In Arizona v. Fulminante (1991) 499 U.S. 279, the defendant, while in custody on an unrelated charge, confessed to a paid jailhouse informant that he had sexually assaulted and murdered his 11-year-old stepdaughter. (Fulminante, supra, 499 U.S. at pp. 282-283.) The jailhouse informant, posing as an organized crime figure, had promised, in exchange for the confession, "protection" from "tough treatment" the defendant was receiving in prison due to the rumors of his involvement in the sexual assault and murder of a child. (Id. at p. 283.) After the defendant was released from prison, he repeated his confession to the informant's fiance. (Id. at pp. 283-284.) The United States Supreme Court found that the initial confession to the informant was "coerced," as it was given in exchange for the promised protection from assault by other inmates. (Id. at p. 287.) Admitting the initial coerced confession was not "harmless error," in light of the subsequent "voluntary" confession to the informant's fiance, because the jury "might have believed that the two confessions reinforced and corroborated each other." (Id. at p. 299.) The Supreme Court cited a wide range of errors susceptible to harmless error analysis. According to the Supreme Court, 'the common thread connecting those cases is that each involved "trial error"--error which occurred during the presentation of the case ....' (Id. at p. 307.) An error in the trial process itself does not require automatic reversal because a court may quantitatively assess such an error in the context of other evidence presented in order to determine whether the error was harmless beyond a reasonable doubt. (Id. at pp. 307-308.) In applying harmless error analysis to these many different constitutional violations, the court explained the harmless error doctrine is 'essential to preserve the "principle that the central purpose of a criminal trial is to decide the factual question of the defendant's guilt or innocence, and promotes public respect for the criminal process by focusing on the underlying fairness of the trial rather than on the virtually inevitable presence of immaterial error."' (Id. at p. 308.) "By comparison, 'structural' error or a 'structural defect in the constitution of the trial mechanism ... affecting the framework within which the trial proceeds, rather than simply an error in the trial process itself' defies analysis by a harmless error standard. (Arizona v. Fulminante, supra, 499 U.S. at pp. 309-310.) A structural error requires reversal without regard to the strength of the evidence or other circumstances. (Id. at p. 310.) "The United States Supreme Court has found structural errors, however, only in a very limited class of cases: the total deprivation of the right to counsel at trial , a biased judge , unlawful exclusion of members of the defendant's race from a grand jury , denial of the right to self-representation at trial , denial of the right to a public trial , and erroneous reasonable-doubt instruction to jury . (Arizona v. Fulminante, supra, 499 U.S. at pp. 309-310.) With regard to such structural errors, Fulminante explained: '"Without these basic protections, a criminal trial cannot reliably serve its function as a vehicle for determination of guilt or innocence, and no criminal punishment may be regarded as fundamentally fair."' (Id. at p. 310.)