Cite as: 508 U. S. 333 (1993)
Opinion of the Court
In concluding that this defect violated due process, the Falconer court relied on Cupp v. Naughten, supra. That case involved a due process challenge to a jury instruction that witnesses are presumed to tell the truth, which the defendant claimed had the effect of shifting the burden of proof on his innocence. Because the jury had been explicitly instructed on the defendant's presumption of innocence as well as the State's burden of proving guilt beyond a reasonable doubt, we held that the instruction did not amount to a constitutional violation. See 414 U. S., at 149.
We think Cupp is an unlikely progenitor of the rule announced in Falconer, a view now shared by the Seventh Circuit. The cases following Cupp in the Winship line establish that States must prove guilt beyond a reasonable doubt with respect to every element of the offense charged, but that they may place on defendants the burden of proving affirmative defenses. See Martin v. Ohio, 480 U. S. 228 (1987); Patterson v. New York, 432 U. S. 197 (1977). The State argues that these later cases support the proposition that any error committed in instructing a jury with respect to an affirmative defense, which does not lessen the State's Winship burden in proving every element of the offense charged beyond a reasonable doubt, is one wholly of state law. Cf. Engle v. Isaac, 456 U. S. 107, 119-121, and n. 21 (1982) (challenge to correctness of self-defense instructions under state law provides no basis for federal habeas relief). We need not address this contention other than to say that cases like Patterson and Martin make it crystal clear that Cupp does not compel the result reached in Falconer.
In its decision in the present case, the Court of Appeals offered two additional cases which it believed did dictate the result in Falconer. The first is Boyde v. California, supra. There, we clarified the standard for reviewing on federal habeas a claim that ambiguous jury instructions impermissibly restricted the jury's consideration of "constitutionally relevant evidence." 494 U. S., at 380. Although Boyde was de-
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