Breyer, J., dissenting
study of euthanasia in horses. Ante, at 26–27. Bucklew’s expert, however, did not rely exclusively or even heavily upon that study; he mentioned it only in response to a question posed in his deposition. To the contrary, Dr. Zivot explained that his testimony regarding the pain to which Bucklew would be subjected was “supported both by [his] own professional knowledge of how chemicals of this type are likely to exert their effects in the body as well as by the terms of Missouri’s Execution Procedure.” App. 222.
Whether any mistake about the importance of a single study makes all the difference to Bucklew’s case is a matter not for this Court to decide at summary judgment, but for the factfinder to resolve at trial. As Judge Colloton pointed out in dissent below, attacks on the “reliability and credibility of Dr. Zivot’s opinion,” including “his possible misreading of the horse study on which he partially relied,” give rise to factual disputes. See 883 F. 3d 1087, 1099 (CA8 2018). Judge Colloton therefore concluded that “[t]he district court did not err in concluding that it could not resolve the dispute between the experts on summary judgment.” Ibid. I agree.
II
This case next presents a legal question. The Court in Glossip held in the context of a facial challenge to a State’s execution protocol that the plaintiffs were required not only to establish that the execution method gave rise to a “demonstrated risk of severe pain,” but also to identify a “known and available” alternative method. 576 U. S., at ___ (slip op., at 13). The Court added that the alternative must be “feasible, readily implemented, and in fact significantly reduc[e] a substantial risk of severe pain.” Id., at ___–___ (slip op., at 12–13) (internal quotation marks omitted).
I joined the dissent in Glossip, but for present purposes
