As explained above, the second Teague exception is available only if the new rule “alter[s] our understanding of the bedrock procedural elements” ’ essential to the fairness of a proceeding.” Sawyer v. Smith, 497 U. S. 227, 242 (1990) (quoting Teague v. Lane, 489 U. S. 288, 311 (1989) (plurality opinion), in turn quoting Mackey v. United States, 401 U. S. 667, 693 (1971) (Harlan, J., concurring in judgments in part and dissenting in part) (emphasis added)). Classifying an error as structural does not necessarily alter our understanding of these bedrock procedural elements. Nor can it be said that all new rules relating to due process (or even the “fundamental requirements of due process,” see post, at 674 (dissenting opinion)) alter such understanding. See, e. g., Sawyer, supra, at 244 (<HOLDING>); O’Dell v. Netherland, 521 U. S. 151, 167
holding that the rule in caldwell v mississippi 472 u s 320 1985 did not fit within the second teague exception even though it added to an existing guarantee of due process protection against fundamental unfairness holding that the rule in simmons v south carolina 512 u s 154 1994 which has been described as serving one of the hallmarks of due process id at 175 oconnor j concurring in judgment did not fit within the second teague exception holding that exclusion of hearsay statements violated due process even though statements were not admissible under mississippi law which did not recognize declarations against penal interest as a exception to the rule against hearsay holding that the due process clause contained in the colorado constitution encompasses a guarantee of equal protection holding that rule which provided an additional measure of protection to existing prohibition on prosecutorial remarks that render a proceeding fundamentally unfair was not an absolute prerequisite to fundamental fairness  that would fall within the second teague exception