¶1*722Arthur Lowy, Washington, D. C. (appointed by this Court) with whom Nathan Rubinstein, was on the brief for appellant.
¶2Robert Plotkin, Washington, D. C., and Paul Friedman for the Mental Health Law Project as amicus curiae.
¶3Edward C. McGuire, Asst. U. S. Atty., Washington, D. C., with whom Earl J. Silbert, U. S. Atty., John A. Terry, Stuart M. Gerson and David M. Bullock, Asst. U. S. Attys., Washington, D. C., were on the brief for appellee.
¶4Before BAZELON, Chief Judge, HAST-IE,* Senior Circuit Judge for the Third Circuit and ROBB, Circuit Judge.
¶5Opinion filed by Chief Judge BAZELON.
¶6Concurring opinion filed by Circuit Judge HASTIE.
¶7Dissenting opinión filed by Circuit Judge ROBB.
¶10These motions to vacate a plea of guilty (28 U.S.C. § 2255) and to withdraw the plea (Rule 32(d) of the Federal Rules of Criminal Procedure) are based on appellant’s claim of incompetence at the time the plea was entered. Since we find that the record does not “conclusively show that the prisoner is entitled to no relief,”1 it follows that the district court erred in denying these motions without a hearing.
¶11I.
¶12Appellant and a co-defendant were charged in a three-count indictment with *723armed robbery,2 robbery,3 and assault with a dangerous weapon.4 The charges stemmed from a robbery of a gas station and one Leon Henderson; $104 in cash and a $60 watch were taken.
¶13There were indications from the very outset that appellant was mentally deficient. At pretrial appointed counsel moved for a Miranda hearing, asserting that appellant had not knowingly and intelligently waived his Fifth Amendment rights. At the pretrial appearance, the prosecutor admitted that “there may be some difficulty with the confession” and that he “may not use it.”5 Papers filed in connection with the proceedings below reveal that appellant could not sign his name; when his signature was required, appellant printed his name in scrawling block letters.6
¶14Upon entry of the guilty plea on November 26,1973, when the trial court addressed appellant personally,7 he simply responded, “Yes, Ma’am” or “No, Ma’am” to all but one8 of the court’s queries.9 The complaining witness, Mr. Henderson, thereupon expressed to the court his belief that appellant was a “good” but “illiterate” man who must have been “put up to” the crime, and urged that he not be incarcerated.'10 Appellant’s counsel specifically suggested, and the court apparently agreed, that “in the presentence aspect of this case some attention [be] paid to the psychological aspect,” and that a suitable program of rehabilitation be devised.11
¶15Sentencing was delayed pending preparation of a presentence report and an evaluation of appellant’s suitability for rehabilita*724tion under the Narcotics Addict Rehabilitation Act.12 Appellant’s “extremely low level of intelligence” and his lack of any “concept of time” were stressed throughout the presentence report.13 The NARA staff found appellant’s narcotic addiction to be questionable, and recommended “special educational or vocational training”14 rather than NARA treatment, since “his mental capabilities would hinder him extremely in [NARA’s] type of intensive, therapeutic program.”15 Again, appellant’s low level of intelligence was noted, supported by the results of the Revised Beta Intelligence Test, on which appellant scored 57,16 and the Stanford Achievement Test, on which he scored 2.2, indicating that he operates “at slightly above the second grade level of academic achievement.”17
¶16At sentencing on March 28, 1974, counsel reminded the court of appellant’s “extraordinarily low intelligence,”18 and suggested probationary supervision. When asked about a pending marriage to an old girlfriend, appellant told the court that “we haven’t been together for about three years and we were getting married this month or last month, like she is expecting a kid.”19 The trial judge replied, “Not yours, I take it,” to which appellant responded, “I don’t *725know.”20 The court imposed a sentence of two to six years.
¶17After a motion for reconsideration and reduction of sentence was denied, appellant filed the present motions to vacate the plea of guilty under 28 U.S.C. § 2255 and to withdraw the plea under Rule 32(d), P.R.Cr. Pro.
¶18II.
