HASELTON, J.
Plaintiff, an inmate at the Oregon State Penitentiary (OSP), appeals from a judgment dismissing his petition for a writ of habeas corpus. ORS 34.310. He asserts that he is entitled to credit on his Oregon sentence for time served in federal custody on convictions for crimes he committed while on temporary leave during the pendency of his Oregon sentence. We conclude that plaintiff was “voluntarily absent” from Oregon custody, ORS 137.370(3) (1977), and, thus, was not entitled to credit for time spent in federal custody. Consequently, we affirm.
In October 1978, plaintiff was convicted of robbery in the first degree, ORS 164.415, which he committed on or about July 26, 1978. Thereafter, plaintiff was sentenced to the legal and physical custody of the Oregon Department of Corrections (DOC) for a period not to exceed 20 years. The DOC established a statutory good time date of November 22, 1991.
On September 16, 1983, the DOC granted plaintiff temporary transitional leave for the purpose of integrating into the community before his parole release date of January 23,1984. On December 27,1983, pursuant to the conditions of his temporary leave, plaintiff was to report to a parole officer to sign his parole papers. When he arrived at the parole office, and before he signed the papers, federal agents arrested him on a federal robbery charge, a crime he committed while on temporary leave. Plaintiff pleaded guilty to that charge, was sentenced to 20 years in the federal penitentiary, and was immediately transported to Leavenworth, Kansas, where he began serving that sentence.
On December 30, 1983, the Oregon Board of Parole and Post-Prison Supervision (Board) suspended plaintiff’s parole on his Oregon sentence. On October 25, 1984, DOC issued a detainer on plaintiff. On May 19, 1996, 12 years after plaintiff began serving his federal sentence, he was released from federal prison, and, pursuant to the detainer lodged by the DOC, he was returned to the OSP. Upon his return, the DOC established a new good time date of May 21, 2004, and a maximum retention date of January 20, 2011.
[368]*368On April 23, 1997, plaintiff petitioned for a writ of habeas corpus, asserting that (1) his Oregon sentence continued to run while he was in federal custody; and (2) when his time in federal custody was credited against his Oregon sentence, that sentence had been fully served. Defendant filed a return, and plaintiff filed a replication. Defendant moved to dismiss on the ground that plaintiff had failed to state a claim for habeas relief. The trial court denied that motion. After a trial in January 1998, the court denied the writ and entered a judgment of dismissal. This appeal followed.
On appeal, plaintiff asserts that the trial court’s denial of his writ was erroneous. His principal contention is, as it was at trial, that ORS 137.370, which allows for the computation of terms of imprisonment in Oregon penal and correctional institutions, provides grounds for the granting of his writ. Specifically, plaintiff argues that OAR 291-100-013(2)(d) and (e) (1981)1 and the 1981 version of ORS 137.3702 apply, and that under those provisions, his sentence “resumed running when it was officially confirmed that plaintiff was in custody ‘even though he[ ] may be serving a sentence in another institution.’ ” Alternatively, plaintiff asserts that if, as the state contends, the 1977 version of ORS 137.370 applies, then he nonetheless is entitled to relief. We first consider plaintiffs reliance on OAR 291-100-013 (1981) and the 1981 version of ORS 137.370. The trial court concluded, and we agree, that plaintiffs reliance on those provisions is [369]*369misplaced. Because plaintiff committed the Oregon crime for which he is incarcerated in 1978, our analysis is governed by the laws then in effect. See State v. Isom, 313 Or 391, 395, 837 P2d 491 (1992) (“[T]he legislature intends that Oregon courts sentence criminal defendants under the statutory scheme in force when a particular criminal act was committed.”); State v. Flowers, 136 Or App 555, 558, 902 P2d 624 (1995), rev den 324 Or 513 (1997) (same). The 1981 rule was promulgated in response to the 1981 amendments to ORS 137.370. Neither was in effect at the time of plaintiff’s crimes.
Thus, plaintiffs entitlement to relief depends on the proper construction and application of the 1977 version of ORS 137.370(3), which was in effect when plaintiff committed his crime. That statute provided, in part:
“Except as provided in ORS 421.120 and 421.122, no time during which a person sentenced to imprisonment in the penitentiary or the correctional institution is voluntarily absent from the penitentiary or correctional institution can be counted as a part of the term for which such person was sentenced.” ORS 137.370(3) (1977) (emphasis added).
Our analysis and the parties’ arguments focus on the proper construction of that statute, and particularly the meaning of “voluntarily absent” — i.e., whether plaintiffs absence from the OSP while serving a federal sentence was “voluntary” within the meaning of ORS 137.370(3) (1977).
Under the familiar PGE framework, we begin with the text and context of the statute. Context includes prior versions and succeeding changes to the statute, Krieger v. Just, 319 Or 328, 336, 876 P2d 754 (1994), as well as prior judicial interpretations of the relevant language. Stephens v. Bohlman, 314 Or 344, 350 n 6, 838 P2d 600 (1992).
