Appellant Daphne Essex appeals her conviction for possession of heroin with intent to distribute. 21 U.S.C. § 841(a). At the start of the trial, the defense stipulated to proceeding with a jury of 11 if it became necessary to do so. But a full jury heard all the evidence, began deliberations, and adjourned over the weekend. One juror failed to appear on Monday morning and the court — without finding that there was any reason for excusing him, and over defense objection — permitted the 11 remaining jurors to continue deliberations and to return a verdict.
The government admits the defendant objected that it was “not proven necessary” to continue without the juror and that the court overruled said objection. Since there was no finding of any reason that it was “necessary” to proceed with less than a full jury, the denial of the defendant’s right to a unanimous verdict of the 12 jurors constituted (1) an obvious violation of the terms of the stipulation, and (2) a violation of Fed.R.Crim.P. 23(b) and 31(a). Even assuming the error was not properly raised before the district court, we would find this procedure to be a defect affecting appellant’s substantial right and reviewable under the so-called “plain error” rule, Fed.R.Crim.P. 52(b). We accordingly reverse.1
*835I. Facts
Shortly after the jury was selected, a juror who had been stricken peremptorily by the defense was accidentally seated among the 12 jurors. Only one alternate had been selected; the rest of those examined on voir dire had been dismissed. The improper seating was discovered before the trial started, and the following exchange then occurred:
THE COURT: Mr. Goodbread, I understand that the Government is willing to accept alternate No. One in place of No. 12, and that’s agreeable to you, is it?
MR. GOODBREAD [Appellant’s Counsel]: It is, your Honor.
THE COURT: That means we proceed without an alternate and it is understood that in the event we should have anything happen to one of them, they are unable to come, if it is not less than one juror you are willing to proceed with 11?
MR. GOODBREAD: That’s correct, your Honor.
THE COURT: That’s agreeable to your client?
THE DEFENDANT: Yes.
THE COURT: Very well. Is it agreeable to the Government?
MR. O’MALLEY [Government Counsel]: It is agreeable to the Government, your Honor, but this is an issue which, as the court well knows, has been litigated many times.
If we could have a formal waiver from Miss Essex, that is, to indicate that she has been advised that she has an absolute right to have 12 jurors and that if she waives it she waives any right to appeal that issue, and she must be satisfied with a verdict of 11.
THE COURT: Do you understand, Miss Essex, that you are entitled to a jury of 12 and you wouldn’t [sic] certainly have it if we had it. At the moment you are going to have 12.
I am just saying that in the event something should happen to one of them, we don’t have any alternates.
THE DEFENDANT: Yes, Ma’am.
THE COURT: So if something should happen to one, we would proceed with 11. Is that your understanding and you agree to that?
THE DEFENDANT: Yes, Ma’am, I do.
THE COURT: Very well.
(Tr. 42-43) (emphasis added). Thereupon, the previously stricken juror was dismissed and replaced by the sole alternate.
The case proceeded to trial. None of the jurors was excused during the trial phase. The parties rested on a Friday and the jury retired to deliberate. The jurors deliberated until about 6:00 p.m., when they were given the option to continue deliberations during the evening or to return Monday morning. They voted to return on Monday. In excusing them, to return at 9:30 on Monday morning, the Court said to counsel: “It will not be necessary for you to be here at 9:30 on Monday. The clerk will check them in when they are all here and they will continue with their deliberations” (Tr. 394) (emphasis added).
On Monday, only 11 of the 12 jurors appeared at 9:30. Appellant’s counsel, notified of the situation by telephone, immediately objected to allowing the jury to proceed. No record was made of the objection that counsel was called upon to make — by telephone — first to the court’s secretary, and then to the judge personally. The trial judge, over such defense objection, construed appellant’s oral stipulation as sufficient to cover the situation and directed the jury to resume its deliberations with only 11 jurors. So far as the record indicates, the court made no investigation regarding the missing juror and did not determine the reason for the juror’s failure to appear.
A. The Government’s Concession
We are not completely handicapped by a silent record, however, because appellant’s contemporaneous objections are explained in her brief, and the Government in its brief concedes their correctness:
As explained in her brief, appellant’s counsel, who was at an administrative hearing, communicated his objections to *836accepting a verdict from eleven jurors in a telephone conversation with the trial judge. Brief for Appellant at 7-8. The contents of that call are not a part of the record on appeal, but for the purposes of this appeal we credit appellant’s representations that her counsel objected to accepting a verdict of less than twelve jurors. Just before the verdict was returned, appellant’s counsel noted for the record his objection to accepting a verdict from eleven rather than twelve jurors (Tr. 397).
Brief for Government at 7 n. 3 (emphasis added).
The contemporaneous objections “communicated [to] the trial judge,” id., as “explained in [appellant’s] brief” that the government “credits” are set forth in the margin.2 The specific admission by the Government in its brief is important. It concedes that appellant contemporaneously objected “[a]s explained in her brief.” This concession thus admits that counsel objected to the Court’s ruling on the ground that it would deprive appellant of her right that her “conviction [be achieved] by unanimity of those jurors who actually heard and deliberated the case.” The Government’s concession also admits that counsel objected to the court’s proceeding with only 11 jurors on the ground that the stipulation only agreed to 11 jurors “if necessary, ” and “[t]hat turned out not to be necessary” (emphasis added). Appellant also asserted that such procedure was not “proven necessary.” Despite these timely objections, the court ruled that the 11 remaining jurors could continue their deliberations on the ground that there was “no difference” in whether the juror’s absence was proven necessary or not proven necessary. The dissent essentially takes the same position. The 11 jurors returned a unanimous verdict of guilty, and defense counsel again objected to the jury procedure.3 He alluded to the issue again in his motion for new trial.4
*837It does not appear from the record that either appellant or the Government requested the court to try and locate the missing juror — or that the court ever attempted to locate him or determine the reason for his absence. The parties stated at oral argument that, so far as they knew, the reason for the missing juror’s absence was never determined. The transcript does not indicate that the court ever ruled on the objection it took under advisement (Tr. 400-01).
