ex Post Facto Clause incorporated “a term of art with an established meaning at the time of the framing of the Constitution.” In accordance with this original understanding, we have held that the Clause is aimed at laws that “retroactively alter the definition of crimes or increase the punishment for criminal acts.” Id., at 43 (citing Calder v. Bull, 3 Dall. 386, 391-392 (1798) (opinion of Chase, J.); Beazell v. Ohio, 269 U. S. 167, 169-170 (1925)).
The legislation at issue here effects no change in the definition of respondent’s crime. Instead, the question before us is whether the 1981 amendment to §3041.5 increases the “punishment” attached to respondent’s crime. In arguing that it does, respondent relies chiefly on a trilogy of cases holding that a legislature may not stiffen the “standard of punishment” applicable to crimes that have already been committed. See Lindsey v. Washington, 301 U. S. 397, 401 (1937); Miller v. Florida, 482 U. S. 423 (1987); Weaver v. Graham, 450 U. S. 24 (1981).
In Lindsey, we established the proposition that the Constitution “forbids the application of any new punitive measure to a crime already consummated.” 301 U. S., at 401. The petitioners in Lindsey had been convicted of grand larceny, and the sentencing provision in effect at the time they committed their crimes provided for a maximum sentence of “not more than fifteen years.” Id., at 398. The applicable law called for sentencing judges to impose an indeterminate sentence up to whatever maximum they selected, so long as it did not exceed 15 years. Id., at 398, 400. Before the petitioners were sentenced, however, a new statute was passed that required the judge to sentence the petitioners to the 15-year maximum; under the new statute, the petitioners could secure an earlier release only through the grace of the parole board. Id., at 398-399. We held that the application of this statute to petitioners violated the Ex Post Facto Clause because “the measure of punishment prescribed by the later statute is more severe than that of the earlier.” Id., at 401.
Weaver and Miller held that the Ex Post Facto Clause forbids the States to enhance the measure of punishment by altering the substantive “formula” used to calculate the applicable sentencing range. In Weaver, the petitioner had been sentenced to 15 years in prison for his crime of second-degree murder. Both at the time of his crime and at the time his sentence was imposed, state statutes provided a formula for mandatory reductions to the terms of all prisoners who complied with certain prison regulations and state laws. The statute that the petitioner challenged and that we invalidated retroactively reduced the amount of “gain time” credits available to prisoners under this formula. Though the statute preserved the possibility that some prisoners might win back these credits if they convinced prison officials to exercise their discretion to find that they were especially deserving, see 450 U. S., at 34, n. 18, we found that it effectively eliminated the lower end of the possible range of prison terms. Id., at 26-27, 31-33. The statute at issue in Miller contained a similar defect. The Florida sentencing scheme had established “presumptive sentencing ranges” for various offenses, which sentencing judges were required to follow in the absence of “clear and convincing reasons” for a departure. At the time that the petitioner in Miller committed his crime, his presumptive sentencing range would have been 3V2 to 4V2 years. Before his sentencing, however, the state legislature altered the formula for establishing the presumptive sentencing range for certain sexual offenses by increasing the “primary offense points” assigned to those crimes. As a result, petitioner’s presumptive, range jumped to 5V2 to 7 years. We held that the resulting increase in the “quantum of punishment” violated the Ex Post Facto Clause. 482 U. S., at 433-434.
Respondent insists that the California amendment before us is indistinguishable from the legislation at issue in Lindsey, Weaver, and Miller, and he contends that those cases control this one. We disagree. Both before and after the 1981 amendment, California punished the offense of second-degree murder with an indeterminate sentence of “confinement in the state prison for a term of 15 years to life.” Cal. Penal Code Ann. §190 (West 1982). The amendment also left unchanged the substantive formula for securing any reductions to this sentencing range. Thus, although 15 years was the formal “minimum” term of confinement, see ibid., respondent was able to secure a one-third “credit” or reduction in this minimum by complying with prison rules and regulations, see §2931. The amendment had no effect on the standards for fixing a prisoner’s initial date of “eligibility” for parole, see In re Jackson, 39 Cal. 3d 464, 476, 703 P. 2d 100, 108 (1985), or for determining his “suitability” for parole and setting his release date, see Cal. Penal Code Ann. §§3041, 3041.5 (West 1982).
