Charles Laverne Singleton appeals the district court’s2 order denying his petition for writ of habeas corpus. The district court rejected Singleton’s contention that the administration of mandatory antipsy-chotic medication to a prisoner, initially constitutional under Washington v. Harper, 494 U.S. 210, 110 S.Ct. 1028, 108 L.Ed.2d 178 (1990), becomes unconstitutional once an execution date is set because at that time it ceases to be in the prisoner’s medical interest. After a divided panel of this court reversed, Singleton v. Norris, 267 F.3d 859 (8th Cir.2001), we granted the State’s petition for rehearing en banc and vacated the panel opinion. We now affirm the district court’s order.
I.
In 1979, the State of Arkansas convicted Singleton of capital felony murder and aggravated robbery. He received a sentence of death for the murder and a sentence of life imprisonment for the robbery. The facts giving rise to Singleton’s conviction were set forth in the Arkansas Supreme Court’s opinion on direct appeal:
The victim, Mary Lou York, was murdered in York’s Grocery Store at Hamburg on June 1, 1979. She died from loss of blood as a result of two stab wounds in her neck.
The evidence of guilt in this case is overwhelming. Patti Franklin saw her relative Singleton enter York’s Grocery at approximately 7:30 p.m. on the day of the crime. Shortly after he entered Patti heard Mrs. York scream, “Patti go get help, Charles Singleton is killing me.” Patti then ran for help. Another witness, Lenora Howard, observed Singleton exit the store and shortly thereafter witnessed Mrs. York, who was “crying and had blood on her,” come to the front door. Police Officer Strother was the first to arrive at the scene and found Mrs. York lying in a pool of blood in the rear of the store. The officer testified Mrs. York told him that Charles Singleton “came in the store, said this is a robbery, grabbed her around the neck, *1021and went to stabbing her.” She then told Officer Strother that “there’s no way I can be all right, you know I’m not going to make it. I’ve lost too much blood.” Mrs. York was taken to the hospital in an ambulance and was attended by her personal physician, Dr. J.D. Rankin. While en route to the hospital, she told Dr. Rankin several times that she was dying and that Singleton did it. Mrs. York died before reaching the emergency room of the hospital.
Singleton v. State, 274 Ark. 126, 623 S.W.2d 180, 181 (1981). Singleton’s conviction and sentence for capital felony murder were affirmed, but his conviction for the underlying felony of aggravated robbery was set aside. Id.
After Singleton was denied post-conviction relief in state court, his execution was scheduled for June' 4, 1982. Singleton then petitioned the district court for a stay of execution and writ of habeas corpus, raising claims including ineffective assistance of counsel, use of invalid aggravating factors, and that he was incompetent and thus ineligible for execution under Ford v. Wainwright, 477 U.S. 399, 106 S.Ct. 2595, 91 L.Ed.2d 335 (1986). Singleton v. Lockhart, 653 F.Supp. 1114, 1116 (E.D.Ark.1986). The district court sustained the conviction but reversed the sentence of death, holding that the pecuniary gain aggravating factor was invalid since it duplicated a factor in the underlying robbery-murder charge. Id. at 1135-36. On appeal, a panel of this court affirmed the order upholding the conviction, but reversed the order vacating the death sentence. Singleton v. Lockhart, 871 F.2d 1395, 1396 (8th Cir.1989). Because the district court did not reach the Ford claim, it was not at issue on appeal. On remand for reinstatement of the death sentence, Singleton claimed ineffective assistance of counsel at the penalty phase and challenged the constitutionality of the Arkansas death penalty statute. The district court denied the petition and we affirmed. Singleton v. Lockhart, 962 F.2d 1315, 1316 (8th Cir.1992).
In December 1992, Singleton filed an action in state court claiming that he was incompetent and could not be executed. He requested that his treatment with an-tipsychotic drugs be terminated and that a competency examination be held after the effect of the drugs had subsided. In addition, he asked for a declaratory judgment that he was not competent to be executed. The trial court denied his motion, and the Arkansas Supreme Court affirmed. Singleton v. Endell, 316 Ark. 133, 870 S.W.2d 742 (1994). In his second federal habeas petition, filed in 1993 but held in abeyance until the state proceedings concluded, Singleton raised the Ford claim, along with claims of double counting and actual innocence. The district court held two hearings and dismissed his petition. On appeal, Singleton conceded that he was competent because of the an-tipsychotic medication he was taking voluntarily. We affirmed the dismissal of his petition, noting that a future Ford claim based upon changed circumstances was not foreclosed by the decision. Singleton v. Norris, 108 F.3d 872, 874 (8th Cir.1997).
