opinion: Justice Stevens
  delivered the opinion of the Court.
  Respondent entered a plea of not guilty by reason of insanity to a charge of sexual battery. At his trial in the Circuit Court for Sarasota County, Florida, the prosecutor argued that respondent’s silence after receiving Miranda warnings was evidence of his sanity. The question presented is whether such use of a defendant’s silence violates the Due Process Clause of the Fourteenth Amendment as construed in Doyle v. Ohio, 426 U. S. 610 (1976).
  HH
  The battery occurred in woods near a beach in the vicinity of Sarasota, Florida. After respondent released his victim, she drove directly to the police station to report the incident. Based on her description, Officer Pilifant identified respondent on the beach and placed him under arrest about two hours after the assault occurred. After handcuffing him, the officer gave respondent the warnings required by our decision in Miranda v. Arizona, 384 U. S. 436, 467-473 (1966). Specifically, Officer Pilifant stated:
  “You have a right to remain silent. Anything you say can and will be used against you in a court of law. You have the right to talk to a lawyer and have him present with you while you are being questioned. If you cannot afford to hire a lawyer one will be appointed to represent you before any questioning if you wish. You can decide at any time to exercise these rights and not answer any questions or make any statements. Do you understand each of these rights I have explained to you? Having these rights in mind do you wish to talk to us now?” App. 73.
  Respondent replied by stating that he understood his rights and that he wanted to talk to an attorney before making any statement. The Miranda warnings were repeated by Officer Pilifant while driving to the police station and reiterated by Detective Jolley after they arrived at the station. Each time that respondent was asked “if he wished to give up the right to remain silent,” he declined, stating that he wanted to talk to an attorney. App. 77.
  Under Florida law, when a defendant pleads not guilty by reason of insanity and when his evidence is sufficient to raise a reasonable doubt about his sanity, the State has the burden of proving sanity beyond a reasonable doubt. In his case in chief, the prosecutor introduced the testimony of Officer Pilifant and Detective Jolley. They described the occasions on which respondent had exercised his right to remain silent and had expressed a desire to consult counsel before answering any questions. Both officers repeated the several colloquies with respondent. In his defense, respondent did not testify, but two psychiatrists expressed the opinion that he was a paranoid schizophrenic who had been unable to distinguish right from wrong at the time of the alleged offense. In rebuttal, the prosecutor relied on a third psychiatrist who expressed a contrary opinion.
  In his closing argument, over defense counsel’s objection, the prosecutor reviewed the testimony of Officer Pilifant and Detective Jolley and suggested that respondent’s repeated refusals to answer questions without first consulting an attorney demonstrated a degree of comprehension that was inconsistent with his claim of insanity. The jury found respondent guilty and the judge sentenced him to life imprisonment.
  By a 2-to-l vote, the Florida Court of Appeal for the Second District affirmed the conviction. Greenfield v. State, 337 So. 2d 1021 (1976). After noting that “prosecutorial comment relating to a defendant’s insistence on his right to remain silent generally constitutes reversible error,” id., at 1022, the majority held that the general rule did not apply to a case in which an insanity plea had been filed. The dissenting judge suggested that the application of the general rule would not have prejudiced the prosecution because the “questions and answers could have been couched in such a manner as to permit the officer to convey to the jury the fact that the appellant carried on a perfectly rational conversation without specifically stating that he chose to avail himself of his right to remain silent.” Id., at 1023.
  The Florida Supreme Court granted respondent’s petition for certiorari and summarily remanded the case to the Court of Appeal for reconsideration in light of Clark v. State, 363 So. 2d 331 (1978), a case in which it had held that improper comment on a defendant’s silence was constitutional error re viewable on appeal if an adequate contemporaneous objection was made either at the time the evidence was introduced or at the time of the prosecutor’s comment. Greenfield v. State, 364 So. 2d 885 (1978). On reconsideration, the Court of Appeal adhered to its earlier decision.