The 1981 amendment made only one change: It introduced the possibility that after the initial parole hearing, the Board would not have to hold another hearing the very next year, or the year after that, if it found no reasonable probability that respondent would be deemed suitable for parole in the interim period. § 3041.5(b)(2). In contrast to the laws at issue in Lindsey, Weaver, and Miller (which had the purpose and effect of enhancing the range of available prison terms, see Miller, supra, at 433-434), the evident focus of the California amendment was merely “ ‘to relieve the [Board] from the costly and time-consuming responsibility of scheduling parole hearings’” for prisoners who have no reasonable chance of being released. In re Jackson, supra, at 473, 703 P. 2d, at 106 (quoting legislative history). Rather than changing the sentencing range applicable to covered crimes, the 1981 amendment simply “alters the method to be followed” in fixing a parole release date under identical substantive standards. See Miller, supra, at 433 (contrasting adjustment to presumptive sentencing range with change in “the method to be followed in determining the appropriate sentence”); see also Dobbert v. Florida, 432 U. S. 282, 293-294 (1977) (contrasting change in the “quantum of punishment” with statute that merely “altered the methods employed in determining whether the death penalty was to be imposed”).
Ill
Respondent nonetheless urges us to hold that the Ex Post Facto Clause forbids any legislative change that has any conceivable risk of affecting a prisoner’s punishment. In his view, there is “no principled way to determine how significant a risk of enhanced confinement is to be tolerated.” Brief for Respondent 39. Our cases have never accepted this expansive view of the Ex Post Facto Clause, and we will not endorse it here.
Respondent’s approach would require that we invalidate any of a number of minor (and perhaps inevitable) mechanical changes that might produce some remote risk of impact on a prisoner’s expected term of confinement. Under respondent’s approach, the judiciary would be charged under the Ex Post Facto Clause with the micromanagement of an endless array of legislative adjustments to parole and sentencing procedures, including such innocuous adjustments as changes to the membership of the Board of Prison Terms, restrictions on the hours that prisoners may use the prison law library, reductions in the duration of the parole hearing, restrictions on the time allotted for a convicted defendant’s right of allocution before a sentencing judge, and page limitations on a defendant’s objections to presentence reports or on documents seeking a pardon from the governor. These and countless other changes might create some speculative, attenuated risk of affecting a prisoner’s actual term of confinement by making it more difficult for him to make a persuasive case for early release, but that fact alone cannot end the matter for ex post facto purposes.
Indeed, contrary to the approach advocated by respondent, we have long held that the question of what legislative adjustments “will be held to be of sufficient moment to transgress the constitutional prohibition” must be a matter of “degree.” Beazell, 269 U. S., at 171. In evaluating the constitutionality of the 1981 amendment, we must determine whether it produces a sufficient risk of increasing the measure of punishment attached to the covered crimes. We have previously declined to articulate a single “formula” for identifying those legislative changes that have a sufficient effect on substantive crimes or punishments to fall within the constitutional prohibition, see ibid., and we have no occasion to do so here. The amendment creates only the most speculative and attenuated possibility of producing the prohibited effect of increasing the measure of punishment for covered crimes, and such conjectural effects are insufficient under any threshold we might establish under the Ex Post Facto Clause. See Dobbert, supra, at 294 (refusing to accept “speculation” that the effective punishment under a new statutory scheme would be “more onerous” than under the old one).
First, the amendment applies only to a class of prisoners for whom the likelihood of release on parole is quite remote. The amendment enabled the Board to extend the time between suitability hearings only for those prisoners who have been convicted of “more than one offense which involves the taking of a life.” Cal. Penal Code Ann. § 3041.5(b)(2) (West 1982). The California Supreme Court has noted that about 90% of all prisoners are found unsuitable for parole at the initial hearing, while 85% are found unsuitable at the second and subsequent hearings. In re Jackson, 39 Cal. 3d, at 473, 703 P. 2d, at 105. In light of these numbers, the amendment “was seen as a means ‘to relieve the [Board] from the costly and time-consuming responsibility of scheduling parole hearings for prisoners who have no chance of being released.’” Ibid, (quoting legislative history).
