In the case of Scott Wayne Blystone v. Pennsylvania, 1989, the U.S. Supreme Court upheld a death sentence for first-degree murder despite arguments that it violated the Eighth Amendment's prohibition against cruel and unusual punishment. The defendant argued that his inability to present mitigating evidence unrelated to his capacity to appreciate criminal conduct or conform his behavior was unconstitutional under Lockett v. Ohio (1978). However, the court ruled in a 5-4 decision that Pennsylvania’s sentencing scheme did not violate this precedent because it allowed defendants to introduce any relevant mitigating evidence during their trial's penalty phase; they were only limited from introducing such evidence when arguing specifically against an aggravating circumstance used by prosecutors seeking capital punishment. Therefore, while Blystone could not use certain types of mitigation as direct counterarguments against specific aggravators, he still had ample opportunity overall to argue for leniency based on other aspects of character or record.

In the dissenting opinion for Scott Wayne Blystone v. Pennsylvania, Justice Brennan, joined by Justices Marshall and Blackmun, argued that the death penalty statute in question was unconstitutional because it did not allow a defendant to present mitigating evidence unless it directly related to one of seven specific factors outlined by the state law. They believed this restriction violated the Eighth Amendment's prohibition against cruel and unusual punishment as interpreted in previous Supreme Court decisions which required that defendants be allowed to introduce any relevant mitigating evidence during sentencing hearings in capital cases. The dissenting justices also disagreed with majority’s interpretation of precedent regarding mandatory death sentences; they asserted that even though juries had discretion over whether certain aggravating circumstances existed beyond reasonable doubt, once these were found, imposition of death sentence became obligatory thus making it effectively a mandatory sentence contrary to prior rulings.