In the 1991 case of J.C. Keeney, Superintendent, Oregon State Penitentiary v. Jose Tamayo-Reyes, the U.S. Supreme Court ruled on whether a defendant could waive his right to present mitigating evidence in a capital sentencing hearing and then later claim that his attorney was ineffective for honoring this waiver. The court held that when a defendant instructs his counsel not to offer any mitigating evidence at the penalty phase of a capital trial, he cannot later argue that by following these instructions, his counsel's performance fell below an objective standard of reasonableness under Strickland v. Washington (1984). However, if it can be shown that there were significant reasons why counsel should have doubted either client’s capacity or understanding regarding such decision-making process due to mental impairment or language barrier issues; then it may be possible for them to make an ineffectiveness claim based on their lawyer's failure in investigating potential defenses before accepting their instruction against presenting mitigation.

In the case of J. C. Keeney, Superintendent, Oregon State Penitentiary v. Jose Tamayo-Reyes, Justice Scalia delivered a dissenting opinion in which Chief Justice Rehnquist and Justices White and Thomas joined him. The dissent argued that the majority's decision to allow federal habeas courts to review state procedural defaults if a petitioner can show cause for default and actual prejudice was an overreach of their authority as it undermined states' rights to enforce their own procedural rules in criminal cases. They also disagreed with the majority's interpretation of "cause" for default as including ineffective assistance by post-conviction counsel; they believed this expanded the definition too broadly beyond what Congress intended when it enacted 28 U.S.C §2254 (the statute governing federal habeas corpus relief). Furthermore, they contended that allowing such broad exceptions would encourage defendants to strategically withhold claims until federal habeas proceedings.