In 1997, the State placed Singleton on an involuntary medication regime after a medication review panel unanimously agreed that he posed a danger to himself and others. After the medication took effect, Singleton’s psychotic symptoms abated. In January 2000, the State scheduled his execution for March 1, 2000. In February 2000, Singleton filed a petition for habeas corpus pursuant to 28 U.S.C. § 2241, arguing that the State could not constitutionally restore his Ford competency through use of forced medication and then execute him. The district court de*1022nied the petition, finding “no evidence in this record that the actions and decisions of the medical personnel involved were in any degree motivated by the desire, purpose or intent to make Mr. Singleton competent so that he could be executed.” Singleton appealed, and we granted a stay of execution.
We ordered a limited remand in March 2000 to answer two remaining questions of fact. First, whether Singleton was Ford-competent prior to the implementation of the Harper mandatory medication order in 1997. Second, whether Singleton would regress into psychosis and become Ford-incompetent if he stopped taking the medication. In answer to the first question, the district court found that Singleton was not Ford-competent at the time the involuntary medication regime began in 1997. The answer to the second question was less clear. The district court found that Singleton would regress into psychosis without medication, but could not say with certainty when psychotic symptoms would resume and whether he would become Ford-incompetent. Although the district court did not make a specific finding as to Singleton’s present competence, Singleton does not argue that under medication he is unaware of his punishment and why he is to be punished.
II.
The posture of this case has changed during the course of this appeal. Singleton was placed under a Harper involuntary medication order in 1997. That order was subject to annual review and was not renewed by Singleton’s doctors in January 2000 while this appeal was pending. Since that time Singleton has taken his medication voluntarily. A case is not moot if there is a “reasonable expectation or a demonstrated probability that the same controversy will recur involving the same complaining party.” Murphy v. Hunt, 455 U.S. 478, 482, 102 S.Ct. 1181, 71 L.Ed.2d 353 (1982) (per curiam) (citation omitted). In Washington v. Harper, the Court held that a live controversy remained even though Harper’s involuntary medication order had lapsed. 494 U.S. at 218-19, 110 S.Ct. 1028. Although Singleton now takes his medication voluntarily, should he refuse to take his medication, the State would be obligated to medicate him to control his psychotic symptoms, thereby reviving his claim. Because the combination of a Harper order and a scheduled date of execution will likely recur in the future, we reach the merits of Singleton’s claims under this exception to the mootness doctrine.
A.
The State urges us to affirm the district court on the ground that 28 U.S.C. § 2244 bars Singleton’s assertion of a Ford or Ford-derivative claim. Conceding that his claim would be barred if brought under § 2254, Singleton argues that his claim is properly before the court under authority of § 2241. We recently considered the application of § 2244’s restrictions on successive habeas applications to a state prisoner’s application brought under § 2241. Crouch v. Norris, 251 F.3d 720 (8th Cir.2001). Crouch applied to this court for permission to file a second habeas petition, claiming that the state had violated his due process rights by refusing to grant him parole. Id. at 722. Crouch argued that because he was not challenging the validity of his conviction or sentence but only the manner in which it was carried out, his claim was properly brought under § 2241 and was not subject to the restrictions in § 2244. Id. at 722-23. We considered several cases which held that a federal prisoner may challenge the manner of execution of his sentence by bringing his petition under § 2241 rather than § 2255. Id. at 722-23. Section 2255, governing federal prisoners, contains narrower language *1023than that in § 2254, which governs state prisoners. The focus of § 2254 is on the petitioner’s custody, not, as in § 2255, on flaws in the underlying judgment or sentence. Id. at 723. Thus, § 2254 is the only means by which “a person in custody pursuant to the judgment of a State court” may raise challenges to the validity of his conviction or sentence or to the execution of his sentence. Id.
That Singleton’s present petition is subject to § 2244 limitations on “second or successive” petitions does not end our inquiry. Section 2244 requires dismissal of a second or successive petition unless the claim raised asserts a new rule of constitutional law or raises new facts that establish the petitioner’s innocence of the underlying offense. As Singleton concedes, he satisfies neither exception.