¶19It is “fundamental to an adversary system of justice”21 that an individual whose “mental condition is such that he lacks the capacity to understand the nature and object of the proceedings against him, to consult with counsel, and to assist in preparing his defense”22 may not be subjected to a trial.23 The conviction of an accused who is mentally incompetent violates due process.24 Where the “circumstances generat[e] a substantial doubt as to the accused’s competence ... a suitable hearing must be held.”25
¶20It is axiomatic that an accused must be competent to enter a valid guilty plea: “A plea of guilty ... is itself a conviction. Like a verdict of a jury it is conclusive. More is not required; the court has nothing to do but give judgment and sentence.”26 A defendant who enters such a plea waives “his privilege against compulsory self-incrimination, his right to trial by jury, and his right to confront his accusers.”27 The test of validity of the waiver is whether it is “an intentional relinquishment or abandonment of a known right or privilege.”28 If a plea is not “equally voluntary and knowing, it has been obtained in violation of due process and is therefore void. Moreover, because a guilty plea is an admission of all the elements of a formal criminal charge, it cannot be truly voluntary unless the defendant *726possesses an understanding of the law in relation to the facts.”29
¶21A defendant’s competency must be assessed “with specific reference to the gravity of the decisions with which [he] is faced.”30 Whether an accused is capable of making the “reasoned choice”31 essential to the validity of a guilty plea and the waiver of constitutional rights such as the plea entails “depend[s] . . . upon the particular facts and circumstances surrounding [the] case, including the background, experience, and conduct of the accused.”32
¶22 A petitioner who lacked the capacity to have entered an intelligent plea may withdraw his plea pursuant to Rule 32(d), F.R.Cr.Pro.33 and/or collaterally attack his conviction and sentence pursuant to 28 U.S.C. § 2255.34One who seeks such relief must be offered an opportunity to present evidence at a hearing “[u]nless the motion and the files and records of the case conclusively show that the prisoner is entitled to no relief . . . .”35
¶23The trial court did not, and indeed could not, rely upon such a showing in the instant ease.36 Instead, it denied relief *727based on: (1) appellant’s failure to raise the competence issue prior to sentencing; (2) its personal observation of appellant and the apparent understanding appellant displayed, as evidenced by his affirmative responses, during the guilty plea colloquy; and (3) appellant’s admissions of his role in the robbery. These grounds, of course, do not support the denial of relief without a hearing.
¶24(1) The district court repeatedly emphasized that “[a]ll the factors raised as bases for withdrawal were known prior to sentencing.”37 The court observed that “[i]f the defendant’s lack of capacity was a truly serious claim, it certainly was apparent prior to sentencing, and would have been raised at that time.”38 This proposition reflects both a misapplication of the law, and a “basic failure of our criminal justice system to recognize that special provisions must sometimes be made for the mentally retarded.”39
¶25Rule 32(d) specifically provides for withdrawal of a plea after both conviction and sentencing.40 There is no time limitation for the filing of a 28 U.S.C. § 2255 motion.41 The Supreme Court has recognized that the failure to raise the competency issue prior to conviction is no bar to relief since “it is contradictory to argue that a defendant may be incompetent, and yet knowingly or intelligently ‘waive’ his right to have the court determine his capacity to stand trial.”42
¶26Although there were early signs suggesting retardation,43 appellant was first tested after entry of his plea. Counsel informed the court that only upon learning appellant’s IQ did he appreciate the import of those earlier signs and realize that appellant might have been incompetent.44 Counsel argued that
he was misled by defendant’s attitude and manner into believing that defendant understood the proceedings and the consequences of his plea of guilty. Defendant appeared to be agreeable to all suggestions, nodding to counsel as though he understood counsel’s explanation.45 (Emphasis added.)
¶27Counsel’s initial failure to recognize appellant’s retardation and appellant’s apparent acquiescence must be examined in the light of available research. For example, studies could be introduced at a proper hearing, subject to examination and cross-examination, indicating that the mentally retarded often demonstrate an exaggerated *728suggestibility and need to cooperate,46 and that retardation frequently goes undetected.47
¶28(2) Nor can the court’s reliance on its personal observations of appellant be determinative.48 Decisions of the Supreme Court49 and the various courts of appeals50 clearly indicate that the trial court’s observation of a defendant’s apparent rationality and comprehension is an insufficient basis for denying a hearing on a § 2255 motion raising the issue of competency. The impropriety of reliance on personal observation is highlighted in the case of a retarded defendant.
¶29And although the district court addressed appellant before accepting his plea, it is apparent that the standard Rule 1151 colloquy may prove an inadequate measure of the validity of a plea proffered by a *729defendant of questionable mental competence. As the Supreme Court observed, “[t]he nature of the inquiry required by Rule 11 must necessarily vary from case to case . . . . In all such inquiries, ‘[m]atters of reality, and not mere ritual, should be controlling.’ ”52
¶30(3) Finally, appellant’s guilt or innocence is not a proper basis for dispensing with an evidentiary hearing.53 While under Rule 32(d) “a failure to demonstrate innocence, or an admission of guilt, has ordinarily been considered fatal,54 relief may be accorded under 28 U.S.C. § 2255 regardless of petitioner’s guilt or innocence.55
¶31It may be argued that we should order withdrawal of appellant’s plea on the ground that the district court abused its discretion in failing to do so. But we believe that the interests of the appellant and the administration of criminal justice would best be served by a hearing to properly examine and assess the nature and extent of appellant’s disabilities. Such information is essential whether the issue is competency to stand trial, withdrawal of a plea, criminal responsibility or sentencing.56 Only with the light of such information can we hope to find the path to accommodating society’s need for order with its deeply-held *730concern for the dignity and worth of every human being.
