Abel Hidalgo was sentenced to death for two counts of first degree murder in 2015. He appealed to the Supreme Court of Arizona, which upheld [opinion] the death sentence and found that the trial court properly denied Hidalgo's motion alleging the unconstitutionality of Arizona's death penalty statute without first holding an evidentiary hearing on the matter. At the end of 2017, Hidalgo appealed to the US Supreme Court asking the court to decide whether Arizona's death penalty statute is constitutional since it allows almost all those convicted of first-degree murder to be eligible and whether the death penalty in general violates the Eighth Amendment.
In a statement respecting the denial of certiorari, Justice Stephen Breyer explained that the court declined to hear the case because there was not enough evidence in Hidalgo's submission since the evidentiary hearing was denied. The court also decided that it had not been adequately explained whether an empirical study would have been relevant or helpful to resolving the question of the constitutionality of the death penalty. In the closing paragraph Bryer wrote, "Capital defendants may have the opportunity to fully develop a record with the kind of empirical evidence that the petitioner points to here. And the issue presented in this petition will be better suited for certiorari with such a record."