The threshold determination in a § 2244 inquiry is whether or not the petition is a “second or successive” application. As we discussed at some length in Crouch, whether a later petition is considered “successive” is guided by abuse of the writ principles. 251 F.3d at 723-24 (collecting cases). A claim raised in a prior petition that was dismissed as unripe is not barred by § 2244(b). Stewart v. Martinez-Villareal, 523 U.S. 637, 643-45, 118 S.Ct. 1618, 140 L.Ed.2d 849 (1998). Similarly, a habe-as petition raising a claim that had not arisen at the time of a previous petition is not barred by § 2244(b) or as an abuse of the writ. In re Cain, 137 F.3d 234, 236-37 (5th Cir.1998). We conclude that Singleton’s petition is not “second or successive” because his claim did not arise until he was subject to both a Harper involuntary medication order and a scheduled date of execution. In 1995 Singleton was not under an involuntary medication order. Thus the claim he presents in this appeal could not have been raised prior to the issuance of the 1997 Harper order and is not barred.
B.
We turn now to consider the interrelated issues of whether the State may forcibly administer antipsychotic medication to a prisoner whose date of execution has been set and whether the State may execute a prisoner who has been involuntarily medicated under a Harper procedure. Singleton argues that the involuntary medication regime, legal under Harper during a stay of execution, becomes illegal once an execution date is set because it is no longer in his best medical interest. This issue is one of first impression for this court and is a question of law we review de novo. Hall v. Luebbers, 296 F.3d 685, 692 (8th Cir.2002) (standard of review).
We are guided in our inquiry by Ford v. Wainwright and Washington v. Harper. In Ford, the Supreme Court addressed for the first time the limits imposed by the Eighth Amendment on a State’s power to execute an insane prisoner. Reviewing the common law at the time the Bill of Rights was enacted, the Court found a clear rule against executing the insane despite divergent rationales for such a rule, including the inhumanity and the lack of deterrent and retributive value of such an act. Ford, 477 U.S. at 407-08, 106 S.Ct. 2595. In a concurring opinion, Justice Powell set out the governing standard for determining whether a prisoner is competent to be executed: “[T]he Eighth Amendment forbids the execution only of those who are unaware of the punishment they are about to suffer and why they are to suffer it.” Id. at 422, 106 S.Ct. 2595 (Powell, J., concurring).
In Harper, the Court addressed the question of what limit the Fourteenth Amendment Due Process Clause places on the power of a State to treat a mentally ill prisoner with antipsychotic drugs against his will. Harper, a state prisoner and diagnosed schizophrenic, refused to contin*1024ue taking antipsychotic medication. 494 U.S. at 214, 110 S.Ct. 1028. After receiving medication against his will, Harper challenged as insufficient the procedural protections prisoners were afforded before being forcibly medicated. Id. at 217-18, 110 S.Ct. 1028. Noting that “procedural protections must be examined in terms of the substantive rights at stake,” the Court analyzed the underlying substantive issue of what factual predicate is required before a State may forcibly administer anti-psychotic drugs to a prisoner. Id. at 220, 110 S.Ct. 1028. The Court held that a State may forcibly administer antipsychotic drugs to “a prison inmate who has a serious mental illness ... if the inmate is dangerous to himself or others and the treatment is in the inmate’s medical interest.” Id. at 227,110 S.Ct. 1028.
The limit of a State’s authority to medicate a prisoner involuntarily has been developed further in the context of maintaining or restoring a defendant’s competence to stand trial. In Riggins v. Nevada, the Court decided whether a defendant who was forcibly medicated with antipsychotic drugs to ensure his competence had been denied his right to a fair trial. 504 U.S. 127, 112 S.Ct. 1810, 118 L.Ed.2d 479 (1992). Citing Harper, the Court found that the “substantial interference with [the prisoner’s] liberty” was particularly severe due to the side effects often associated with those drugs. Id. at 184, 112 S.Ct. 1810. Declining to adopt a standard of strict scrutiny, the Court stated that due process required a showing of medical appropriateness and, considering less intrusive alternatives, a showing that treatment is “essential for the sake of [the defendant’s] own safety or the safety of others.” Id. at 135, 112 S.Ct. 1810. Riggins was medicated without “any determination of the need for [the medication] or any findings about reasonable alternatives.” Id. at 136, 112 S.Ct. 1810. The Court held that this was inadequate, considering the “substantial probability of trial prejudice” in the form of the drug’s effect on Riggins’s appearance, testimony, and communication with counsel. Id. at 138, 112 S.Ct. 1810.
