In the case of Burger v. Kemp, Warden in 1986, the U.S Supreme Court upheld a death sentence for William Neal Moore who was convicted of murder in Georgia. The defense argued that Moore's counsel had been inadequate during his trial and sentencing because they failed to present mitigating evidence about his background and character. However, the court ruled 5-4 that even if this evidence had been presented it would not have changed the outcome of the trial or sentencing due to overwhelming aggravating factors such as prior convictions for violent crimes including rape and armed robbery. Therefore, there was no violation of Moore's Sixth Amendment right to effective assistance of counsel.

In the dissenting opinion for Burger v. Kemp, Justice Brennan, joined by Justices Marshall and Blackmun, argued that the majority's decision to uphold Kemp's death sentence was flawed due to inadequate representation during his trial. They contended that Kemp’s lawyer failed to conduct a thorough investigation into potential mitigating evidence which could have influenced the jury’s decision on sentencing. This included neglecting to present key aspects of Kemp's background such as his troubled childhood and mental health issues. The dissenters believed this constituted ineffective assistance of counsel in violation of Sixth Amendment rights, thus rendering the death penalty verdict unconstitutional under Eighth Amendment protections against cruel and unusual punishment.