II. The Federal Rules of Criminal Procedure
A. The Rule Requiring a Jury of Twelve.
At the time of trial, Fed.R.Crim.P. 23(b) provided: *838(Emphasis added.)5 The stipulation here was conditional, and comes under the second clause, which contrary to the dissent’s assertions, see Dissent at 853, requires a finding of some just cause that makes it necessary to excuse a juror.
*837Juries shall be of 12 but at any time before verdict the parties may stipulate in writing with the approval of the court that the jury shall consist of any number less than 12 or that a valid verdict may be returned by a jury of less than 12 should the court find it necessary to excuse one or more jurors for any just cause after trial commences.
*838The Rule also expressly required a written waiver, but this was not done. The court and the parties should have complied with the Rule and executed a written waiver. Had they done so, much of our difficulty might have been avoided. But we do not rest our reversal on the erroneous failure to execute a written waiver. The requirement of a writing is “procedural,” and in situations where the defendant makes an oral waiver in open court with advice of counsel, and where it is clear that the subsequent action taken by the court followed the terms of the waiver, the failure to comply with Rule 23(b) is harmless. United States v. Ricks, 475 F.2d 1326, 1328 (D.C.Cir.1973) (per curiam); United States v. Smith, 523 F.2d 788, 791-92 (5th Cir.1975), cert. denied, 424 U.S. 973, 96 S.Ct. 1475, 47 L.Ed.2d 742 (1976); United States v. Lane, 479 F.2d 1134, 1136 (6th Cir.), cert. denied, 414 U.S. 861, 94 S.Ct. 78, 38 L.Ed.2d 112 (1973). We accordingly rule that the failure to reduce the waiver to writing was harmless error.6
Since a spontaneous oral waiver customarily lacks the clarity, specificity, and assurance of adequate consideration of a written waiver, the circumstances must be examined closely, and must plainly evidence the express and knowledgeable consent of the defendant7 to accepting a verdict of less than 12 jurors.
An examination of the cases in which oral waivers have been held valid is illustrative. In Ricks, the oral waiver at issue was made after the juror did not appear; it is clear that the waiver extended to continuing the trial. The original stipulation agreed to by the defendant in Rogers v. United States, 319 F.2d 5, 7 (7th Cir.1963), cert. denied, 375 U.S. 989, 84 S.Ct. 524, 11 L.Ed.2d 475 (1964), was unambiguous, and was renewed after the juror failed to ap*839pear. Similarly, in Lane the waiver was made after the juror was excused. This is not to imply that only an oral waiver after the juror is excused is valid,8 but in each of these eases it was clear that the defense had intelligently and knowledgeably consented to continuing the trial with 11 jurors under the conditions that necessitated that departure from prescribed procedure.
The stipulation in this case is just as clear. One claim asserted by appellant is that the verdict is improper because she had not agreed that the stipulation would apply during jury deliberations. This broad claim is without merit. Appellant unquestionably agreed to accept a verdict of 11 jurors if it became necessary to excuse one juror during deliberations. The stipulation did not distinguish between the different phases of the trial, nor did it purport to specify any time for its expiration. If a juror was properly excused at any time before verdict, the verdict necessarily would be that of 11 jurors, and such a verdict would have been permissible under the terms of the stipulation and the Rules.
But the stipulation was not an agreement to accept a possible jury of 11 under any and all circumstances. The real issue in this case is whether, under the stipulation and the Rules, the court properly continued the jury’s deliberations without the missing juror.9
B. The Effect of the Stipulation
A conditional stipulation, under the second clause of Rule 23(b), that a valid verdict can be returned by a jury of less than 12 requires a finding by the court that it is necessary to excuse the juror for just cause. A stipulation that the trial will continue if something “should happen” to a juror and he is excused because he becomes “ill,” or he is “unable to come” — i.e., this stipulation — is contingent upon the court finding the existence of the occurrence of the specified condition and upon the court’s finding that it is “necessary” to excuse the juror.
The Advisory Committee Notes which accompanied Rule 23(b) in its original form made clear the types of situations in which jurors should be excused: the Rule is “useful in case it becomes necessary during the trial to excuse a juror owing to illness or for some other cause.” Id. (emphasis added). After the 1977 amendment, the Notes explain that the Rule “makes it clear that the parties ... may enter into an agreement to have the case decided by less than 12 jurors if one or more jurors are unable or disqualified to continue” (emphasis added). The terms “unable” or “disqualified” define what is intended by the term “just cause.” The Rule permits verdicts of less than 12 if (1) it is necessary to excuse a juror for just cause, and (2) there is a stipulation. The terms of the stipulation itself recognized this fact.