We recently considered a due process challenge to forced administration of medication where the state’s sole purpose was to restore a defendant’s competency for trial. United States v. Sell, 282 F.3d 560 (8th Cir.), cert. granted, — U.S.-, 123 S.Ct. 512, 154 L.Ed.2d 394 (2002). In Sell, we held that the government had an “essential interest” in bringing Sell to trial that outweighed his liberty interest in refusing medication. Id. at 568. To justify forcibly medicating an individual to restore competency for trial, the government must (1) “present an essential state interest that outweighs the individual’s interest in remaining free from medication,” (2) “prove that there is no less intrusive way of fulfilling its essential interest,” and (3) “prove by clear and convincing evidence that the medication is medically appropriate.” Id. at 567 (citing Riggins, 504 U.S. at 135, 112 S.Ct. 1810). “Medication is medically appropriate if: (1) it is likely to render the patient competent; (2) the likelihood and gravity of side effects do not overwhelm its benefits; and, (3) it is in the best medical interests of the patient.” Id. (citing United States v. Weston, 255 F.3d 873 (D.C.Cir.2001), and Harper, 494 U.S. at 227, 110 S.Ct. 1028). Where the charges against the defendant are serious, the government’s essential interest in bringing a defendant to trial outweighs his significant liberty interest in avoiding unwanted medication. Id. at 568.
We acknowledge, of course, Sell’s reservation of the question presented by Singleton’s appeal (“[A]n entirely different case is presented when the government wishes to medicate a prisoner in order to render him competent for execution.”) and its admonishment that “our holding must be *1025read narrowly.” Id. at 571 (citations omitted). Notwithstanding Sell’s cautionary comments, we believe that the standards set forth above are applicable to the district court’s rulings in Singleton’s case.
That the government has an essential interest in carrying out a lawfully imposed sentence cannot be doubted. Moran v. Burbine, 475 U.S. 412, 426, 106 S.Ct. 1135, 89 L.Ed.2d 410 (1986) (recognizing “society’s compelling interest in finding, convicting, and punishing those who violate the law”). We need not decide under what circumstances carrying out a particular sentence is not “essential.” Society’s interest in punishing offenders is at its greatest in the narrow class of capital murder cases in which aggravating factors justify imposition of the death penalty. This societal interest must be weighed against Singleton’s interest in being free of unwanted antipsychotic medication. The record before us indicates that Singleton prefers to take the medication rather than be in an unmedicated and psychotic state.3 In addition, Singleton has suffered no substantial side effects. On these facts, the State’s interest in carrying out its lawfully imposed sentence is the superior one.
Singleton has suggested no less intrusive means of ensuring his competence short of antipsychotic medication. The Eighth Amendment forbids the execution of an incompetent person, Ford, 477 U.S. at 401, 106 S.Ct. 2595, thus the State may achieve its essential interest in carrying out Singleton’s sentence of execution only if Singleton is competent. In our order of limited remand, we did not ask the district court to make a finding as to Singleton’s present competence. Other than his “artificial competence” theory, Singleton has never argued, and in fact has agreed repeatedly, that he is competent while he is medicated. In its report, the district court concluded that without medication Singleton would revert to a delusional psychotic state, but it is uncertain whether he would also become Ford-incompetent. On this record, treatment with antipsychotic drugs is necessary to alleviate Singleton’s psychosis, and there is no less intrusive medical treatment by which the government can ensure Singleton’s competence.
Finally, we reach the core of the dispute: whether the antipsychotic medication is medically appropriate for Singleton’s treatment. We review the district court’s findings of fact under the clearly erroneous standard. Sell, 282 F.3d at 568. The first two determinations in the Sell analysis of medical appropriateness are not in serious dispute: first, whether the medication is likely to restore competence, *1026and second whether the expected side effects overwhelm the benefits. The district court found that Singleton was Ford-incompetent at the time the mandatory medication was started in 1997. Singleton’s symptoms have been kept almost completely under control since the initiation of the mandatory medication regime in 1997, and he has repeatedly conceded his competence while medicated. In its denial of Singleton’s petition for habeas corpus, the district court found the record devoid of any significant negative side effects from the antipsychotic medication. These findings are not clearly erroneous, and they establish both that the medication is effective and that the expected side effects do not overwhelm the benefits of the medicine.
