McKinney v. Arizona

James McKinney was sentenced to death for a 1991 double murder in Arizona. After his original sentence was overturned due to an Eddings error, an Arizona trial judge resentenced him to death. McKinney argued on federal habeas review that the resentencing failed to properly consider his traumatic childhood and mental health as mitigating evidence. The Ninth Circuit agreed and granted relief. The U.S. Supreme Court reversed in a 5-4 decision, holding that the Ninth Circuit did not apply the required AEDPA deference to the state court’s determination. The Court ruled the state court’s conclusion—that the mitigating evidence lacked a causal connection to the crime—was not an unreasonable application of clearly established federal law.

The U.S. Supreme Court reversed the Ninth Circuit’s judgment, holding that the state court’s decision was not contrary to or an unreasonable application of federal law. McKinney’s death sentence was reinstated.

Whether the Arizona state court unreasonably applied clearly established federal law, specifically the rule from Eddings v. Oklahoma, by failing to give sufficient weight to McKinney’s mitigating evidence of childhood abuse and mental health issues when resentencing him to death.

The ruling reinforced the highly deferential AEDPA standard in capital cases, making it significantly harder for death row inmates to obtain federal habeas relief on claims of improper consideration of mitigating evidence. It affirmed the broad discretion of state courts in weighing aggravating and mitigating factors during resentencing.