Rule 23(b) stipulations thus are contingent upon satisfying this condition precedent. The judge’s statements that formed the basis of the stipulation provided that appellant would be “willing to proceed with 11” jurors “in the event we should have anything happen to them, they are unable to come” (Tr. 43). Thereafter, the judge repeated the condition that the waiver would operate “if something should happen” to one of the jurors. Id. The stipulation thus would not become operative unless a juror’s absence was due to some ascertainable happening that rendered him “unable” or “disqualified” to participate. *840A juror who takes “French leave” 10 cannot be said to have had anything “happen” to him. The waiver, by its terms, did not abrogate either the trial court’s duty to investigate the non-appearance of a juror and make a finding as to the cause, or appellant’s right, in the absence of determined good cause, to the unanimous verdict of all the jurors who heard the evidence, were instructed by the Court, and retired to deliberate on the verdict.11 Because no finding of just cause was made, the stipulation was not complied with, and therefore cannot excuse the violations discussed below.
C. The Rule Requiring a Unanimous Verdict
Rule 31(a) of the Federal Rules of Criminal Procedure requires: “The verdict shall be unanimous.” As indicated above, 12 jurors began deliberations and the verdict was returned by only 11 jurors. There is nothing in the transcript between the recess of the jury of 12 at 6:05 p.m. on Friday, November 19, 1983 (Tr. 395), and the return of the verdict of 11 at 11:22 a.m. on Monday, November 22, 1983 (Tr. 397)— much less any finding of a justifiable reason for accepting the verdict of 11 jurors. And, as noted above, the Government admits that defense counsel objected to the court’s permitting the jury to continue its deliberations with only 11 jurors on the ground “the Government should be required to convince all of the jurors it had attempted to persuade ... twelve in this case” (R. 19-5). While appellant’s objections were not precisely articulated, the substance of her objection made it clear that she did not waive her right to a unanimous verdict. The waiver went to the number of jurors, not to the requirement of unanimity. She had stipulated to the waiver of one juror — but since it had not been found necessary to excuse any juror, that waiver could not be construed as a waiver of unanimity. There is a well recognized distinction between the waiver of a jury of 12, and the waiver of unanimity. United States v. Pachay, 711 F.2d 488, 492 (2d Cir.1983); United States v. Vega, 447 F.2d 698, 701 (2d Cir.1971) (counsel was willing to accept a jury of 11, but would not accept a non-unanimous verdict; hold-out juror excused), cert. denied, 404 U.S. 1038, 92 S.Ct. 712, 30 L.Ed.2d 730 (1972).
Excusing a juror during deliberations jeopardizes the right to unanimity protected by Rule 31(a). This Rule was designed to protect the rights of defendants under the Sixth Amendment to the United States Constitution. See Fed.R.Crim.P. 23, Notes of Advisory Committee subd. (a). When the juror has been excused on a finding of just cause and the defendant has consented, the dangers are minimized and the procedure permitted by Rule 23(b) does not violate Rule 31(a). But when, as here, there is no finding by the court that it is “necessary ... for just cause” to excuse a juror during deliberations, a defendant is denied the right to a unanimous jury verdict that is protected by Rule 31(a). Significantly, four circuits — the Second, Third, Sixth, and Ninth — have held that the intent of the drafters of Rule 31(a) not to permit waiver of unanimity, even with the consent of the defendant, is evident from the preparatory history of the Rule. See United States v. Pachay, 711 F.2d 488, 490-91 (2d Cir.1983) (citing United States v. Lopez, 581 F.2d 1338, 1341-42 (9th Cir.1978); United States v. Scalzitti, 578 F.2d 507, 510-12 (3d Cir.1978); Hibdon v. United States, 204 F.2d 834 (6th Cir.1953); 8A Moore’s Federal Practice ¶ 31.02[1], at 31-3 (2d ed. 1982); 3 C. Wright, Federal Practice and Procedure § 511, at 3-5 (2d ed. 1982)). The dissent completely ignores this feature of the Rule.
*841However, because appellant’s stipulation did not purport to waive the unanimity requirement, and appellant never consented to such waiver, it is not necessary in this case to rely on these authorities. The right to a unanimous jury is derived from the federal rules and the Sixth Amendment. United States v. Morris, 612 F.2d 483, 488-89 (10th Cir.1979); United States v. Scalzitti, 578 F.2d 507, 511 (3d Cir.1978); United States v. Gipson, 553 F.2d 453, 456 (5th Cir.1977). In Apodaca v. Oregon, 406 U.S. 404, 92 S.Ct. 1628, 32 L.Ed.2d 184 (1972), and Johnson v. Louisiana, 406 U.S. 356, 92 S.Ct. 1620, 32 L.Ed.2d 152 (1972), five justices were in agreement that in federal criminal cases juries were required by the Sixth Amendment to be unanimous. Appellant’s counsel, before the jury returned its verdict, several times objected to construing her stipulation as a waiver of unanimity (Tr. 397; R. 19-5 to 19-7). In fact, he expressly pointed out that the verdict would lack “unanimity” (R. 19-6, Brief for Appellant at 6-8). That is sufficient to support her claim of error. This objection is also repeated in her appeal. Brief for Appellant at 6-8, 10-18, 20-30.12
As the Ninth Circuit has explained,
The dynamics of the jury process are such that often only one or two members express doubt as to a view held by a majority at the outset of deliberations. A rule which insists on unanimity furthers the deliberative process by requiring the minority view to be examined and, if possible, accepted or rejected by the entire jury. The requirement of jury unanimity thus has a precise effect on the fact-finding process, one which gives particular significance and conclusiveness to the jury’s verdict.
