The State of Arkansas moves to vacate stays of execution of nine sentences of death entered by the district court on Saturday, April 15, 2017. The first execution is scheduled for today, April 17, at 7:00 p.m. The State moved to vacate the stays at approximately 6:00 p.m. on April 15. The prisoners responded at 1:16 a.m. today, April 17. The State filed a reply at 10:04 a.m. today. Due to the exigency of time, we dispense with a lengthy statement of procedural history and state our conclusions concisely. The judges in regular active service voted to hear the motion initially en banc.
The stays of execution were entered in an action brought by nine Arkansas prisoners under 42 U.S.C. § 1983. The inmates were all convicted of murder and sentenced to death. Governor Hutchinson of Arkansas scheduled executions for eight of the prisoners to occur on April 17, 20, 24, and 27, 2017, two per day. As relevant here, the complaint alleges that use of the State’s method of execution, by itself and in combination with the execution schedule, would constitute cruel and unusual punishment that violates the Eighth and Fourteenth Amendments. The State’s current lethal injection protocol calls for injection of 500 milligrams of midazolam, followed by 100 milligrams of vecuronium bromide, followed by 240 milliequivalents of potassium chloride. If the prisoner remains conscious after the injection of mi-dazolam, however, the executioner will inject another 500 milligrams of midazolam before injecting vecuronium bromide.
*491The district court based its order staying the executions on three principal conclusions: (1) the inmates did not delay unnecessarily in bringing this action, (2) “there is a significant possibility that plaintiffs will succeed in showing that the use of midazolam in the ADC’s current lethal injection protocol qualifies as an objectively intolerable risk that plaintiffs will suffer severe pain,” and (3) there is a significant possibility that the risk of severe pain arising from Arkansas’s proposed method of execution is substantial when compared to known and available alternative methods. The district court conducted a four-day hearing and produced a 101-page order under great time pressure, and we commend the court for its diligence. For the following reasons, however, we conclude that the district court abused its discretion in staying the executions, and we therefore grant the State’s motion to vacate the stays.
First, “[a] court considering a stay must ... apply ‘a strong equitable presumption against the grant of a stay where a claim could have been brought at such a time as to allow consideration of the merits without requiring entry of a stay.’ ” Hill v. McDonough, 547 U.S. 573, 584, 126 S.Ct. 2096, 165 L.Ed.2d 44 (2006) (quoting Nelson v. Campbell, 541 U.S. 637, 650, 124 S.Ct. 2117, 158 L.Ed.2d 924 (2004)). The record here shows that the prisoners could have brought their § 1983 method-of-execution claim much earlier and intentionally declined to do so.
The Arkansas legislature adopted the current method of execution in 2015. On April 6, 2015, several of the prisoners sued in Arkansas state court to challenge the constitutionality of the law under both the Arkansas Constitution and the federal Constitution. After the State removed the case to federal court, however, the prisoners voluntarily dismissed the case without prejudice on April 18, 2015. They then filed a new action in Arkansas state court that omitted the federal claims and alleged only violations of Arkansas law. After more than a year of litigation, the Arkansas Supreme Court — applying the same standards that apply under the Eighth Amendment of the federal Constitution— dismissed the prisoners’ claim that the method of execution constituted cruel or unusual punishment in violation of the Arkansas Constitution. Kelley v. Johnson, 2016 Ark. 268, 496 S.W.3d 346, 357-60 (2016), cert. denied, — U.S. -, 137 S.Ct. 1067, 197 L.Ed.2d 235 (2017).
On February 27, 2017, six days after the Supreme Court denied certiorari in Kelley, the Governor scheduled executions for eight of the inmates to occur in April 2017. Finally, on March 27, 2017, only three weeks before the first scheduled execution, the plaintiffs brought this action to challenge the method of execution under the Eighth Amendment of the federal Constitution.
The prisoners’ long delay in pursuing their federal claim should have created.a strong equitable presumption against the grant of a stay. The prisoners voluntarily elected to forego their federal claim in April 2015 and chose instead to challenge the method of execution exclusively in state court under the Arkansas Constitution. Only after the Arkansas Supreme Court rejected their state-law claim, the Supreme Court denied certiorari, and the Governor scheduled the executions did the prisoners present a federal claim in federal court. The claim on which the district court based the stays of execution — that the three-drug lethal injection protocol allegedly violates the Eighth Amendment— could have been litigated at the same time as the state constitutional claim beginning in April 2015. Whether or not the claim technically is barred by doctrine of res *492judicata or collateral estoppel, the prisoners’ use of “piecemeal litigation” and dilatory tactics is sufficient reason by itself to deny a stay. Hill, 547 U.S. at 584-85, 126 S.Ct. 2096.
Although the district court said that a risk of pain arising from the lethal-injection protocol is “exacerbated” by the Governor’s execution schedule, R. Doc. 54, at 56, the court did not explain why. The alleged risk of pain from the drug protocol is the central basis for the district court’s order granting stays. The prisoners could have challenged the protocol beginning in April 2015. We are not convinced that the execution schedule is material to the question whether stays are warranted based on the lethal-injection protocol.
Second, the district court’s conclusion concerning the use of midazolam in the Arkansas execution protocol did not apply the governing standard and was not adequately supported by the court’s factual findings. To establish a violation of the Eighth Amendment, prisoners must show that the method of execution is “sure or very likely to cause serious illness and needless suffering.” Glossip v. Gross, — U.S. -, 135 S.Ct. 2726, 2737, 192 L.Ed.2d 761 (2015) (quoting Baze v. Rees, 553 U.S. 35, 50, 128 S.Ct. 1520, 170 L.Ed.2d 420 (2008) (plurality opinion)). While the district court found a significant possibility that the prisoners could show an “objectively intolerable risk” of severe pain, the court never found that the prisoners had a likelihood of success under the rigorous “sure or very likely” standard of Glossip and Baze. Although the court recited the “sure or very likely” standard in its preliminary discussion, R. Doc. 54, at 55, the court never applied it when discussing whether stays of execution were justified.
