In the case of In re Spencer in 1969, the United States Supreme Court dealt with a habeas corpus petition. The petitioner, Spencer, was convicted for burglary and sentenced to life imprisonment under California's recidivist statute due to his previous convictions. He challenged his conviction on grounds that he had been denied effective assistance of counsel because his lawyer did not object to evidence obtained through an allegedly illegal search and seizure. However, the court dismissed this claim stating that even if there were any constitutional errors during trial proceedings they would be considered harmless beyond reasonable doubt as long as they didn't contribute to the conviction verdict. Furthermore, it was found that there wasn’t enough proof showing ineffective legal representation by defense counsel or prejudice against him resulting from alleged unlawful search and seizure.

In the dissenting opinion for In re Spencer, it was argued that the majority's decision to deny habeas corpus relief to state prisoners who had already served their sentences but were still under parole supervision was flawed. The dissenting justices believed this interpretation of "custody" in federal habeas statutes as not including parolees was too narrow and inconsistent with previous rulings. They contended that a person on parole is significantly restrained by conditions of his release and thus should be considered 'in custody' for purposes of federal habeas review. Furthermore, they expressed concern about potential injustices if such individuals are denied access to federal courts because they have technically completed their prison terms despite remaining under state control through parole restrictions.