  Having exhausted his state remedies, respondent filed a petition for a writ of habeas corpus in the Federal District Court. The petition was referred to a Magistrate. The State argued that the silence issue was barred because respondent’s counsel had failed to make an adequate objection. The Magistrate concluded that federal review of the claim was not foreclosed because counsel had objected to the prosecutor’s closing argument and because the Florida Court of Appeal had rejected the claim on its merits. The Magistrate, however, agreed with the Florida courts’ disposition of the merits and recommended that the habeas corpus petition be denied. The District Court accepted that recommendation.
  The United States Court of Appeals for the Eleventh Circuit reversed. 741 F. 2d 329 (1984). Disagreeing with two other Federal Courts of Appeals — but not with the position taken by the Florida Supreme Court in a case decided after this respondent had exhausted his state remedies, see State v. Burwick, 442 So. 2d 944 (1983), cert. denied, 466 U. S. 931 (1984) — the Court of Appeals held that under the reasoning of Doyle v. Ohio, 426 U. S. 610 (1976), respondent was entitled to a new trial. We agree.
  i — I I — I
  In Doyle, the defendants had taken the witness stand and offered an exculpatory explanation for their participation in what the State’s evidence had portrayed as a routine marihuana transaction. On cross-examination the prosecutor impeached their testimony by asking them why they had not explained their conduct at the time of their arrest. The Court held that such cross-examination was fundamentally unfair and therefore violated the Due Process Clause of the Fourteenth Amendment.
  The source of the unfairness was the implicit assurance contained in the Miranda warnings “that silence will carry no penalty.” The critical importance of the implied promise that is conveyed to an arrested person by the Miranda warnings has been repeatedly confirmed in subsequent decisions. Thus, in Fletcher v. Weir, 455 U. S. 603, 606 (1982), we explained:
  “In Jenkins [v. Anderson, 447 U. S. 231 (1980)], as in other post-Doyle cases, we have consistently explained Doyle as a case where the government had induced silence by implicitly assuring the defendant that his silence would not be used against him. In Roberts v. United States, 445 U. S. 552, 561 (1980), we observed that the postconviction, presentencing silence of the defendant did not resemble ‘postarrest silence that may be induced by the assurances contained in Miranda warnings.’ In Jenkins, we noted that the failure to speak involved in that case occurred before the defendant was taken into custody and was given his Miranda warnings, commenting that no governmental action induced the defendant to remain silent before his arrest. 447 U. S., at 239-240. Finally, in Anderson v. Charles, 447 U. S. 404, 407-408 (1980), we explained that use of silence for impeachment was fundamentally unfair in Doyle because ‘Miranda warnings inform a person of his right to remain silent and assure him, at least implicitly, that his silence will not be used against him. . . . Doyle bars the use against a criminal defendant of silence maintained after receipt of governmental assurances.’”
  Since Fletcher, moreover, we have continued to reiterate our view that Doyle rests on “the fundamental unfairness of implicitly assuring a suspect that his silence will not be used against him and then using his silence to impeach an explanation subsequently offered at trial.” South Dakota v. Neville, 459 U. S. 553, 565 (1983). Doyle and subsequent cases have thus made clear that breaching the implied assurance of the Miranda warnings is an affront to the fundamental fairness that the Due Process Clause requires.
  The Florida Attorney General argues that Doyle does not control this case because proof of sanity is significantly different from proof of the commission of the underlying offense, and that the Doyle due process rationale thus does not apply. At the outset, we note that, in this case, unlike Doyle and its progeny, the silence was used as affirmative proof in the case in chief, not as impeachment. The Florida Attorney General argues that an insanity defense should be viewed as an “affirmative defense,” and that the use of silence to overcome an insanity defense should thus be viewed as impeachment. Without accepting that argument, or its characterization of the insanity defense, we address the claim that the Doyle due process analysis should not prevent the use of post-Miranda warnings silence to overcome an insanity defense.
