But it is only noncompliance with federal law that renders a State's criminal judgment susceptible to collateral attack in the federal courts. The habeas statute unambiguously provides that a federal court may issue the writ to a state prisoner "only on the ground that he is in custody in violation of the Constitution or laws or treaties of the United States." And we have repeatedly held that "federal habeas corpus relief does not lie for errors of state law."

In 1997, an Indiana trial court found Corcoran guilty of four counts of murder. The trial judge sentenced him to death, relying on non-statutory aggravating factors. In 2000, the Indiana Supreme Court [official website] vacated the sentence because the trial court may have weighed factors of the innocence of the victims, heinousness of the offense and future dangerousness as aggravating circumstances, and later accepted a revised sentencing order issued in 2002. Corcoran applied for a writ of habeas corpus in the US District Court for the Northern District of Indiana [official website], arguing that the trial court relied on impermissible aggravating factors. In 2007, the district court granted habeas relief on the grounds that the prosecutor violated the Sixth Amendment [text] when offering to take the death penalty off the table in exchange for a waiver of a jury trial. In 2008, the appeals court denied the district court's habeas relief, but later granted the petition on remand from the Supreme Court in 2010, arguing that, in order to comply with Indiana law, the trial court needed to reconsider its sentencing determination.