Second, the Board’s authority under the amendment is carefully tailored to that end. The amendment has no effect on the date of any prisoner’s initial parole suitability hearing; it affects the timing only of subsequent hearings. Accordingly, the amendment has no effect on any prisoner unless the Board has first concluded, after a hearing, not only that the prisoner is unsuitable for parole, but also that “it. is not reasonable to expect that parole would be granted at a hearing during the following years.” Cal. Penal Code Ann. § 3041.5(b)(2) (West 1982). “This is no arbitrary decision,” Morris v. Castro, 166 Cal. App. 3d 33, 38, 212 Cal. Rptr. 299, 302 (1985); the Board must conduct “a full hearing and review” of all relevant facts, ibid., and state the bases for its finding. Cal. Penal Code Ann. § 3041.5(b)(2) (West 1982). Though California law is not entirely clear on this point, the reliability of the Board’s determination may also be enhanced by the possibility of an administrative appeal. See 15 Cal. Admin. Code § 2050 (1994).
Moreover, the Board retains the authority to tailor the frequency of subsequent suitability hearings to the particular circumstances of the individual prisoner. The default requirement is an annual hearing, but the Board may defer the next hearing up to two years more depending on the circumstances. Cal. Penal Code Ann. § 3041.5(b)(2) (West 1982). Thus, a mass murderer who has participated in repeated violent crimes both in prison and while on parole could perhaps expect a 3-year delay between suitability hearings, while a prisoner who poses a lesser threat to the “public safety,” see § 3041(b), might receive only a 2-year delay. In light of the particularized findings required under the amendment and the broad discretion given to the Board, the narrow class of prisoners covered by the amendment cannot reasonably expect that their prospects for early release on parole would be enhanced by the opportunity of annual hearings. For these prisoners, the amendment simply allows the Board to avoid the futility of going through the motions of reannouncing its denial of parole suitability on a yearly basis.
Respondent suggests that there is some chance that the amendment might nevertheless produce an increased term of confinement for some prisoners who might experience a change of circumstances that could render them suitable for parole during the period between their hearings. Brief for Respondent 39. Respondent fails, however, to provide any support for his speculation that the multiple murderers and other prisoners subject to the amendment might experience an unanticipated change that is sufficiently monumental to alter their suitability for release on parole. Even if we assume the possibility of such a change, moreover, there is no reason to conclude that the amendment will have any effect on any prisoner’s actual term of confinement, for the current record provides no basis for concluding that a prisoner who experiences a drastic change of circumstances would be precluded from seeking an expedited hearing from the Board. Indeed, the California Supreme Court has suggested that under the circumstances hypothesized by respondent “the Board could advance the suitability hearing,” In re Jackson, supra, at 475, 703 P. 2d, at 107, and the California Department of Corrections indicates in its brief that the Board’s “practice” is to “review for merit any communication from an inmate asking for an earlier suitability hearing,” Reply Brief for Petitioner 3, n. 1. If the Board’s decision to postpone the hearing is subject to administrative appeal, the controlling regulations also seem to preserve the possibility of a belated appeal. See 15 Cal. Admin. Code §2050 (1994) (time limits for administrative appeals “are directory only and may be extended”). An expedited hearing by the Board — either on its own volition or pursuant to an order entered on an administrative appeal — would remove any possibility of harm even under the hypothetical circumstances suggested by respondent.
Even if a prisoner were denied an expedited hearing, there is no reason to think that such postponement would extend any prisoner’s actual period of confinement. According to the California Supreme Court, the possibility of immediate release after a finding of suitability for parole is largely “theoretica[l],” In re Jackson, 39 Cal. 3d, at 474, 703 P. 2d, at 106; in many cases, the prisoner’s parole release date comes at least several years after a finding of suitability. To the extent that these cases are representative, it follows that “the 'practical effect’ of a hearing postponement is not significant.” Id., at 474, 703 P. 2d, at 106-107. This is because the Board is bound by statute to consider “any sentencing information relevant to the setting of parole release dates” with an eye toward establishing “uniform terms for offenses of similar gravity and magnitude in respect to their threat to the public.” Cal. Penal Code Ann. § 3041(a) (West 1982). Under these standards, the fact that a prisoner had been “suitable” for parole prior to the date of the hearing certainly would be “relevant” to the Board’s decision in setting an actual release date, and the Board retains the discretion to expedite the release date of such a prisoner. Thus, a prisoner who could show that he was “suitable” for parole two years prior to such a finding by the Board might well be entitled to secure a release date that reflects that fact. Such a prisoner’s ultimate date of release would be entirely unaffected by the change in the timing of suitability hearings.
