Mr. Justice Black
delivered the opinion of the Court.
The Fifth Amendment to the United States Constitution provides in unequivocal terms that no person may “be compelled in any criminal case to be a witness against himself.” To protect this right Congress has declared that the failure of a defendant to testify in his own defense “shall not create any presumption against him.” Ordinarily, the effectuation of this protection is a relatively simple matter — if the defendant chooses not to take the stand, no comment or argument about his failure to testify is permitted. But where for any reason it becomes necessary to try a particular charge more than one time, a more complicated problem may be presented. For a defendant may choose to remain silent at his first trial and then decide to take the stand at a subsequent trial. When this occurs, questions arise as to the propriety of comment or argument in the second trial based upon the defendant’s failure to take the stand at his previous trial. This case turns upon such a question.
Petitioner has been tried three times in the District Court for the District of Columbia upon an indictment charging that he had committed first-degree murder under a felony-murder statute. In all three trials, petitioner’s chief defense has been insanity but, on each occasion, the jury has rejected this defense and returned a verdict of guilty upon which the District of Columbia’s mandatory death sentence has been imposed. After the first two trials, in which petitioner did not testify, the convictions and death sentences were set aside on, the basis of trial errors that the Court of Appeals found had prevented a proper consideration of the case by the jury. At the third trial, in an apparent effort to bolster the contention of insanity, petitioner was placed upon the stand and asked a number of questions by defense counsel — a maneuver obviously made for the purpose of giving the jury an opportunity directly to observe the functioning of petitioner’s mental processes in the hope that such an exhibition would persuade them that his memory and mental comprehension were defective. Petitioner’s responses to these questions were aptly described by the court below as “gibberish without meaning.”
Upon cross-examination, the prosecutor attempted without noticeable success to demonstrate that these irrational answers were given by petitioner in furtherance of his plan to feign a mental weakness that did not exist. To this end, the prosecutor asked petitioner a number of questions about statements petitioner had allegedly made subsequent to his arrest, apparently in the hope that one of these questions would surprise petitioner and provoke a sensible response. When petitioner continued to talk in the same manner that he had used upon direct examination, the prosecutor concluded his cross-examination with the following remarks in the form of questions: “Willie, you were tried on two other occasions.” And, “This is the first time you have gone on the stand, isn’t it, Willie?”
The defense moved immediately for a mistrial on the ground that it was highly prejudicial for the prosecutor to inform the jury of the defendant’s failure to take the stand in his previous trials. The prosecutor defended his actions on the ground that this “is a fact that the Jury is entitled to know.” The trial judge agreed with the prosecutor, denied the motion for a mistrial, and the trial proceeded, culminating in the third verdict of guilty and death sentence. On appeal, the case was heard by all nine members of the Court of Appeals sitting en banc and was affirmed by a 5-4 vote — the majority concluding that the issue was controlled by the decision of this Court in Raffel v. United States, and the minority concluding that the issue was controlled by our decision in Grunewald v. United States. We granted certiorari to consider whether it was error for the trial court to deny the motion for a mistrial under the circumstances.
In this Court, the Government concedes that the question put to the defendant about his prior failures to testify cannot be justified under Raffel, Grünewald, or any other of this Court’s prior decisions. This concession, which we accept as proper, rests upon the Government’s recognition of the fact that in no case has this Court intimated that there is such a basic inconsistency between silence at one trial and taking the stand at a subsequent trial that the fact of prior silence can be used to impeach any testimony which a defendant elects to give at a later trial. The Raffel case, relied upon by the majority below, involved a situation in which Raffel had sat silent at his first trial in the face of testimony by a government agent that Raffel had previously made admissions pointing to his guilt. On a second trial, Raffel took the stand and denied the truth of this same testimony offered by the same witness. Under these circumstances, this Court held that Raffel’s silence at the first trial could be shown in order to discredit his testimony at the second trial on the theory that the silence itself constituted an admission as to the truth of the agent’s testimony. The result was that Raffel’s silence at the first trial was held properly admitted to impeach the specific testimony he offered at the second trial. Here, on the other hand, the defendant’s entire “testimony” comprised nothing more than “gibberish without meaning” with the result that there was no specific testimony to impeach. Any attempt to impeach this defendant as a witness could therefore have related only to his demeanor on the stand, and, indeed, the majority below expressly rested its conclusion upon the view that the prosecution had the right under Raffel to test the genuineness of this sort of “demeanor-evidence” by questions as to why it was not offered at previous trials. But if Raffel could properly be read as standing for this proposition, such questions would be permissible in every instance, for whenever a witness takes the stand, he necessarily puts the genuineness of his demeanor into issue. The Government quite properly concedes that this cannot be the law since it would conflict with the precise holding of this Court in the Grünewald case.
