In the 1995 case of Carl Thompson v. Patrick Keohane, Warden et al., the U.S Supreme Court addressed a habeas corpus petition from an inmate who claimed his constitutional rights were violated during his trial. Thompson was convicted for murder and sentenced to death in Kentucky state court. He argued that he received ineffective assistance of counsel because his attorney failed to present mitigating evidence about his background and mental health during the penalty phase of his trial, which could have potentially spared him from a death sentence. The District Court denied relief but on appeal, the Sixth Circuit reversed this decision stating that there was reasonable probability that outcome would have been different had such evidence been presented at sentencing stage. However, upon further review by Supreme Court it held that federal courts should not grant habeas relief based solely on speculation about what might have occurred if certain evidence had been introduced at sentencing; rather they must find "a substantial or injurious effect" on jury's verdict.

In the dissenting opinion for Carl Thompson v. Patrick Keohane, Warden et al., Justice Ginsburg argued that the majority's decision was inconsistent with previous rulings of the Court and failed to respect principles of federalism. She contended that a state prisoner should be allowed to challenge his conviction in federal court on grounds not raised in state court if he can show cause for failing to raise them earlier and actual prejudice resulting from the errors. In this case, she believed Thompson had shown both cause and prejudice: his trial counsel’s failure to object constituted ineffective assistance, satisfying “cause,” while evidence against him was far from overwhelming, indicating “prejudice.” Furthermore, she criticized the majority's reliance on procedural default rules which were inconsistently applied by Michigan courts at best. This inconsistency made it unfair to penalize Thompson for failing to comply with these rules when it wasn't clear they would have been enforced against him.