In the case of Dunn v. Reeves, 2020, the United States Supreme Court overturned a decision by the Eleventh Circuit Court that had granted habeas relief to Matthew Reeves, who was convicted for murder and sentenced to death in Alabama. The main issue revolved around whether Mr. Reeves's counsel provided ineffective assistance during his trial by not adequately investigating or presenting evidence related to his mental health as part of an insanity defense strategy. The Supreme Court ruled that even if there were deficiencies in representation, they did not prejudice Mr.Reeves’s case because there was significant evidence supporting his guilt beyond reasonable doubt including eyewitness testimony and physical evidence linking him directly to the crime scene and victim.

In the dissenting opinion for Dunn v. Reeves, Justice Sonia Sotomayor argued that the majority's decision to overturn a lower court ruling granting relief to Matthew Reeves was flawed and unjust. She contended that the Alabama courts had failed in their duty by not properly evaluating whether or not Reeves' lawyer provided effective assistance during his trial. Specifically, she pointed out that his attorney did not investigate or present evidence of serious mental health issues which could have influenced the jury’s sentencing decision. Furthermore, she criticized her colleagues for ignoring established precedent regarding ineffective counsel claims and habeas corpus review standards set forth in previous Supreme Court cases like Strickland v. Washington and Williams v Taylor respectively.