Hidalgo v. Arizona, 138 S.Ct. 1054

Petitioner Abel Daniel Hidalgo, convicted of first-degree murder in Arizona, challenged the State’s capital sentencing scheme under the Eighth Amendment, arguing Arizona’s statutory aggravators make virtually every first-degree murder death-eligible.
Arizona defines first-degree murder broadly (premeditated and felony murder based on 22 predicate felonies) and does not rely solely on a narrow capital-offense definition to restrict death eligibility.
Arizona instead lists statutory aggravating circumstances (14 at present) that must be found at sentencing; at least one aggravator is required for a death sentence.
Hidalgo presented empirical evidence from Maricopa County (2002–2012) showing aggravators were present in 856 of 866 first-degree murder cases (~98%), and sought an evidentiary hearing to develop the record; the trial court denied the hearing and the Arizona Supreme Court assumed the data was correct but upheld the scheme.
Justice Breyer (joined by Justices Ginsburg, Sotomayor, and Kagan) filed a statement respecting denial of certiorari: he agreed to deny certiorari but explained the Court’s narrowing precedents and noted the state courts below misapplied them; he emphasized the record was underdeveloped and that a fully developed empirical record would better present the constitutional question.

Issue	Plaintiff's Argument	Defendant's Argument	Held
Whether Arizona’s capital scheme genuinely narrows the class of persons eligible for death	Hidalgo: Arizona’s statutory aggravators apply to nearly all first-degree murders (~98%), so the scheme fails the Eighth Amendment narrowing requirement	Arizona: Narrowing is achieved through multiple mechanisms (aggravators, proof beyond a reasonable doubt, appellate review, individualized sentencing), and prosecutors can limit death requests	Court denied certiorari; Breyer statement said Arizona Supreme Court misapplied precedent but record is undeveloped, so certiorari inappropriate now

Tuilaepa v. California, 512 U.S. 967 (jurisprudence distinguishes eligibility and selection stages in capital sentencing)
Lowenfield v. Phelps, 484 U.S. 231 (legislature may narrow by statute or by listing aggravating circumstances for jury finding)
Zant v. Stephens, 462 U.S. 862 (statutory aggravators perform constitutionally necessary legislative narrowing)
Kansas v. Marsh, 548 U.S. 163 (summary of eligibility and selection requirements under Eighth Amendment)
Furman v. Georgia, 408 U.S. 238 (per curiam) (capital punishment Eighth Amendment principles)
Gregg v. Georgia, 428 U.S. 153 (established constitutional frameworks for guided capital sentencing)
California v. Ramos, 463 U.S. 992 (discussion of legislature-defined categories vs. sentencing consideration)
Jurek v. Texas, 428 U.S. 262 (upholding narrowly defined capital murder statute)
Brown v. Sanders, 546 U.S. 212 (statutory factors determine death eligibility)