What is the standard for determining prejudicial impact of a jury instruction in a habeas case?

3 Smith suggests that the standard for determining the prejudicial impact of a jury instruction is whether it is "more probable than not" that it "materially affected the verdict." See United States v. Rhodes, 713 F.2d 463, 475 (9th Cir.), cert. denied, 464 U.S. 1012 (1983). Rhodes was a challenge to jury instructions on direct appeal of a federal conviction, not a habeas claim. The type of instruction that may raise a cognizable claim in a habeas corpus petition, by contrast, is one that implicates a due process right such as the presumption of innocence, rather than one that might have affected the verdict but did not implicate a constitutional right. See, e.g., Sandstrom v. Montana, 442 U.S. 510 (1979).