In Maleng v. Cook, 490 U.S. 488 (1989), the habeas petitioner, Cook, was convicted of robbery in 1958 and sentenced to twenty years imprisonment. Id., 489. While on parole from that sentence, he was convicted of assault and of aiding a prisoner to escape, and he was sentenced by the state of Washington in connection with those convictions in 1978. Id. At about the same time, Cook was convicted in federal court of robbery and conspiracy. He was to serve his 1978 state court sentences after completing his federal term of imprisonment. Id. In 1985, while serving his federal term, Cook filed a petition for federal habeas corpus relief in which he attacked his 1958 state conviction and also alleged that the 1958 conviction was used illegally to enhance his 1978 state sentences, which he had not yet begun to serve. Id., 490. The United States Supreme Court concluded that Cook was not "in custody" under the 1958 sentence and therefore could not directly challenge the conviction underlying that sentence. Id. In reaching this conclusion, the court stated that it had "never held . . . that a habeas petitioner may be 'in custody' under a conviction when the sentence imposed for that conviction has fully expired at the time his petition is filed." Id., 491. Moreover, the court held that the potential use of the conviction to enhance a sentence for subsequent offenses did not suffice to render a person "in custody" within the meaning of the habeas statute. Id., 492. Interpreting the "in custody" requirement of 28 U.S.C. 2241 (c)(3), the Court held that "once the sentence imposed for a state conviction has completely expired, the collateral consequences of that conviction are not themselves sufficient to render an individual 'in custody' for the purposes of federal habeas attack upon it." Id. at 492. Such "collateral consequences" include the fact that the expired conviction "has been used to enhance the length of a current or future sentence imposed for a subsequent conviction." Id. at 491. In discussing the federal habeas corpus statute giving federal district courts jurisdiction to entertain petitions for habeas corpus "only from persons who are 'in custody in violation of the Constitution or laws or treaties of the United States,' " the Supreme Court observed it had "interpreted the statutory language as requiring that the habeas petitioner be 'in custody' under the conviction or sentence under attack at the time his petition is filed." (Id. at pp. 490-491.) The Supreme Court also observed that its "interpretation of the 'in custody' language has not required that a prisoner be physically confined in order to challenge his sentence on habeas corpus. . . . For example, we held that a prisoner who had been placed on parole was still 'in custody' under his expired sentence." (Id. at p. 491.) However, the Supreme Court further observed that it had never held that "a habeas petitioner may be 'in custody' under a conviction when the sentence imposed for that conviction has fully expired at the time his petition is filed." (Ibid.) In Maleng v. Cook, supra, 490 U.S. 488, a case involving use of prior convictions to enhance sentences on subsequent convictions, the Supreme Court faced the question "whether a habeas petitioner remains 'in custody' under a conviction after the sentence imposed for it has fully expired, merely because of the possibility that the prior conviction will be used to enhance the sentences imposed for any subsequent crimes of which he is convicted." (Id. at p. 492.) In giving a negative answer to that question, the Supreme Court stated, "While we have very liberally construed the 'in custody' requirement for purposes of federal habeas, we have never extended it to the situation where a habeas petitioner suffers no present restraint from a conviction." (Ibid.) Further, in noting a different conclusion was not required even though in that case "the possibility of a sentence upon a subsequent conviction being enhanced because of the prior conviction actually materialized," the Supreme Court stated, "When the second sentence is imposed, it is pursuant to the second conviction that the petitioner is incarcerated and is therefore 'in custody.' " (Id. at pp. 492-493.)