United States v. Lopez, 581 F.2d 1338, 1341 (9th Cir.1978). This reasoning applies with equal force to a situation where, as here, a juror has absented himself for no valid reason: in both cases there is a danger that dissenting views may not be heard, debated, and resolved by the process of arriving at a unanimous verdict. The requirement of unanimity for a verdict in a criminal case “is inextricably interwoven with” the standard of proof beyond a reasonable doubt. Hibdon v. United States, 204 F.2d 834, 838 (6th Cir.1953) (“there cannot be a verdict supported by proof beyond a reasonable doubt if one or more jurors remain reasonably in doubt as to guilt”). The requirement of unanimity would lose a great deal of its force if, as the dissent implies, jurors may opt out at will. Permitting this erosion would lessen the prosecution’s burden of convincing the entire membership of the jury. The record here cannot support a conclusion that appellant waived her right to a unanimous verdict. We accordingly rule that her right to a unanimous jury verdict was violated.
D. The Verdict of 11 Jurors
Was “it necessary to excuse one ... juror[] for any just cause,” in accordance with the condition of the stipulation or the Rule? While counsel, contrary to the statement of the dissent, did object promptly by telephone to continuing delib*842erations with only eleven jurors, there is no indication that in his telephone call he requested a search or inquiry for the missing juror — or even that he was informed that such inquiry had not been made. But it was the court’s clear duty to determine the whereabouts of the missing juror and make a finding that there was just cause for excusing him. The explanation in appellant’s brief credited by the Government, the statements of the Government prosecutor, and the emptiness of the record cannot support a statement that the reason for the juror’s absence was ever determined —and there is no support whatsoever for the suggestion that the court ever made a finding that just cause existed to excuse the missing juror.
The objections made by appellant were broad enough to raise the issue that the court erred by failing to find “just cause.” Counsel did not, and he was not required to, use those precise words. The objection was to the substantial variance from normal jury procedure in criminal trials that the court indicated it proposed to follow without a finding that such ruling was “necessary.” No magic words are required to constitute an objection. By analogy to objections to evidence, the objection to procedure, the specific ground for the objection being apparent from the context, was sufficient: “(1) a substantial right [was] affected, and (2) the nature of the error was called to the attention of the judge, so as to alert [her] to the proper course of action.” Fed.R.Evid. 103(a), Notes of Advisory Committee subd. (a).
The court considered it was in a position to rule immediately, and it overruled defendant’s objections by permitting the jury of 11 to proceed with its deliberations. In thus permitting the jury of 11 to proceed and return a verdict, the court treated the stipulation to waive a jury of 12, if necessary, as sufficient to waive a jury of 12 even if not necessary. Defendant’s objection was timely, positive, and specific, and the error was clear and obvious. Both objections were again raised in open court before the jury returned (Tr. 397), and in haec verba in defendant’s motions for a mistrial or new trial (R. 19-5b, ¶¶ 16-17). There is nothing to the dissent’s assertion that the substance of the objection was not raised at trial. Dissent at 846, 847, 848, 850, 853. A finding of good cause necessity was required to avoid a violation of Rule 23(b) and no such finding was ever made.
Since (1) the record is silent, and (2) the court must “find” just cause on the record, and (3) the case must be affirmed or reversed on the record, and (4) there is nothing in the record to support the court’s action, the case must be reversed. The stipulation was the only possible basis for proceeding without 12 jurors, and nothing in the record supports a finding that the terms of the stipulation were complied with. Contrary to the implication of the dissent, there is nothing novel about deciding cases on the record or the absence thereof.13 The record in a criminal case must support the judgment, and the court is just as responsible as counsel for seeing *843that the record supports its rulings. The absence of the required finding in the record is a substantial error. The argument that the judge is not ordinarily required to establish the cause for the juror’s absence, see Dissent at 854 n. 42, flies directly in the face of Rule 23(b).
We cannot condone the loose jury practices in which the dissent finds no error. The dissent rests on loose and highly speculative possibilities and assumptions that have no support in the record.14 We find that the court denied defendant her right to the unanimous verdict of 12 jurors without any finding that anything did “happen” to any one of them so that he was “unable” to participate. That is violating the stipulation, not relying upon it. Such trial conduct also violated Rules 23(b) and 31(a).15
IV. Defects Affecting Substantial Rights and Plain Error
From the foregoing it is sufficiently clear that appellant’s basic contentions were in substance made timely and contemporaneously at trial, and the Government so admits. But even assuming that counsel did not specifically ground his objection to the procedure and verdict in the formal terminology of Rule 23(b) or 31(a), or that, as the dissent argues, the objections suffered from other defects, the error was serious enough to require reversal. Fed.R. Crim.P. 52(b) provides:
Plain errors or defects affecting substantial rights may be noticed although they were not brought to the attention of the court.
(Emphasis added.) In United States v. Atkinson, 297 U.S. 157, 160, 56 S.Ct. 391, 392, 80 L.Ed. 555 (1936), the Supreme Court described “plain errors” as follows:
In exceptional circumstances, especially in criminal eases, appellate courts, in the public interest, may, of their own motion, notice errors to which no exception has been taken, if the errors are obvious, or if they otherwise seriously affect the fairness, integrity or public reputation of judicial proceedings.
