In the 2009 case of Holly Wood v. Richard F. Allen, Commissioner, Alabama Department of Corrections et al., the U.S Supreme Court ruled in favor of petitioner Holly Wood who was convicted for murder and sentenced to death by an Alabama court. The main issue revolved around whether or not his legal counsel provided ineffective assistance during sentencing by failing to present mitigating evidence about his mental capacity. The Supreme Court held that it was unreasonable for the state court to conclude that there had been no deficient performance on part of Wood's attorneys when they failed to investigate and present substantial mitigating evidence regarding his borderline intellectual functioning at sentencing phase. This decision emphasized a defendant's right under Sixth Amendment’s guarantee for effective assistance of counsel which includes thorough investigation into potential mitigation before deciding strategy in capital cases.

In the dissenting opinion for Holly Wood v. Richard F. Allen, Justice John Paul Stevens argued that Wood's counsel was ineffective due to their failure to investigate and present mitigating evidence about his mental condition at sentencing. He contended that this omission could have potentially altered the outcome of the case as it may have led jurors to recommend a life sentence instead of death penalty if they had known about his borderline intellectual functioning and significant cognitive impairments. Furthermore, he criticized the majority's decision stating that it failed to properly apply established legal principles regarding effective assistance of counsel under Strickland v. Washington (1984). According to him, an attorney’s duty is not only limited in presenting mitigation evidence but also includes conducting a thorough investigation into potential mitigating factors which was neglected by Wood’s attorneys.