  We find no warrant for the claimed distinction in the reasoning of Doyle and of subsequent cases. The point of the Doyle holding is that it is fundamentally unfair to promise an arrested person that his silence will not be used against him and thereafter to breach that promise by using the silence to impeach his trial testimony. It is equally unfair to breach that promise by using silence to overcome a defendant’s plea of insanity. In both situations, the State gives warnings to protect constitutional rights and implicitly promises that any exercise of those rights will not be penalized. In both situations, the State then seeks to make use of the defendant’s exercise of those rights in obtaining his conviction. The implicit promise, the breach, and the consequent penalty are identical in both situations.
  The Florida Attorney General argues, however, that introduction of the evidence of respondent’s -post-Miranda warnings silence no more violates the Constitution than did the reference to a defendant’s refusal to take a blood-alcohol test in South Dakota v. Neville, supra. In Neville, we rejected the due process challenge — and the attempt to rely on Doyle — because of the important differences between the refusal to take a blood-alcohol test and the post-Miranda warnings silence. We noted that, unlike the refusal to take an optional blood-alcohol test, the right of silence after Miranda warnings is of constitutional dimension. 459 U. S., at 565. We also noted that, unlike the state warning about the refusal to take the blood-alcohol test (which expressly advised Neville that his refusal could be used to deprive him of his driving privileges), Miranda warnings contain implied assurances that silence will not be used against the suspect. 459 U. S., at 565-566. Both Doyle elements —the constitutional dimension and the implied assurance — are equally present when post-Miranda warnings silence is used to prove sanity. Unlike Neville, therefore, and like Doyle, Greenfield received “the sort of implicit promise to forgo use of evidence that would unfairly ‘trick’ [him] if the evidence were later offered against him at trial.” 459 U. S., at 566.
  The Florida Attorney General further contends that a suspect’s comprehension of Miranda warnings, as evidenced by his silence, is far more probative of sanity than of commission of the underlying offense. He therefore argues that the reliance on the “insolubly ambiguous” character of the post-Miranda warnings silence in the Doyle opinion, 426 U. S., at 617, is inappropriate in the context of an insanity defense. We need not evaluate the probative value of respondent’s silence to reject this argument. For the ambiguity of the defendants’ silence in Doyle merely added weight to the Court’s principal rationale, which rested on the implied assurance contained in the Miranda warning. See South Dakota v. Neville, 459 U. S., at 564-565; Jenkins v. Anderson, 447 U. S. 231, 239-240 (1980). The Attorney General’s argument about the probative value of silence therefore fails entirely to meet the problem of fundamental unfairness that flows from the State’s breach of its implied assurances.
  Finally, the Florida Attorney General argues that it is vitally important to be able to present evidence of a defendant’s sanity at the time of the offense and shortly thereafter. However, as the dissenting judge in the Florida Court of Appeal recognized in this very case, the State’s legitimate interest in proving that the defendant’s behavior appeared to be rational at the time of his arrest could have been served by carefully framed questions that avoided any mention of the defendant’s exercise of his constitutional rights to remain silent and to consult counsel. What is impermissible is the evidentiary use of an individual’s exercise of his constitutional rights after the State’s assurance that the invocation of those rights will not be penalized.
  In Doyle, we held that Miranda warnings contain an implied promise, rooted in the Constitution, that “silence will carry no penalty.” 426 U. S., at 618. Our conclusion that it was fundamentally unfair for the Ohio prosecutor to breach that promise by using the defendants’ postarrest, post-Miranda warnings silence to impeach their trial testimony requires us also to conclude that it was fundamentally unfair for the Florida prosecutor to breach the officers’ promise to respondent by using his postarrest, post-Miranda warnings silence as evidence of his sanity.
  The judgment of the Court of Appeals is affirmed.
  It is so ordered.
  See Farrell v. State, 101 So. 2d 130, 133 (Fla. 1958) (“when there is testimony of insanity sufficient to present a reasonable doubt of sanity the presumption [of sanity] vanishes. The defendant is then entitled to an acquittal if the state does not overcome the reasonable doubt”), cited in Greenfield v. State, 337 So. 2d 1021, 1023, n. 2 (Fla. App. 1976).