¶32Reversed and Remanded.
¶108(concurring):
¶109Joining in Chief Judge Bazelon’s opinion, I add this concurring comment only because the dissenting opinion — erroneously, in my view — pictures this decision as a jurisprudential sport that “licenses every illiterate moron to violate the law with impunity.” In actuality this decision merely recognizes and implements the fundamental and firmly established rule that “if a defendant’s guilty plea is not equally voluntary and knowing, it has been obtained in violation of due process and is therefore void.” See McCarthy v. United States, 394 U.S. 459, 466, 89 S.Ct. 1166, 1171, 22 L.Ed.2d 418, 425 (1968).
¶110By proper post-conviction procedure in the trial court, appellant Masthers put in issue the question whether his guilty plea had been “voluntary and knowing.” And on that issue he asked for an evidentiary hearing.
¶111The district court denied an evidentiary hearing and found the plea valid on the basis of the original showing that had been made in open court before acceptance of the plea. Thus the issue here is simply whether the district court should have permitted the appellant to establish, if he could, in this post-conviction proceeding that his plea was not, as it had seemed at arraignment, voluntary and knowing.
¶112As Chief Judge Bazelon points out, data before us on this appeal, but. not before the district court at arraignment, strongly indicates that Masthers’ level of intelligence is so low and his mental retardation so great that all that was said and done on the occasion of his pleading did not irrebuttably establish comprehension of the relevant circumstances and a meaningful election to plead guilty. The dissenting opinion seems to reason that, since it is not contended that Masthers was legally “insane”, his capacity to understand an ordinary explanation and then make a voluntary and knowing election must be measured by the standard of normal intelligence. This is our point of disagreement.
¶113We make special effort and provisions to the end that the deaf litigant or the litigant whose comprehension of the English language is poor shall understand what is transpiring in court and act knowingly. It seems neither fair nor humane to refuse to make an analogous appropriate special effort when it appears that an accused person’s comprehension is substantially impaired because of mental retardation.
¶114In these circumstances it is our proper and constant concern for fair procedure, not any doctrinal aberration, that dictates an evidentiary hearing to determine, in the light of all that is now known about Masthers’ mentality, whether his plea was voluntary and knowing. If it was, that would end the matter. On the other hand, if he should be permitted to withdraw his plea, it should not be too difficult to find someone skilled in working and communicating with the mentally retarded who could and would communicate effectively with him, so that his participation in any further proceedings would be knowing and meaningful.
¶116(dissenting):
¶117From the premise that the defendant Masthers was a man of limited intelligence and education the majority extracts the conclusion that he may have been incompetent to enter a plea of guilty, so that a hearing is necessary to determine his competency. I cannot agree. In my opinion there is nothing in the record to support the inference that Masthers was incompetent or that he did not know exactly what he was doing when he entered his plea.
¶118Indicted with a co-defendant for armed robbery and released on personal recognizance June 2, 1972 the defendant failed to appear for arraignment on June 16, 1972. He was a fugitive from that date until October 3, 1973 when he was arrested on a bench warrant. Meanwhile the co-defendant, who had implicated Masthers, pleaded guilty and was sentenced.
¶119*731On November 26, 1973 Masthers entered the plea of guilty which is in question here. He was committed pursuant to 18 U.S.C. § 4253, the Narcotic Addict Rehabilitation Act, to determine whether he was an addict and likely to be rehabilitated under the NARA program. The NARA staff reported that his addiction was questionable and that he was not likely to be rehabilitated through the NARA program. The report noted that he was “not functioning at an educational, mental or social level of the average person referred to this program”, his I.Q. score being 57 “which would place him in the ‘mentally defective’ category”. An achievement test indicated he was “operating slightly above the second grade level of academic achievement”. Having received this report, together with a presentence report from the probation officer, the District Court on March 28, 1974 sentenced Masthers to be imprisoned for not less than two nor more than six years.