Central to Singleton’s argument is his contention that medication “obviously is not in the prisoner’s ultimate best medical interest” where one effect of the medication is rendering the patient competent for execution. Singleton does not dispute that the antipsychotic medication is in his medical interest during the pendency of a stay of execution. He has stated he takes it voluntarily because he does not like the symptoms he experiences without it. He also does not dispute the lack of serious side effects. The factor that Singleton contends takes him outside the scope of Harper is not the existence of serious harmful side effects or an insufficient medical need, but the very psychosis-reducing effect of the medicine. By focusing on his “ultimate best medical interest,” Singleton presents the court with a choice between involuntary medication followed by execution and no medication followed by psychosis and imprisonment. Faced with these two unpleasant alternatives, he offers a third solution: a stay of execution until involuntary medication is no longer needed to maintain his competence.
By focusing on his long-term medical interest, Singleton implicitly concedes that the medication is in his short-term medical interest. Several doctors, both during the Harper determination and at other times, have found the medication to be effective in controlling Singleton’s psychotic symptoms. Singleton’s argument regarding his long-term medical interest boils down to an assertion that execution is not in his medical interest. Eligibility for execution is the only unwanted consequence of the medication. The due process interests in life and liberty that Singleton asserts have been foreclosed by the lawfully imposed sentence of execution and the Harper procedure. In the circumstances presented in this case, the best medical interests of the prisoner must be determined without regard to whether there is a pending date of execution. Thus we hold that the mandatory medication regime, valid under the pendency of a stay of execution, does not become unconstitutional under Harper when an execution date is set.
Closely related to his due process argument, Singleton also claims that the Eighth Amendment forbids the execution of a prisoner who is “artificially competent.” Singleton relies principally on a case construing an analogous provision in the Louisiana Constitution. State v. Perry, 610 So.2d 746 (La.1992). The Perry court, noting that the Louisiana provision is an expansion on the protections of the Eighth Amendment, concluded that the execution of an insane inmate who had been forcibly medicated into competence would violate the state constitution. Id. at 765-66. State courts of last resort may interpret their state constitutions as they see fit. We note, however, that the Perry court accepted the view of “best medical interests” that we have rejected, Id. at 766. The court also found Perry’s medication *1027was ordered solely for purposes of punishment and not for legitimate reasons of prison security or medical need. Id. at 757. We decline to undertake a difficult and unnecessary inquiry into the State’s motives in circumstance where it has a duty to provide medical care. DeShaney v. Winnebago County Dep’t of Soc. Servs., 489 U.S. 189, 199-200, 109 S.Ct. 998, 103 L.Ed.2d 249 (1989); Estelle v. Gamble, 429 U.S. 97, 103, 97 S.Ct. 285, 50 L.Ed.2d 251 (1976) (“These elementary principles establish the government’s obligation to provide medical care for those whom it is punishing by incarceration.”). The findings below support a conclusion that the state was under an obligation to administer antipsychotic medication, thus any additional motive or effect is irrelevant. Ford prohibits only the execution of a prisoner who is unaware of the punishment he is about to receive and why he is to receive it. A State does not violate the Eighth Amendment as interpreted by Ford when it executes a prisoner who became incompetent during his long stay on death row but who subsequently regained competency through appropriate medical care.
We affirm the order of the district court denying Singleton’s petition for writ of ha-beas corpus and vacate the stay of execution.
. The Honorable Garnett Thomas Eisele, United States District Judge for the Eastern District of Arkansas.
. During the hearing conducted pursuant to our order of limited remand, Singleton stated several times that he desires to take the anti-psychotic medication. The transcript further indicates Singleton's attempts to avoid the penalty Arkansas has imposed on him. Dr. Kenneth D. Wright’s notes of his interview with Singleton on March 27, 2000, read in part:
I advised Mr. Singleton that he was taking the medication in shot form that was a tranquilizer and frequently had a side effect of being sedating. I advised him to consider changing the medication to pill form. Mr. Singleton indicated that he could not do this. His exact words were as follows, "I don’t want it to seem like I’m running a game, but I have a case going involving forced medication.”
At this point, I interrupted Mr. Singleton and advised him that several months ago I had elected not to return him to the Forced Medication Review Panel because he appeared to be in remission from psychotic symptoms and he had been taking his medication voluntarily. Mr Singleton, at this point, became enraged, indicating that I did not have the authority to change his medication from being forced.
Mr. Singleton stormed out of the interview ....
Apr. 18, 2000, Hr’g Joint Ex. 2.