In Strong v. Gladden, 225 Or 345, 350, 358 P2d 520 (1961), the court construed an earlier version of ORS 137.370, which also included the phrase “voluntarily absent.” There, the court considered whether an inmate who spent time away from the penitentiary, and in the custody of Multnomah County during the pendency of post-conviction proceedings, was “voluntarily absent.” The then-operative version of ORS 137.370 provided:
[370]
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HASELTON, J.
Plaintiff, an inmate at the Oregon State Penitentiary (OSP), appeals from a judgment dismissing his petition for a writ of habeas corpus. ORS 34.310. He asserts that he is entitled to credit on his Oregon sentence for time served in federal custody on convictions for crimes he committed while on temporary leave during the pendency of his Oregon sentence. We conclude that plaintiff was “voluntarily absent” from Oregon custody, ORS 137.370(3) (1977), and, thus, was not entitled to credit for time spent in federal custody. Consequently, we affirm.
In October 1978, plaintiff was convicted of robbery in the first degree, ORS 164.415, which he committed on or about July 26, 1978. Thereafter, plaintiff was sentenced to the legal and physical custody of the Oregon Department of Corrections (DOC) for a period not to exceed 20 years. The DOC established a statutory good time date of November 22, 1991.
On September 16, 1983, the DOC granted plaintiff temporary transitional leave for the purpose of integrating into the community before his parole release date of January 23,1984. On December 27,1983, pursuant to the conditions of his temporary leave, plaintiff was to report to a parole officer to sign his parole papers. When he arrived at the parole office, and before he signed the papers, federal agents arrested him on a federal robbery charge, a crime he committed while on temporary leave. Plaintiff pleaded guilty to that charge, was sentenced to 20 years in the federal penitentiary, and was immediately transported to Leavenworth, Kansas, where he began serving that sentence.
On December 30, 1983, the Oregon Board of Parole and Post-Prison Supervision (Board) suspended plaintiff’s parole on his Oregon sentence. On October 25, 1984, DOC issued a detainer on plaintiff. On May 19, 1996, 12 years after plaintiff began serving his federal sentence, he was released from federal prison, and, pursuant to the detainer lodged by the DOC, he was returned to the OSP. Upon his return, the DOC established a new good time date of May 21, 2004, and a maximum retention date of January 20, 2011.
[368]*368On April 23, 1997, plaintiff petitioned for a writ of habeas corpus, asserting that (1) his Oregon sentence continued to run while he was in federal custody; and (2) when his time in federal custody was credited against his Oregon sentence, that sentence had been fully served. Defendant filed a return, and plaintiff filed a replication. Defendant moved to dismiss on the ground that plaintiff had failed to state a claim for habeas relief. The trial court denied that motion. After a trial in January 1998, the court denied the writ and entered a judgment of dismissal. This appeal followed.
On appeal, plaintiff asserts that the trial court’s denial of his writ was erroneous. His principal contention is, as it was at trial, that ORS 137.370, which allows for the computation of terms of imprisonment in Oregon penal and correctional institutions, provides grounds for the granting of his writ. Specifically, plaintiff argues that OAR 291-100-013(2)(d) and (e) (1981)1 and the 1981 version of ORS 137.3702 apply, and that under those provisions, his sentence “resumed running when it was officially confirmed that plaintiff was in custody ‘even though he[ ] may be serving a sentence in another institution.’ ” Alternatively, plaintiff asserts that if, as the state contends, the 1977 version of ORS 137.370 applies, then he nonetheless is entitled to relief. We first consider plaintiffs reliance on OAR 291-100-013 (1981) and the 1981 version of ORS 137.370. The trial court concluded, and we agree, that plaintiffs reliance on those provisions is [369]*369misplaced. Because plaintiff committed the Oregon crime for which he is incarcerated in 1978, our analysis is governed by the laws then in effect. See State v. Isom, 313 Or 391, 395, 837 P2d 491 (1992) (“[T]he legislature intends that Oregon courts sentence criminal defendants under the statutory scheme in force when a particular criminal act was committed.”); State v. Flowers, 136 Or App 555, 558, 902 P2d 624 (1995), rev den 324 Or 513 (1997) (same). The 1981 rule was promulgated in response to the 1981 amendments to ORS 137.370. Neither was in effect at the time of plaintiff’s crimes.
Thus, plaintiffs entitlement to relief depends on the proper construction and application of the 1977 version of ORS 137.370(3), which was in effect when plaintiff committed his crime. That statute provided, in part:
“Except as provided in ORS 421.120 and 421.122, no time during which a person sentenced to imprisonment in the penitentiary or the correctional institution is voluntarily absent from the penitentiary or correctional institution can be counted as a part of the term for which such person was sentenced.” ORS 137.370(3) (1977) (emphasis added).