Thus, under the Rule, an appellate court may ground its decision on defects affecting substantial rights — or plain errors— even though the defect or error was not raised at all. In fact, the rule is frequently applied when the error or defect is not brought to the attention of the trial court. See, e.g., Silber v. United States, 370 U.S. 717, 718, 82 S.Ct. 1287, 1288, 8 L.Ed.2d 798 (1962) (per curiam); Brotherhood of Carpenters v. United States, 330 U.S. 395, 412, 67 S.Ct. 775, 784, 91 L.Ed. 973 (1947); Brasfield v. United States, 272 U.S. 448, 450, 47 S.Ct. 135, 136, 71 L.Ed. 345 (1926); Mahler v. Eby, 264 U.S. 32, 45, 44 S.Ct. 283, 288, 68 L.Ed. 549 (1924).
Plain error has been variously defined, and it depends upon the facts of each particular case. The words “plain error” are self-explanatory to a certain extent, and include “defects affecting substantial rights.” Fed.R.Crim.P. 52(b). The dissent fails to recognize fully this basic feature of the Rule.
The Fifth Circuit defined the circumstances in which plain errors would be noticed as “those involving serious deficiencies which affect the fairness, integrity or *844public reputation of the judicial proceedings or which constitute obvious error.” United States v. Brown, 548 F.2d 1194, 1207 (5th Cir.1977). We defined it in similar terms in United States v. McCord, 509 F.2d 334 (D.C.Cir.1974) (en banc), cert. denied, 421 U.S. 930, 95 S.Ct. 1656, 44 L.Ed.2d 87 (1975):
[T]he doctrine of plain error encompasses those errors which are obvious, affect the substantial rights of the accused and if uncorrected would be an affront to the integrity and reputation of judicial proceedings.
Id. at 341 n. 10 (citing Silber v. United States, 370 U.S. 717, 718, 82 S.Ct. 1287, 1288, 8 L.Ed.2d 798 (1962); Johnson v. United States, 318 U.S. 189, 199-201, 63 S.Ct. 549, 554-55, 87 L.Ed. 704 (1943); United States v. Atkinson, 297 U.S. 157, 160, 56 S.Ct. 391, 392, 80 L.Ed. 555 (1936)). Other definitions: “Plain error is one so clearly prejudicial to substantial rights as to jeopardize the very fairness and integrity of the trial.” Rink v. United States, 388 A.2d 52, 56 (D.C.App.1978). And plain error is that which “affected [appellant’s] ‘substantial rights’ resulting in a miscarriage of justice.” West v. United States, 359 F.2d 50, 53 (8th Cir.), cert. denied, 385 U.S. 867, 87 S.Ct. 131, 17 L.Ed.2d 94 (1966).
The application of the plain error rule is within the sound discretion of the court. Billeci v. United States, 290 F.2d 628, 629 (9th Cir.1961). It is to be applied sparingly to errors vital to defendants. United States v. Frady, 456 U.S. 152, 163 n. 3, 102 S.Ct. 1584, 1589 n. 3, 71 L.Ed.2d 816 (1982) (citing Wiborg v. United States, 163 U.S. 632, 658, 16 S.Ct. 1127, 1137, 41 L.Ed. 289 (1896)).
As noted previously, federal defendants are entitled to (1) juries of 12, unless they are properly waived in accordance with Rule 23(b), and (2) unanimous verdicts by the jurors who deliberated, unless a juror was properly excused in accordance with Rule 23(b).16 Rule 23(b) requires a finding of just cause before it is operable.
A. The Right Affected
The obvious and substantial right of appellant that was denied is her right to a unanimous verdict by the jury of 12 who heard her case and began their deliberations. There is nothing in this trial record, or in the contentions of the Government, that indicates the juror in this case had anything happen to him that gave him any justifiable reason to absent himself. Appellant speculates that the juror may have been a lone holdout for innocence in the face of a hostile pro-conviction majority, and for that reason stayed home rather than take part in the proceedings. There is no evidence that such was the case — there is no evidence of any reason whatsoever— but that is exactly one of the possibilities the Rules are designed to avoid. The defendant’s right to a jury trial, with all its historic and procedural protections, is too important to allow jurors to opt out by simply failing to show up after the commencement of deliberations. The rights of both the defendant and the prosecution under the Rule and the stipulation require that a reasonable investigation be made and the court find it to be neces*845sary for some stated reason constituting good cause to excuse the juror.
The trial court has a great deal of discretion in deciding to excuse a juror for cause. An appellate court ordinarily will not second-guess such a determination, but the parties agree that, to the best of their knowledge, no determination of any reason for the juror’s absence was made in this case. We have demonstrated that this failure violated (1) the stipulation, (2) Federal Rules 23(b) and 31(a), and (3) basic obligations of the court to supervise the jury. Such failures constituted defects which denied appellant’s substantial right, in the absence of determined good cause, to the unanimous verdict of the 12 jurors to whom the determination of the cause was duly submitted.
B. Prejudice
The claim is made by the dissent that appellant has shown no prejudice. But no further prejudice need be shown than that the court did not comply with the stipulation and Rule 23(b), and that appellant was denied her right to have her case decided by the unanimous verdict of the 12 jurors who heard the case. In cases involving secret jury deliberations it is virtually impossible for a defendant to demonstrate actual prejudice. Courts therefore have determined that the potential for serious harm and the interest of the defendant— and the public — in fair, unbiased and secret deliberations are so great that no evidentiary showing of actual prejudice, or of defense counsel’s objection to the internal functioning of the jury of which he could not possibly be informed, is required.