Despite this concession, however, the Government persists in the contention that petitioner’s conviction should be upheld, arguing that the error committed was harmless and could not have affected the jury’s verdict. This argument is rested upon three grounds: first, that the jury may not even have heard the improper question; secondly, that even if the jury did hear the question, it may not have inferred that petitioner in fact did not testify at his previous trial; and, finally, that even if the jury did infer that petitioner did not testify previously, no inference adverse to petitioner would have been drawn from this fact. The first two of these grounds can be quickly disposed of. We can think of no justification for ignoring the part of a record showing error on a mere conjecture that the jury might not have heard the testimony that part of the record represents. Nor do we believe it reasonable to argue that the jury trying this cáse would not have inferred that this defendant had failed to testify in his prior trials when the prosecutor asked, “This is the first time you have gone on the stand, isn’t it, Willie?” Indeed, the recognition that such an inference will in all likelihood be drawn from leading questions of this kind lies at the root of the long-established rule that such questions may not properly be put unless the inference, if drawn, would be factually true. Thus, the Government’s argument that the error was harmless must stand or fall upon the third ground it urges — that the jury’s awareness of petitioner’s failure to take the stand at his previous trials would not have prejudiced the consideration of his case. The disposition of this contention requires the statement of a few more of the relevant facts of the case.
In connection with the defense of insanity, petitioner had introduced evidence of both mental disease and mental defect, as those terms are applied in the relevant law of the District of Columbia. On the mental disease issue, the testimony was that petitioner was suffering from manic depressive psychosis, a disease which the record shows tends to fluctuate considerably in its manifestations from time to time. On the mental defect issue, the defense introduced evidence that petitioner had an intelligence level in the moronic class. The case went to the jury on both of these points, the jury being directed to acquit if it found the homicide to have been the product either of mental disease or mental defect. Petitioner’s “testimony” thus raised at least two different issues in the minds of the jury: first, whether petitioner was simply feigning this testimony; and, secondly, whether, if not, petitioner’s condition at the time of his third trial fairly represented his condition at the time of the act charged in the indictment.
We think it apparent that the jury’s awareness of petitioner’s failure to testify at his first two trials could have affected its deliberations on either or both of these issues. Thus, the jury might well have thought it likely that petitioner elected to feign this “testimony” out of desperation brought on by his failure to gain acquittal without it in the two previous trials. Similarly, even if the jury believed petitioner’s “testimony” was genuine, .it might have thought that petitioner’s condition was caused by a mental disease and concluded that it is unlikely that a disease that had manifested itself only one out of three times for exhibition at trial was active at the occasion of the homicide. Or, on the same assumption, it might have thought that petitioner’s failure to exhibit himself at the previous trials indicated that the condition manifested at this trial was the result of a worsening in his mental condition since those trials and, consequently, also since the commission of the acts charged in the indictment. There may be other ways in which the jury might have used the information improperly given it by the prosecution — we have mentioned more than enough already, however, to satisfy ourselves that the Government’s contention that the error was harmless must be rejected.
The Government’s final contention is that even if the error was prejudicial the conviction should be allowed to stand on the theory that the error was not sufficiently prejudicial to warrant the granting of a mistrial and the defense made no request for cautionary instructions. One answer to this argument is to be found in the Government’s own brief. For, in its argument regarding the possibility that the jury may not have been aware of the improper question, the Government stresses the fact that the question was not emphasized by any reference to it in the instructions to the jury. During the course of this argument the Government expressly recognizes that the danger of the situation would have been increased by a cautionary instruction in that such an instruction would have again brought the jury’s attention to petitioner’s prior failures to testify. Plainly, the defense was under no obligation to take such a risk. The motion for a mistrial was entirely appropriate and, indeed, necessary to protect the interests of petitioner.
We thus conclude that this conviction and sentence against petitioner cannot stand. In doing so, we agree with the point made by the Government in its brief — that it is regrettable when the concurrent findings of 36 jurors are not sufficient finally to terminate a case. But under our system, a man is entitled to the findings of 12 jurors on evidence fairly and properly presented to them. Petitioner may not be deprived of his life until that right is accorded him. That right was denied here by the prosecutor’s improper questions.
Reversed.
“In trial of all persons charged with the commission of offenses against the United States and in all proceedings in courts martial and courts of inquiry in any State, District, Possession or Territory, the person charged shall, at his own request, be a competent witness. His failure to make such request shall not create any presumption against him.” 62 Stat. 833, 18 U. S. C. § 3481.
Wilson v. United, States, 149 U. S. 60.
