In the 1967 case Peyton, Penitentiary Superintendent v. Rowe et al., the U.S. Supreme Court ruled that a prisoner could challenge his state court conviction in federal court before he had finished serving his sentence for another crime. The decision overturned an earlier ruling (McNally v. Hill) which held that a prisoner must first serve out their current sentence before challenging any future sentences on constitutional grounds in federal habeas corpus proceedings. In this case, two Virginia inmates sought to contest their convictions while still serving time for unrelated crimes, arguing they were denied effective counsel and due process rights during trial and sentencing respectively. The Supreme Court sided with them stating that it was unjust to make prisoners wait until they began serving potentially unconstitutional sentences to challenge them.

In the dissenting opinion for Peyton v. Rowe, Justice Harlan argued that the majority's decision to allow federal prisoners to challenge their state convictions while still in custody was a departure from established habeas corpus jurisprudence. He contended that this ruling would lead to an increase in frivolous litigation and place unnecessary burdens on both federal and state courts. Furthermore, he believed it could potentially undermine finality of judgments by allowing convicts multiple opportunities to contest their sentences. Thus, he disagreed with the majority's interpretation of "in custody" under federal law as including future imprisonment under a separate sentence not yet being served.