For example: Without regard to actual prejudice, it has been held to constitute error for a trial court to permit a prosecution witness merely to enter the jury room during deliberations in order to play a tape for the jurors, United States v. Pittman, 449 F.2d 1284, 1286 (1971); or to place the jury in the custody of sheriffs’ deputies who are testifying at the trial, even when there is no indication that they have spoken to the jurors, Turner v. Louisiana, 379 U.S. 466, 472-74, 85 S.Ct. 546, 549-50, 13 L.Ed.2d 424 (1965). It is plain error for the trial judge to call the jury back from deliberations and ask them how they are numerically divided, even when there is no showing that it had any influence on the jury. See Brasfield v. United States, 272 U.S. 448, 450, 47 S.Ct. 135, 136, 71 L.Ed. 345 (1926) (“We deem it essential to the fair and impartial conduct of the trial that the inquiry itself should be regarded as grounds for reversal.”); Government of the Virgin Islands v. Romain, 600 F.2d 435, 437 (3d Cir.1979); United States v. Noah, 594 F.2d 1303, 1304 (9th Cir.1979) (per curiam). Similarly, it is plain error for the trial court to permit an alternate juror to retire to the jury room for deliberations with the other jurors, even for a period of as little as 45 minutes and even when the alternate says nothing. See United States v. Chatman, 584 F.2d 1358, 1361 (4th Cir.1978) (although evidence against defendant was overwhelming, reversal was required). We believe that prejudice is inherent when a court permits a jury of 12 to continue deliberations and return a verdict with only 11 jurors, without making the finding required by the Rule and the stipulation. The dissent can cite no decision that supports excusing a juror (except in accordance with a contemporaneous agreement) without a finding of a stated reason.
Underlying the dissent’s plain error analysis is the apparent notion that the Rule cannot be applied because it asserts that no “miscarriage of justice” occurred in this case. But where, as here, the prejudice is inherent in the error complained of, the defendant is not required to prove that he is innocent, or that the outcome of the trial would have been different, had the error not been made. Brasfield, supra, 272 U.S. at 450, 47 S.Ct. at 136. Chatman, supra, 584 F.2d at 1361. The evidence amassed against appellant was considerable — but it is well settled that even defendants who are obviously guilty are entitled to the basic procedural safeguards of a fair trial. See, e.g., Brewer v. Williams, 430 U.S. 387, 406, 97 S.Ct. 1232, 1243, 51 L.Ed.2d 424 (1977) (right to counsel during non-coercive questioning); Estes v. Texas, 381 U.S. 532, 542-44, 85 S.Ct. 1628, 1632-33, 14 L.Ed.2d 543 (1965) (broadcast of trial *846jeopardized fairness); In re Murchison, 349 U.S. 133, 137-38, 75 S.Ct. 623, 625-26, 99 L.Ed. 942 (1955) (judge who functions as “one-man grand jury” cannot preside at contempt trial arising from grand jury proceedings); Rideau v. Louisiana, 373 U.S. 723, 726-27, 83 S.Ct. 1417, 1419, 10 L.Ed.2d 663 (television broadcast of defendant’s confession).
In our judgment, as outlined above, the defects affected appellant’s substantial rights, and thus justify reversal under Rule 52(b). We disagree with the dissent that this court is powerless to correct errors of such magnitude.
The judgment of the trial court is reversed, and a new trial ordered.17
Judgment accordingly.
The abbreviation "Tr." refers to the transcript; “R.,” to the Court’s record file; and to the Joint Appendix.
. Contrary to the assertion of the dissent, our holding in this case cannot be considered any change in the law. As this opinion explains, infra, the dissent consistently ignores (1) the provision of the stipulation that the waiver of the 12-person jury was conditional on something happening to a juror, (2) the fact that there was a complete absence of any “finding" by the court, and (3) that part of Rule 52(b) (the so-called plain error rule) that "defects affecting substantial rights may be noticed although they were not brought to the attention of the court.”
. The Court’s secretary stated [to defense counsel on the telephone] that she was informed by the Court that it was understood that the Defendant had no objection to proceeding with only eleven jurors.
Counsel [for defendant] then informed Chambers that such was not the understanding or the agreement. Rather, what the Defendant had agreed to was to proceed to trial, if necessary, with eleven jurors. That turned out not to be necessary, since the case had been heard for two days by twelve jurors, all of whom had retired and invested nearly two hours of deliberation in the case. Counsel expressed opposition to proceeding with eleven jurors under these changed and different circumstances, stating the opinion that the Government should be required to convince all of the jurors it had attempted to persuade (however many that may have been — twelve in this case, as usual) and that to allow the panel to be whittled away by exigencies and circumstances would geometrically lighten the Government's burden to achieve conviction by unanimity of those jurors who actually heard and deliberated the case. [This is a plain objection to lack of unanimity.] Counsel further expressed the opinion that the agreement concerning and the matter of the alternate juror was academic and moot at that point, since the alternate juror would have been excused before the jury had retired to begin its deliberations anyway, and would have had no part to play had a juror failed to appear to resume deliberations. On those grounds, Counsel objected to proceeding with only eleven jurors after deliberations had begun. [This separate objection was based on counsel’s construction of the stipulation.]
