Cite as: 518 U. S. 37 (1996)
O'Connor, J., dissenting
requirement of the mental state of "purposely" or "knowingly" to prevent the jury from considering evidence of voluntary intoxication, where that category of evidence was relevant to establishment of that mental-state element. 272 Mont., at 122-123, 900 P. 2d, at 265-266.
Where the defendant may introduce evidence to negate a subjective mental-state element, the prosecution must work to overcome whatever doubts the defense has raised about the existence of the required mental state. On the other hand, if the defendant may not introduce evidence that might create doubt in the factfinder's mind as to whether that element was met, the prosecution will find its job so much the easier. A subjective mental state is generally proved only circumstantially. If a jury may not consider the defendant's evidence of his mental state, the jury may impute to the defendant the culpability of a mental state he did not possess.
In Martin v. Ohio, 480 U. S. 228 (1987), the Court considered an Ohio statute providing that a defendant bore the burden of proving, by a preponderance of the evidence, an affirmative defense such as self-defense. We held that placing that burden on the defendant did not violate due process. The Court noted in explanation that it would nevertheless have been error to instruct the jury that "self-defense evidence could not be considered in determining whether there was a reasonable doubt about the State's case" where Ohio's definition of the intent element made self-defense evidence relevant to the State's burden. Id., at 233-234. "Such an instruction would relieve the State of its burden and plainly run afoul of Winship's mandate." Id., at 234. In other words, the State's right to shift the burden of proving an affirmative defense did not include the power to prevent the defendant from attempting to prove self-defense in an effort to cast doubt on the State's case. Dictum or not, this observation explained our reasoning and is similarly applicable here, where the State has benefited from the defendant's in-
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