  He argued, in part:
  “He goes to the ear and the officer reads him his Miranda rights. Does he say he doesn’t understand them? Does he say ‘what’s going on?’ No. He says ‘I understand my rights. I do not want to speak to you. I want to speak to an attorney.’ Again an occasion of a person who knows what’s going on around his surroundings, and knows the consequences of his act. Even down — as going down [to] the car as you recollect Officer Pil[i]fant said he explained what Miranda rights meant and the guy said — and Mr. Greenfield said ‘I appreciate that, thanks a lot for telling me that.’ And here we are to believe that this person didn’t know what he was doing at the time of the act, and then even down at the station, according to Detective Jolley — He’s down there. He says, ‘Have you been read your Miranda rights?’ ‘Yes, I have.’ ‘Do you want to talk?’ ‘No.’ ‘Do you want to talk to an attorney?’ ‘Yes.’ And after he talked to the attorney again he will not speak. Again another physical overt indication by the defendant....
  “So here again we must take this in consideration as to his guilt or innocence, in regards to sanity or insanity.” App. 96-98.
  The Florida Attorney General did not object to the Magistrate’s conclusion that the Florida Court of Appeal had rejected respondent’s claim on its merits. In his petition for rehearing in the United States Court of Appeals for the Eleventh Circuit, the Attorney General renewed the argument that the postarrest, post -Miranda warnings silence issue was barred by Wainwright v. Sykes, 433 U. S. 72 (1977). He advances the same argument in this Court. However, as the Magistrate concluded, the Florida appellate court clearly addressed the issue on the merits. Thus, we must reject the Attorney General’s argument. See Ulster County Court v. Allen, 442 U. S. 140, 149 (1979); Mullaney v. Wilbur, 421 U. S. 684, 704, n. (1975) (Rehnquist, J., concurring). Cf. Franks v. Delaware, 438 U. S. 154, 161-162 (1978); Raley v. Ohio, 360 U. S. 423, 436-437 (1959); Manhattan Life Insurance Co. v. Cohen, 234 U. S. 123, 134 (1914).
  See Sulie v. Duckworth, 689 F. 2d 128 (CA7 1982), cert. denied, 460 U. S. 1043 (1983); United States v. Trujillo, 578 F. 2d 285 (CA10), cert. denied, 439 U. S. 858 (1978).
  “Moreover, while it is true that the Miranda warnings contain no express assurance that silence will carry no penalty, such assurance is implicit to any person who receives the warnings. In such circumstances, it would be fundamentally unfair and a deprivation of due process to allow the arrested person’s silence to be used to impeach an explanation subsequently offered at trial. MR. Justice White, concurring in the judgment in United States v. Hale, [422 U. S.], at 182-188, put it very well:
  “ ‘[W]hen a person under arrest is informed, as Miranda requires, that he may remain silent, that anything he says may be used against him, and that he may have an attorney if he wishes, it seems to me that it does not comport with due process to permit the prosecution during the trial to call attention to his silence at the time of arrest and to insist that because he did not speak about the facts of the case at that time, as he was told he need not do, an unfavorable inference might be drawn as to the truth of his trial testimony. . . . Surely Hale was not informed here that his silence, as well as his words, could be used against him at trial. Indeed, anyone would reasonably conclude from Miranda warnings that this would not be the case.’” Doyle v. Ohio, 426 U. S., at 618-619 (footnotes omitted).
  In United States v. Hale, 422 U. S. 171 (1975), the Court had held that the use of postarrest, post-Miranda warnings silence was impermissible in federal prosecutions. The Court based its holding on its supervisory power in federal proceedings and left open the constitutional question. Justice White’s concurrence argued that the use violated due process, and it was that view the Court adopted in Doyle.