In counsel's subsequent [continuation of the telephone] conversation with [the judge], he repeated the foregoing contentions and expressed further opposition to the case proceeding without the twelfth juror present. [The judge] took the position at that point, however, that Counsel and Defendant had earlier agreed on the record to proceed with only eleven jurors. [This abbreviated description of the stipulation ignored the pre-conditions for a jury of 11.] When informed of Counsel’s distinction between an earlier stated agreement to proceed to trial (if proven necessary) with eleven jurors and a subsequent requested agreement to allow only eleven of the twelve who had heard the case to then decide it (not proven necessary), [the judge] expressed the opinion that there was no difference in the fact situations. Stating that she did not know any other way to proceed, [the judge] then informed Counsel that she would allow the eleven jurors to proceed with deliberating the case. Counsel restated his position on the phone and requested [the judge’s] understanding. (R. 19-6).
Brief for Appellant at 6-8 (emphasis added).
. When the jury was ready to return a verdict at 11:22 a.m. on Monday morning, defense counsel entered the following objection:
THE COURT: You may bring in the jury.
*837MR. GOODBREAD: Your Honor, before we bring in the jury, may I enter into the record my understanding of the 11-juror situation?
THE COURT: Surely.
MR. GOODBREAD: I haven't inquired of the Government what his position is.
For the Record, the Defense understanding on the agreement to proceed with 11 jurors was, on the first day of the trial, when we used up the alternate, if the full 12 did not return the next day, we would proceed through trial with 11 jurors.
The record shows all 12 did show up, all 12 did hear the case.
My understanding is the court dutifully informed me, by telephone, this morning only 11 showed up for the resumed deliberations.
It was not the defense’s understanding that we would agree to go forward with only 11 jurors during the deliberations.
I just wanted to enter that on the record, if the court please.
THE COURT: Very well.
[The jury then returned with a verdict of guilty.]
MR. GOODBREAD: If it please the court, we would have two motions.
We would ask for a mistrial on the ground that an insufficient panel was present, after 12 jurors had retired, as we placed on the record earlier.
The record will show only 11 jurors present and that’s clearly improper judicial proceedings in a situation of this nature.
It’s our position that the excusing of the alternate would have taken place before the jurors retired, at any rate, and that 12 would have — or whatever number would have — been present on that occasion would have been required.
On that occasion, 12 retired and, as the record shows, only 11 returned with the verdict and we would ask for a mistrial based on that insufficiency. [This is a plain objection to lack of unanimity.]
Does the court wish me—
THE COURT: I was just waiting for the Government to respond.
MR. O’MALLEY: Your Honor, there was clearly an inquiry by this court as to whether or not the defendant would waive the right to be present with 12 jurors.
There was never any qualification on that request for a waiver, never any inquiry by the court whether that waiver was limited only to 12 jurors during trial, never any indication by the defense that that waiver was limited to only 12 jurors — less than 12 jurors during the trial proceedings themselves.
That was a waiver that was clearly made, openly stated, with the advice of counsel, and put on the record.
That waiver being heard and the luck of the draw or the will of the jury having gone against the defendant, I think it’s improper at this time for this motion and I think this motion should be denied.
THE COURT: The Court will take it under advisement.
(Tr. 397, 400-01) (emphasis added).
. Appellant’s motion for new trial complained about the haste with which deliberations were resumed, stating: "The delay of another day for a bench warrant search for the missing juror (or for time to allow him to recuperate, if ill) ... would have been preferable to the sua sponte ascription of waiver in the prior agreement to proceed to trial with eleven jurors, if necessary, and the order of the Court that the jury immediately renew their deliberations with only eleven jurors present.” Defendant’s Memorandum in Support of Motion for New Trial, at 6 n. 4 (R. 19) (emphasis added). This argument presumably would have evoked a contradiction if the court had ascertained the reasons for the juror’s absence.
. The Supreme Court has subsequently promulgated a new rule, which became effective August 1, 1983:
Juries shall be of 12 but at any time before verdict the parties may stipulate in writing with the approval of the court that the jury shall consist of any number less than 12 or that a valid verdict may be returned by a jury of less than 12 should the court find it necessary to excuse one or more jurors for any just cause after trial commences. Even absent such stipulation, if the court finds it necessary to excuse a furor for just cause after the jury has retired to consider its verdict, in the discretion of the court a valid verdict may be returned by the remaining 11 jurors.
51 U.S.L.W. 4507, 4509 (U.S. May 3, 1983). The new Rule adds the italicized language. Both the prior Rule and the amended Rule require a finding by the court.
. Our ruling on this point does not indicate our approval of this procedure. The prosecutor in this case was well aware of the litigation that has surrounded Rule 23(b). He sought a "formal" waiver from appellant because, he said, the waiver issue “ha[d] been litigated many times” (Tr. 42). The prosecutor obviously was aware of the requirements of 23(b), since he was aware of cases construing it. But neither he, defense counsel, nor the court made any attempt to get a written waiver, as the rule explicitly requires. There was no reason not to put the waiver in writing. While the rule primarily protects the defendant, it also protects the public. Even rules which are "only procedural," Ricks, supra, 475 F.2d at 1328, are not meant to be ignored. The reluctance of an appellate court to overturn a conviction on some procedural violations should not be mistaken for a license to disregard the Federal Rules of Criminal Procedure.