¶120On April 12, 1974 Masthers, through his counsel, filed a “Motion to Vacate Plea of Guilty under 28 United States Code 2255”; and on May 6, 1974 he filed a Motion for Withdrawal of Plea of Guilty under 32(d) Fed.R.Crim.P. The ground of both motions was that subsequent to the plea of guilty counsel became aware of evidence in the reports on the defendant that he had a subnormal I.Q. and was incompetent to stand trial or plead guilty. On May 6,1974 counsel also filed a Motion for Reconsideration and Reduction of the Sentence imposed upon Masthers. The District Court considered the motions together and by memorandum order denied them without hearing. I think the court was right.
¶121This is not a case in which an innocent man because of ignorance, stupidity or overreaching has pleaded guilty to a crime he did not commit. The record discloses that the complaining witness, who was held up at gunpoint, knew Masthers and was therefore able to identify him without difficulty. Masthers freely confessed his guilt to the police, the probation officer and the NARA staff. In his motion to vacate the plea his counsel asserted that Masthers “continually stated that in fact he had committed the offense in question. Additionally, the government witnesses were interviewed prior to the plea of guilty by counsel, and their testimony was definite that the defendant did the act complained of and the defendant stated that the confession was not coerced.” When he entered his plea of guilty his counsel told the court that he had explained the matter to Masthers who was “doing this of his own free will”. In response to questions from the court Masthers acknowledged that he understood his rights, understood the charge against him, which the court explained, and that the government’s oral statement of the facts of the case was accurate. Although the majority thinks it significant that Masthers answered only “Yes Ma’am” to the various questions from the bench I fail to see what more needed to be said; there was no occasion for a speech. Finally, at the time of sentencing Masthers told the court:
I know I have did some bad things, but I haven’t did nothing like this before in my life, but like Mr. Lowy [his counsel] said I don’t have much education, and everybody knows that.
¶122The majority suggests that in this case “matters of reality . . . should be controlling”. I agree. I think the realities in this case are that the defendant understood that he was charged with the armed robbery of the complaining witness, knew he was guilty, and understood that his plea of guilty would subject him to punishment. Any other conclusion from the facts would, I submit, be a masterpiece of naivete.
¶123Since the defendant understood what he was doing the question comes to this: May a guilty man who freely and with the advice of counsel acknowledges his guilt by a plea of guilty avoid the consequences of his plea upon the ground that he is an uneducated dullard? I think the answer must be no.
¶124Until today the law of this circuit has been that evidence of a low intelligence quotient rating is not evidence of a mental defect and certainly does not demonstrate *732incompetency; and we have never accepted the theory of diminished responsibility. McDonald v. United States, 114 U.S.App. D.C. 120, 123, 312 F.2d 847, 850 (1962) en banc; Stewart v. United States, 107 U.S. App.D.C. 159, 165, 275 F.2d 617, 623 (1960) en banc, rev’d on other grounds, 366 U.S. 1, 81 S.Ct. 941, 6 L.Ed.2d 84 (1961). The majority abandons these sound doctrines; for if the defendant’s low intelligence and meager education make him incompetent to plead guilty then perforce he is incompetent to stand trial, and if he should be tried he could successfully raise the defense of incompetence. Thus the majority creates for this circuit a new defense against charges of crime — a lack of responsibility not amounting to insanity. The decision licenses every illiterate moron to violate the law with impunity. I cannot accept such a doctrine. Accordingly I dissent.
¶125On Sua Sponte Motion for Rehearing En Banc
¶126Before BAZELON, Chief Judge, and WRIGHT, McGOWAN, TAMM, LEVEN-THAL, ROBINSON, MacKINNON, ROBB and WILKEY, Circuit Judges.
¶127ORDER
¶129The motion for rehearing en banc initiated by a member of the Court in regular active service is denied, a majority of the Circuit Judges who are in regular active service not having voted in favor of it (Rule 35, Federal Rules of Appellate Procedure).
¶130Statement of Circuit Judge ROBB of reasons for voting for rehearing en banc. Circuit Judges TAMM, MacKINNON and WILKEY concur in this statement.
¶131Statement of Circuit Judge ROBB of Reasons for Voting for Rehearing En Banc
¶132I have voted in favor of the suggestion by one of my colleagues that this case be reheard en banc. In my judgment the majority opinion is an attempt to introduce the defense of diminished responsibility into the criminal law of this circuit. We rejected that concept in Stewart v. United States, 107 U.S.App.D.C. 159, 165, 275 F.2d 617, 623 (1960), en banc, (opinion by Burger, J.) rev’d on other grounds, 366 U.S. 1, 81 S.Ct. 941, 6 L.Ed.2d 84 (1961). If we are now to change the law that action should be taken by the full court, not by way of a panel opinion and its implications.