In the case of James Walker, Warden et al., v. Charles W. Martin in 2010, the U.S Supreme Court ruled on a habeas corpus petition by an inmate who claimed his state court conviction was unconstitutional due to ineffective counsel. The Ninth Circuit granted relief but the Supreme Court reversed this decision stating that federal courts must defer to last reasoned state-court decisions when reviewing habeas petitions under Antiterrorism and Effective Death Penalty Act (AEDPA). In this case, California's informal system for reviewing denial of parole did not meet AEDPA’s requirements for deferring to a state court's legal conclusions because it lacked reasoning behind its decision-making process. Therefore, federal courts were free to review Martin’s claim de novo or anew without any deference given towards previous rulings made by lower courts.

In the dissenting opinion for the case of James Walker, Warden, et al., v. Charles W. Martin, Justice Scalia disagreed with the majority's decision to grant habeas relief to Martin based on a perceived error in jury instructions during his trial. He argued that there was no established Supreme Court precedent at the time of Martin’s state-court adjudication that clearly stated he had a right to have jurors instructed about how they could consider mitigating evidence in capital cases. Furthermore, Scalia contended that even if such an instruction were constitutionally required and its absence constituted an unreasonable application of federal law as determined by SCOTUS (Supreme Court Of The United States), any potential error would be harmless given overwhelming evidence supporting death penalty verdicts in similar cases.