The district court’s factual findings would not support a conclusion that the prisoners have a likelihood of success in showing that the execution protocol is sure or very likely to cause severe pain. Much of the district court’s order highlights the equivocal nature of the evidence. The court observed that there are no scientific studies conducted in humans about the effects of the dosage of midazolam that would be administered under the protocol. One human study involving smaller doses was “mixed in terms of supporting either side’s theory.” R. Doc. 54, at 58. The court discussed the alleged “ceiling effect” for mi-dazolam, under which effectiveness levels off at a certain dosage, but concluded that if there is a ceiling effect, the level is unknown. Id. at 60. Evidence from executions in other jurisdictions was of “limited relevance.” Id. at 69; see In re Ohio Execution Protocol, No. 17-3076, — F.3d -, -, 2017 WL 1457946, at *22 (6th Cir. Apr. 25, 2017) (Kethledge, J., dissenting). There is no express finding of fact that the prisoners are likely to prove that a 500-milligram injection of midazolam will fail to anesthetize the prisoners during the execution or that use of the lethal-injection protocol is sure or very likely to cause severe pain. Instead, the district court found that “there appears at least a possibility that if the midazolam does not operate as defendants predict ..., the inmate may regain some level of consciousness during the process before the second and third drugs are administered.” R. Doc. 54, at 72-73.
The district court appeared to acknowledge that there was no “well-established scientific consensus” that the use of mi-dazolam in conjunction with the other two drugs was very likely to cause severe pain. Id. at 68-69. But the district court thought this standard — urged by Justice Alito in Baze to avoid “embroiling] the States in never-ending litigation concerning the adequacy of their execution procedures,” 553 *493U.S. at 63, 67, 128 S.Ct. 1520 (Alito, J., concurring) — “seems like a high bar to reach and level of certainty to achieve based on the evidence of which the Court is aware at this stage of the proceeding and the limitations of human study at 500 mg, 1,000 mg, or higher doses of midazo-lam.” R. Doc. 54, at 69.
“When a method of execution is authorized under state law, a party contending that this method violates the Eighth Amendment bears the burden of showing that the method creates an unacceptable risk of pain.” Glossip, 135 S.Ct. at 2741. If there is no scientific consensus and a paucity of reliable scientific evidence concerning the effect of a lethal-injection protocol on humans, then the challenger might well be unable to meet this burden. The equivocal evidence recited by the district court falls short of demonstrating a significant possibility that the prisoners will show that the Arkansas protocol is “sure or very likely” to cause severe pain and needless suffering.
Third, we disagree with the legal standard that the district court applied in determining whether alternative methods of execution are known and available. We do not say that an alternative method must be authorized by statute or ready to use immediately, but we concur with the Eleventh Circuit that the State must have access to the alternative and be able to carry out the alternative method relatively easily and reasonably quickly. Arthur v. Comm’r, Ala. Dep’t of Corr., 840 F.3d 1268, 1300 (11th Cir. 2016), cert. denied, — U.S. -, 137 S.Ct. 725, 197 L.Ed.2d 225 (2017).
The district court thought this standard places an “impossible burden” on the prisoners. We think it is necessary to conform to the Eighth Amendment. Unless an alternative is feasible and readily implemented in the sense described, the State has a legitimate penological justification for adhering to its current method of execution in order to carry out lawful sentences. See Baze, 553 U.S. at 52, 128 S.Ct. 1520 (plurality opinion). When availability (or effectiveness) of an alternative is more speculative, a State’s refusal to discontinue executions under the current method is not blameworthy in a constitutional sense. See Baze, 553 U.S. at 67, 128 S.Ct. 1520 (Alito, J., concurring). The “reasonable possibility” standard urged by the prisoners based on In re Ohio Execution Protocol, — F.3d at -, 2017 WL 1457946, at *9, is insufficient to establish that an alternative method is available, feasible, and readily implemented. See id. at - - -, 2017 WL 1457946, at *23-24 (Kethledge, J., dissenting).
Under our view of the correct legal standard, we cannot agree with the district court that the prisoners have demonstrated a significant possibility of establishing a known and available alternative that would significantly reduce a substantial risk of severe pain. Even assuming a risk of pain from the current method, the availability of the several methods cited by the district court is too uncertain to satisfy the rigorous standard under the Eighth Amendment.
The possibility that Arkansas could acquire pentobarbital for use in executions is too speculative to justify stays of execution. Arkansas made at least three unsuccessful inquiries about obtaining barbiturates in 2015, and the difficulty of obtaining drugs for use in lethal injection is well documented. Sevoflurane gas and nitrogen hypoxia have never been used to carry out an execution. With no track record of successful use, these methods are not likely to emerge as more than a “slightly or marginally safer alternative.” Glossip, 135 S.Ct. at 2737; see Baze, 553 *494U.S. at 41, 128 S.Ct. 1520 (discussing “untried and untested alternatives”). The firing squad has been used by only one State since the 1920s. It requires trained marksmen who are willing to participate and is allegedly painless only if volleys are targeted precisely. The record comes short of establishing a significant possibility that use of a firing squad is readily implemented and would significantly reduce a substantial risk of severe pain.
For these reasons, the stays of execution entered on April 15, 2017, R. Doc. 54, are vacated.