O’neal v. McAninch

Summary

The Court, in an opinion by Justice Breyer, held that when a federal habeas judge remains in grave doubt whether a constitutional trial error had a substantial and injurious effect or influence on the jury’s verdict, the error must be treated as harmful. Grave doubt means virtual equipoise after conscientious review of the record. The Court relied on harmless-error precedent, the purposes of habeas corpus, and administrative consistency, and found that the habeas statute did not require a contrary result. It vacated the Sixth Circuit’s judgment and remanded. Justice Thomas, joined by Chief Justice Rehnquist and Justice Scalia, dissented, arguing that the habeas petitioner must establish a causal connection between the error and custody and therefore must lose when the judge remains in equipoise.