In the 1940 case Walker v. Johnston, the U.S. Supreme Court ruled in favor of a prisoner who had filed a habeas corpus petition challenging his conviction on grounds that he was denied effective assistance of counsel during his trial. The petitioner, Walker, argued that he was not given adequate time to consult with his attorney before being asked to plead guilty and did not fully understand the implications of pleading guilty due to lack of proper legal advice from an attorney who only met him briefly prior to court proceedings. The Supreme Court agreed with Walker's argument and held that such circumstances violated his constitutional right under the Sixth Amendment for effective assistance of counsel during criminal prosecutions. This ruling established important precedent regarding defendants' rights for competent legal representation in criminal cases.

In the dissenting opinion for Walker v. Johnston, Justice Frank Murphy argued that the majority's decision to deny habeas corpus relief was too restrictive and failed to consider important factors in the case. He believed that a prisoner should have access to this form of relief if they can demonstrate a reasonable doubt about their guilt or innocence due to new evidence or constitutional violations during their trial. In this particular case, he felt there were significant questions regarding whether Walker had received effective legal representation at his original trial, which could potentially undermine his conviction. Therefore, he disagreed with the majority's ruling and would have granted Walker's petition for habeas corpus.