  That this “fundamental unfairness” derives from the implicit assurances of the Miranda warnings is supported by our holdings that due process is not violated by the impeachment use of pre-Miranda warnings silence, either before arrest, Jenkins v. Anderson, 447 U. S. 231 (1980), or after arrest, Fletcher v. Weir, 455 U. S. 603 (1982), or of post-Miranda warnings statements, Anderson v. Charles, 447 U. S. 404 (1980); nor is it violated by the use of a refusal to take a state test that does not involve Miranda-]ike warnings, Neville.
  Notably, the Court in Doyle did not rely on the contention that Ohio had violated the defendants’ Fifth Amendment privilege against self-incrimination by asking the jury to draw an inference of guilt from the exercise of their constitutional right to remain silent. Cf. Griffin v. Cali- fomia, 380 U. S. 609 (1965) (Fifth Amendment prohibits prosecutorial comment on defendant’s refusal to testify).
  The constitutional violation might thus be especially egregious because, unlike Doyle, there was no risk “that exclusion of the evidence [would] merely provide a shield for perjury. ” 426 U. S., at 626 (Stevens, J., dissenting).
  Cf. n. 1, supra.
  To the extent that the Attorney General seeks to rely on Neville’s Fifth Amendment holding, his argument is inapposite because the Doyle analysis rests on the Due Process Clause, not the Fifth Amendment.
  We note, however, that the Florida Supreme Court does not share the Florida Attorney General’s view about the probative value of silence in an insanity context. As the Florida court wrote in State v. Burwick, 442 So. 2d 944, 948 (1983):
  “Post-arrest, post -Miranda silence is deemed to have dubious probative value by reason of the many and ambiguous explanations for such silence. 422 U. S. at 180 ... . Contrary to what Greenfield intimates, these ambiguities attendant to post-Miranda silence do not suddenly disappear when an arrestee’s mental condition is brought into issue. The same evidentiary problems addressed by the Supreme Court in Hale are present in the case before us. For example, one could reasonably conclude that custodial interrogation might intimidate a mentally unstable person to silence. Likewise, an emotionally disturbed person could be reasonably thought to rely on the assurances given during a Miranda warning and thereafter choose to remain silent. In sum, just what induces post-arrest, post-Miranda silence remains as much a mystery today as it did at the time of the Hale decision. Silence in the face of accusation is an enigma and should not be determinative of one’s mental condition just as it is not determinative of one’s guilt. Accordingly, the state should not be permitted to confirm Burwick’s mental state with evidence of his post-Miranda silence.”
  Several commentators have also emphasized that, particularly in light of later eases, Doyle’s probativeness rationale is secondary to its implied assurance rationale. See, e. g., Note, Protecting Doyle Rights After Anderson v. Charles: The Problem of Partial Silence, 69 Va. L. Rev. 155, 165, n. 56 (1983); Clark, Impeachment With Post-Arrest Silence: The Emergence of a “New Federalism” Approach, 19 Am. Crim. L. Rev. 751, 759 (1982); The Supreme Court, 1979 Term, 94 Harv. L. Rev. 77, 84-85 (1980).
  In his petition and brief, the Attorney General has not contested the Eleventh Circuit’s view that the prosecutorial comment was directed at the “defendant’s post-Miranda warning silence,” 741 F. 2d 329, 333 (1984), or its conclusion that this comment, if erroneous, was not harmless, id., at 336. Nor has respondent contested the point that a prosecutor may legitimately inquire into and comment upon “purely ‘demeanor’ or ‘behavior’ evidence.” Brief for Respondent 14. With respect to post-Miranda warnings “silence,” we point out that silence does not mean only muteness; it includes the statement of a desire to remain silent, as well as of a desire to remain silent until an attorney has been consulted.
  This conclusion is supported by a number of state decisions, in addition to that of Florida. See Commonwealth v. Mahdi, 388 Mass. 679, 448 N. E. 2d 704 (1983); People v. Vanda, 111 Ill. App. 3d 551, 444 N. E. 2d 609 (1982), cert. denied, 464 U. S. 841 (1983); People v. Schindler, 114 Cal. App. 3d 178, 170 Cal. Rptr. 461 (1980).
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