Our analysis and the parties’ arguments focus on the proper construction of that statute, and particularly the meaning of “voluntarily absent” — i.e., whether plaintiffs absence from the OSP while serving a federal sentence was “voluntary” within the meaning of ORS 137.370(3) (1977).
Under the familiar PGE framework, we begin with the text and context of the statute. Context includes prior versions and succeeding changes to the statute, Krieger v. Just, 319 Or 328, 336, 876 P2d 754 (1994), as well as prior judicial interpretations of the relevant language. Stephens v. Bohlman, 314 Or 344, 350 n 6, 838 P2d 600 (1992).
In Strong v. Gladden, 225 Or 345, 350, 358 P2d 520 (1961), the court construed an earlier version of ORS 137.370, which also included the phrase “voluntarily absent.” There, the court considered whether an inmate who spent time away from the penitentiary, and in the custody of Multnomah County during the pendency of post-conviction proceedings, was “voluntarily absent.” The then-operative version of ORS 137.370 provided:
[370]*370“When a person is sentenced to imprisonment in the penitentiary or the correctional institution, his term of confinement therein commences from the day of his delivery at the penitentiary or correctional institution to the proper officer thereof, and no time during which such person is voluntarily absent therefrom can be counted as a part of the term for which such person was sentenced.” Or Laws 1955, ch 660, § 15 (emphasis added).
The court concluded that the inmate was not “voluntarily absent” for purposes of the statute:
“The words ‘voluntarily absent’ refer to a prisoner who is absent from the penitentiary unlawfully.
“[ORS 138.620, pertaining to post-conviction proceedings,] seems quite clear that whenever a prisoner as plaintiff is ordered to be present in court he is lawfully absent from the penitentiary whether the court acts on a motion of the plaintiff or on its own motion. Nowhere in the statutes relating to post-conviction relief do we find any implication that the execution of the sentence is stayed while such proceedings are pending, such as is provided in ORS 138.130 pending an appeal to this court from a judgment of conviction.” Strong, 225 Or at 350-51.
Despite Strong’s construction of the statute, the state argues that the “rule of prior construction,” see, e.g., Stephens, 314 Or at 350 n 6, does not apply because post-Strong amendments to ORS 137.370 “necessarily changed the proper interpretation of the phrase ‘voluntarily absent.’ ” We disagree. We presume that the legislature, in enacting amendments to a statute, is aware of the Supreme Court’s prior decisions interpreting that statute, see State v. Cleven-ger, 297 Or 234, 244, 683, P2d 1360 (1984), and we will not presume that amendments change the meaning of preexisting language further than is expressly declared or necessarily implied. See Jones v. General Motors Corp., 325 Or 404, 414-15, 939 P2d 608 (1997). The post -Strong amendments to ORS 137.370 did not alter the essential “voluntarily absent” language. Rather, those amendments excepted certain inmate educational and employment programs conducted [371]*371outside the penitentiary from the general provision that “voluntary absences” suspend the running of a sentence.3 Thus, those amendments amplified and clarified that specific types of absences from the penitentiaiy were not “voluntary.” They did not alter Strong’s basic construction that to be “voluntarily absent” an inmate must be “unlawfully absent.” See Strong, 225 Or at 350.
Thus, the issue reduces to the meaning of “unlawfully absent.” The parties offer two contending constructions. Plaintiff asserts that his absence from Oregon custody was not “voluntary” in that his arrest by federal officials in his parole officer’s office was “beyond his control — as was his placement in a federal prison in Kansas.” Thus, he argues, he performed no “affirmative action” and was not “voluntarily absent” from Oregon custody. The state counters that plaintiffs absence was the result of his own unlawful conduct— i.e., robbery committed while on temporary leave that resulted in his arrest and incarceration by federal authorities — and that he was, thus, unlawfully absent. Consequently, he was “voluntarily absent.”
We agree with the state. Although plaintiff was in federal custody — and, conversely, absent from state custody-pursuant to a lawful judgment, the federal conviction and judgment were the direct consequence of plaintiffs own unlawful conduct while serving his Oregon sentence. That is, the essential and precipitating cause of plaintiffs absence from Oregon custody was his own voluntary and unlawful conduct. In that regard, plaintiffs situation is analogous to that of an inmate who escaped from Oregon custody, committed a crime in another state while on escape status, was convicted and incarcerated in the other state, and then sought to credit the time served in the other state against the Oregon sentence from which he had escaped. If plaintiffs construction were correct, then that hypothetical inmate would be entitled to credit for time served in the other state. In both the hypothetical and this case, if plaintiffs construction were endorsed, then Oregon’s valid penal interest in full service of [372]*372the Oregon sentence would be frustrated by the inmate-plaintiffs voluntary and unlawful conduct. We thus reject that construction.
We conclude that, for purposes of ORS 137.370(3) (1977), when a person is absent from Oregon custody because of unlawful conduct committed during the term of an Oregon sentence, that person is “voluntarily absent.” Plaintiff was not entitled to a credit for his time in federal custody.4
Affirmed.