In the case of Michael Wayne Williams v. John Taylor, Warden (1999), the Supreme Court ruled in favor of Williams, a death row inmate who had been convicted for murder and robbery. The court found that his Sixth Amendment rights were violated because he was not allowed to present mitigating evidence during his sentencing hearing. This evidence included details about his troubled upbringing and mental health issues which could have potentially influenced the jury's decision on whether or not to impose capital punishment. The Court held that this denial constituted an unconstitutional limitation on his right to defend himself against a death sentence, thus violating due process under both Kentucky law and federal constitutional standards.

In the dissenting opinion for Michael Wayne Williams v. John Taylor, Warden, Justice Scalia disagreed with the majority's decision to grant habeas corpus relief to Williams based on ineffective assistance of counsel during sentencing. He argued that there was no constitutional right to effective assistance of counsel at sentencing and therefore, it could not be a basis for granting habeas corpus relief. Furthermore, he contended that even if such a right existed, Williams had failed to demonstrate prejudice as required by Strickland v. Washington because there was no reasonable probability that but for his attorney's alleged errors in failing to present mitigating evidence about his background and mental health issues during sentencing phase would have resulted in different outcome given the severity of his crimes which included multiple murders.