CERTIORARI TO THE SUPREME COURT OF SOUTH CAROLINA.
White, J., delivered the opinion of the Court, in which Brennan, Marshall, Blackmun, Stevens, and O'connor, JJ., joined. Powell, J., filed an opinion concurring in the judgment, in which Burger, C. J., and Rehnquist, J., joined, post, p. 9.
JUSTICE WHITE delivered the opinion of the Court.
Petitioner Ronald Skipper was convicted in a South Carolina trial court of capital murder and rape. The State sought the death penalty, and a separate sentencing hearing was held before the trial jury under S. C. Code § 16-3-20 (1985), which provides for a bifurcated trial and jury sentencing in capital cases. Following introduction by the State of evidence in aggravation of the offense (principally evidence of petitioner's history of sexually assaultive behavior), petitioner presented as mitigating evidence his own testimony and that of his former wife, his mother, his sister, and his grandmother. This testimony, for the most part, concerned
the difficult circumstances of his upbringing. Petitioner and his former wife, however, both testified briefly that petitioner had conducted himself well during the 7 1/2 months he spent in jail between his arrest and trial. Petitioner also testified that during a prior period of incarceration he had earned the equivalent of a high school diploma and that, if sentenced to life imprisonment rather than to death, he would behave himself in prison and would attempt to work so that he could contribute money to the support of his family.
Petitioner also sought to introduce testimony of two jailers and one "regular visitor" to the jail to the effect that petitioner had "made a good adjustment" during his time spent in jail. The trial court, however, ruled that under the South Carolina Supreme Court's decision in State v. Koon, 278 S. C. 528, 298 S. E. 2d 769 (1982) (Koon I), such evidence would be irrelevant and hence inadmissible. The decision in Koon I, the judge stated, stood for the rule that "whether [petitioner] can adjust or not adjust" was "not an issue in this case." App. 11.
After hearing closing arguments -- during the course of which the prosecutor contended that petitioner would pose disciplinary problems if sentenced to prison and would likely rape other prisoners, id., at 13-14 -- the jury sentenced petitioner to death. On appeal, petitioner contended that the trial court had committed constitutional error in excluding the testimony of the jailers and the visitor: the testimony of these witnesses, petitioner argued, would have constituted relevant mitigating evidence, and exclusion of such evidence was improper under this Court's decisions in Lockett v. Ohio, 438 U.S. 586 (1978), and Eddings v. Oklahoma, 455 U.S. 104 (1982). The Supreme Court of South Carolina rejected petitioner's contention, stating:
"The trial judge properly refused to admit evidence of [petitioner's] future adaptability to prison life. State v. Koon, supra. However, evidence of his past adaptability was admitted through testimony of his former wife,
his mother and his own testimony. This contention is without merit." 285 S. C. 42, 48, 328 S. E. 2d 58, 61-62 (1985).
We granted certiorari, 474 U.S. 900 (1985), to consider petitioner's claim that the South Carolina Supreme Court's decision is inconsistent with this Court's decisions in Lockett and Eddings, and we now reverse.
There is no disputing that this Court's decision in Eddings requires that in capital cases "'the sentencer . . . not be precluded from considering, as a mitigating factor, any aspect of a defendant's character or record and any of the circumstances of the offense that the defendant proffers as a basis for a sentence less than death.'" Eddings, supra, at 110 (quoting Lockett, supra, at 604 (plurality opinion of BURGER, C. J.)) (emphasis in original). Equally clear is the corollary rule that the sentencer may not refuse to consider or be precluded from considering "any relevant mitigating evidence." 455 U.S., at 114. These rules are now well established, and the State does not question them.
Accordingly, the only question before us is whether the exclusion from the sentencing hearing of the testimony petitioner proffered regarding his good behavior during the over seven months he spent in jail awaiting trial deprived petitioner of his right to place before the sentencer relevant evidence in mitigation of punishment. It can hardly be disputed that it did. The State does not contest that the witnesses petitioner attempted to place on the stand would have testified that petitioner had been a well-behaved and well-adjusted prisoner, nor does the State dispute that the jury could have drawn favorable inferences from this testimony regarding petitioner's character and his probable future conduct if sentenced to life in prison. Although it is true that any such inferences would not relate specifically to petitioner's culpability for the crime he committed, see Koon I, supra, at 536, 298 S. E. 2d, at 774, there is no question but that such inferences would be "mitigating" in the sense that
they might serve "as a basis for a sentence less than death." Lockett, supra, at 604. Consideration of a defendant's past conduct as indicative of his probable future behavior is an inevitable and not undesirable element of criminal sentencing: "any sentencing authority must predict a convicted person's probable future conduct when it engages in the process of determining what punishment to impose," Jurek v. Texas, 428 U.S. 262, 275 (1976) (opinion of Stewart, POWELL, and STEVENS, JJ.). The Court has therefore held that evidence that a defendant would in the future pose a danger to the community if he were not executed may be treated as establishing an "aggravating factor" for purposes of capital sentencing, Jurek v. Texas, supra ; see also Barefoot v. Estelle, 463 U.S. 880 (1983). Likewise, evidence that the defendant would not pose a danger if spared (but incarcerated) must be considered potentially mitigating.*fn1 Under Eddings, such evidence may not be excluded from the sentencer's consideration.
The State advances several arguments as to why the exclusion of petitioner's proffered evidence was, nonetheless, not erroneous. First, the State contends that the trial court ruled only that petitioner's witnesses could not offer incompetent lay opinion testimony regarding petitioner's ability to adjust to prison life in the future. Eddings, the State argues, does not displace reasonable state-law rules regarding the ...