IV
Given these circumstances, we conclude that the California legislation at issue creates only the most speculative and attenuated risk of increasing the measure of punishment attached to the covered crimes. The Ninth Circuit’s judgment that the amendment violates the Ex Post Facto Clause is accordingly reversed.
It is so ordered.
The statute was again amended in 1990 to allow the Board the alternative of deferring hearings for five years if the prisoner has been convicted of more than two murders, Cal. Penal Code Ann. § 3041.5(b)(2)(C) (West Supp. 1994), 1990 Cal. Stats., ch. 1053, and in 1994 to extend that alternative to prisoners convicted of even a single murder, 1994 Cal. Stats., ch. 560. The 5-year deferral applies, however, “only to offenses committed before July 1, 1977, or on or after January 1, 1991,” 1990 Cal. Stats., ch. 1053, and thus appears to have no application to respondent, whose most recent crime was committed in 1980.
During the pendency of this action, respondent appeared before the Board for his 1992 suitability hearing. The Board again found respondent unsuitable and again determined that it was not reasonable to expect that he would be found suitable for parole at the following two annual hearings. Respondent’s next suitability hearing was then set for 1995.
Our opinions in Lindsey, Weaver, and Miller suggested that enhancements to the measure of criminal punishment fall within the ex post facto prohibition because they operate to the “disadvantage” of covered offenders. See Lindsey, 301 U. S., at 401; Weaver, 450 U. S., at 29; Miller, 482 U. S., at 433. But that language was unnecessary to the results in those cases and is inconsistent with the framework developed in Collins v. Youngblood, 497 U. S. 37, 41 (1990). After Collins, the focus of the ex post facto inquiry is not on whether a legislative change produces some ambiguous sort of “disadvantage,” nor, as the dissent seems to suggest, on whether an amendment affects a prisoner’s “opportunity to take advantage of provisions for early release,” see post, at 518, but on whether any such change alters the definition of criminal conduct or increases the penalty by which a crime is punishable.
The dissent proposes a line between those measures that deprive prisoners of a parole hearing and those that “make it more difficult for prisoners to obtain release.” Post, at 524. But this arbitrary line has absolutely no basis in the Constitution. If a delay in parole hearings raises ex post facto concerns, it is because that delay effectively increases a prisoner’s term of confinement, and not because the hearing itself has independent constitutional significance. Other adjustments to mechanisms surrounding the sentencing process should be evaluated under the same standard.
Contrary to the dissent’s suggestion, see post, at 519, we express no view as to the constitutionality of any of a number of other statutes that might alter the timing of parole hearings under circumstances different from those present here.
The dissent suggests that any “speculation” as to the effect of the amendment on prison terms should “ru[n] in the other direction,” post, at 525, but this approach effectively shifts to the State the burden of persuasion as to respondent’s ex post facto claim. Not surprisingly, the dissent identifies no support for its attempt to undo the settled rule that a claimant must bear the risk of nonpersuasion as to the existence of an alleged constitutional violation. Although we have held that a party asserting an ex post facto claim need not carry the burden of showing that he would have been sentenced to a lesser term under the measure or range of punishments in place under the previous statutory scheme, see Lindsey v. Washington, 301 U. S., at 401, we have never suggested that the challenging party may escape the ultimate burden of establishing that the measure of punishment itself has changed. Indeed, elimination of that burden would eviscerate the view of the Ex Post Facto Clause that we reaffirmed in Collins. Just as “[t]he inhibition upon the passage of ex post facto laws does not give a criminal a right to be tried, in all respects, by the law in force when the crime charged was committed,” Gibson v. Mississippi, 162 U. S. 565, 590 (1896), neither does it require that the sentence be carried out under the identical legal regime that previously prevailed.
The dissent mischaracterizes our analysis in suggesting that we somehow have concocted a “reduced” standard of judicial scrutiny for application to “a narrow group as unpopular ... as multiple murderers.” Post, at 522. The ex post facto standard we apply today is constant: It looks to whether a given legislative change has the prohibited effect of altering the definition of crimes or increasing punishments. Our application of that standard necessarily considers a number of factors — including, in this case, that the 1981 amendment targets a group of prisoners whom the California Legislature deemed less likely than others to secure early release on parole — but the constitutional standard is neither “enhanced” nor “reduced” on the basis of societal animosity toward multiple murderers. Cf. ibid.