“Whoever, being of sound memory and discretion, kills another purposely, either of deliberate and premeditated malice or by means of poison, or in perpetrating or attempting to perpetrate any offense punishable by imprisonment in the penitentiary, or without purpose so to do kills another in perpetrating or in attempting to perpetrate any arson, as defined in section 22-401 or 22-402 of this Code, rape, mayhem, robbery, or kidnapping, or in perpetrating or in attempting to perpetrate any housebreaking while armed with or using a dangerous weapon, is guilty of murder in the first degree.” District of Columbia Code § 22-2401. (Emphasis supplied.)
Section 22-2404 of the District of Columbia Code provides: “The punishment of murder in the first degree shall be death by electrocution.”
The first conviction was set aside because of erroneous instructions on the defense of insanity. 94 U. S. App. D. C. 293, 214 F. 2d 879. The second conviction was set aside because of improper argument by the prosecutor. 101 U. S. App. D. C. 51, 247 F. 2d 42.
107 U. S. App. D. C. 159, 160, 275 F.2d 617, 618. The following excerpt from petitioner's testimony is entirely typical:
“Q. Who is your lawyer?
■“A. Well, I mean, I am my own lawyer, as far as my concern.
“Q. Have I been representing you here the last couple days?
“A. As far as I am concerned, you all look the same to me.
“Q. Do you know what is going on in this courtroom the last couple days?
“A. I ain’t asked about what is going on. It is up to you go on and describe yourself. I mean, don’t ask me. As far as I am just sitting here.
“Q. Did you ever hear the name Harry Honigman [the man with whose murder petitioner was charged] before?
“A. I haven’t.
“Q. Do you know you are charged with first degree murder ?
“A. As far as I am concerned, I ain’t charged with nothing.
“Q. What is first degree murder; do you know?
“A. I don’t know.”
The record reveals the following exchange at the conclusion of the cross-examination of petitioner by the prosecutor, a Mr. Smithson:
“Q. Willie, you were tried on two other occasions.
“A. Well, I don’t care how many occasions, how many case — you say case. I was a case man once in a time.
“Q. This is the first time you have gone on the stand, isn’t it, Willie?
“A. What?
"Q. This is the first time you have gone on the stand, isn’t it, Willie?
“A. I am always the stand; I am everything, I done told you.
“Mr. Smithson: That is all.”
107 U. S. App. D. C. 159, 275 F. 2d 617.
271 U. S. 494.
353 U. S. 391.
363 U. S. 818. The petition for certiorari also raised objections based upon other alleged errors during the course of the trial. In view of our disposition of the primary issue and because the actions complained of may not arise at any subsequent trial, we find it unnecessary to pass upon these other objections.
Thus, the majority reasoned: “The logical and permissible first step under Raffel v. United States, supra, was to have him say whether he had previously testified in order to lay the groundwork for developing an inconsistency inherent in the difference in his ‘demeanor-evidence’ in the two trials.” 107 U. S. App. D. C. 159, 167, 275 F. 2d 617, 625.
This is so because the defendant’s credibility is in issue whenever he testifies. If the failure to testify at a previous trial were to amount to evidence that testimony at a subsequent trial was feigned or perjurious, the fact of failure to testify would always be admissible.
The holding in Grünewald was that the defendant’s answers to certain questions were not inconsistent with his previous reliance upon the Fifth Amendment to excuse a refusal to answer those very same questions. Since defendant’s testimony placed his credibility in issue, the necessary implication of that holding is that his prior refusal to testify could not be used to impeach his general credibility.
III Wigmore, Evidence (3d ed.), § 780. Wigmore quotes Chitty, Practice of the Law, 2d ed., III, 901, for the proposition: “It is an established rule, as regards cross-examination, that a counsel'has no right, even in order to detect or catch a witness in a falsity, falsely to assume or pretend that the witness had previously sworn or stated differently to the fact, or that a matter had previously been proved when it had not.” This Court has previously recognized that principle. Berger v. United States, 295 U. S. 78, 84.
The difference between the terms “disease” and “defect” was explained in the charge to the jury in the following manner: “We'use ‘disease’ in the sense of a condition which is considered capable of either improving or deteriorating. We use ‘defect’ in the sense of a condition which is not considered capable of either improving or deteriorating, and which may be either congenital or the result of injury, or the residual effect of a physical or mental disease.”
These instructions stemmed from the test of criminal responsibility that prevails in the District of Columbia under the decision of the Court of Appeals in Durham v. United States, 94 U. S. App. D. C. 228, 214 F. 2d 862.
This second issue arises from the fact that the jury was not here trying the question whether petitioner was mentally competent to stand trial. Under the District of Columbia practice, that question is decided in a separate proceeding. See District of Columbia Code §24-301.
Johnson v. United States, 318 U. S. 189, relied upon by the Government, does not sustain its argument on this point. There the defense made no objection at all, choosing instead to rest its chances upon the verdict of the jury. Petitioner here made no such choice for he has repeatedly pressed his right to a mistrial, in the. District Court, in the Court of Appeals, and here.