. Since the oral waiver in this case was made by the defendant and her counsel, it is not necessary to address the question whether a stipulation made by counsel, without the defendant’s express consent, would be sufficient. The issue has divided other circuits. Compare United States v. Guerrero-Peralta, 446 F.2d 876, 877 (9th Cir.1971) (agreement by counsel in defendant's presence ineffective; express statement by defendant required), with United States v. Spiegel, 604 F.2d 961, 965 (5th Cir.1979), cert. denied, 446 U.S. 935, 100 S.Ct. 2151, 64 L.Ed.2d 787 (1980) (the rule uses term "parties,” not "defendant,” and thus counsel may waive right). The waiver in this case clearly was made "competently, intelligently, and understanding^” by appellant, “with a full understanding of the implications thereof," and the condition upon which it was premised. Cf. Davis v. United States, 123 F.Supp. 407, 414 (D.Minn.1954), aff’d, 226 F.2d 834 (8th Cir.1955), cert. denied, 351 U.S. 912, 76 S.Ct. 702, 100 L.Ed. 1446 (1956).
. In cases involving written waivers permitting eleven jurors, it has been held that a pretrial stipulation need not be renewed at the time the juror is excused, even if the juror is excused during deliberations. See United States v. Pacente, 503 F.2d 543, 552 (7th Cir.), cert. denied, 419 U.S. 1048, 95 S.Ct. 623, 42 L.Ed.2d 642 (1974); United States v. Stolarz, 550 F.2d 488, 493 (9th Cir.), cert. denied, 434 U.S. 851, 98 S.Ct. 162, 54 L.Ed.2d 119 (1977). That is the position taken in the Advisory Notes accompanying the 1977 Amendment to Rule 23(b).
. There is nothing in the transcript to indicate that the court ever "excused” the juror. The court just permitted the jury of 11 to proceed with its deliberations.
. “French, leave. Leaving a party, house, or neighborhood without bidding good-bye to anyone; to slip away unnoticed." E. Brewer, The Dictionary of Phrase and Fable (1978).
. Since this stipulation did not even purport to waive the trial court’s just cause determination, there is no need to decide whether this duty can ever be waived. Cf. Fowler v. Hunter, 164 F.2d 668 (10th Cir.1947), cert. denied, 333 U.S. 868, 68 S.Ct. 785, 92 L.Ed. 1146 (1948) (waiver entered into in habeas corpus case after jurors did not return from a break; no reason given for absence).
. The following points in appellant’s brief clearly indicate her objection to construing her stipulation as a waiver of unanimity:
I. APPELLANT WAS DENIED HER FIFTH AND SIXTH AMENDMENT RIGHTS TO DUE PROCESS AND A FAIR TRIAL BY THE TRIAL COURT’S RULING THAT FEWER THAN THE TWELVE ORIGINAL JURORS WHO HEARD THE CASE COULD RETURN A VERDICTf.]
II. THE DEFENDANT AGREED ONLY TO PROCEED TO TRIAL WITH FEWER THAN TWELVE JURORS, IF NECESSARY. THAT CONTINGENCY NEVER AROSE AND THE WAIVER IS THEREFORE MOOT[.]
IV. CONSEQUENTLY THE RETURN OF A GUILTY VERDICT BY FEWER THAN THE TOTAL NUMBER OF JURORS WHO HEARD AND UNDERTOOK TO DECIDE THE CASE DEPRIVED DEFENDANT OF DUE PROCESS OF LAW AND A FAIR TRIAL[.]
Brief for Appellant at ii (emphasis added). The brief also relies upon Rule 23(b), and the Conclusion asserts that she was denied her rights under the 5th and 6th Amendments:
The Defendant has been deprived of her right under the United States Constitution to due process of law and to a fair trial, pursuant to the Fifth and Sixth Amendments thereof, and the judgment of the District Court should be reversed and a new trial ordered.
. With no supporting claim by the Government, and with no support in the record, the speculation by the dissent that the judge might have "had just cause for dismissing the juror,” Dissent at 849, is bootless. Nothing in the record indicates that the court ever dismissed the juror, much less excused him. So far as the record is concerned, the court just permitted the jury of 11 to continue its deliberations without the twelfth juror and without making any finding.
Describing the record as "incomplete,” Dissent at 850, is a misstatement. The record is complete — it just does not show something that never happened. It does not support a finding that the court acted in compliance with the stipulation because it did not so act. The record does not reflect that the required inquiry was ever made, and also, by its silence reflects that the required finding was never made.
The dissent says we "cannot say what the judge here did.” Dissent at 857. That is incorrect. The record indicates that the court directed continuing deliberations with only 11 jurors in a criminal case submitted to 12 jurors, without complying with the terms of the stipulation upon which the court was required to ground its action. To assume in a criminal case, when the record is silent, that the court properly applied a rule when a specific finding is required and the record discloses none, cannot be justified.
. See Dissent at 849 ("might have been”), 853 (“it is at least arguable"); 854 n. 42 ("it is entirely possible”), 857 (“for all we know,” twice), 857 n. 51 ("might well have been”), and 858 (“The judge apparently assumed”).
. One error in the dissent is its insistence on treating the stipulation as though the waiver was not conditional. To assert that the "court relied on the defendant’s stipulation,” Dissent at 19, is a plain misstatement. It only relied on the waiver portion of the stipulation and ignored the express limited preconditions which were required to be proven before the waiver could be applied. Treating the court’s error here as minimal would trivialize the rights of federal defendants to a jury trial as required by the Constitution, the Federal Rules of Criminal Procedure, and federal court decisions.
To say that the court gave the defendant the "benefit of her bargain” is a perversion of both “benefit” and “bargain.” Dissent at 855. Some bargain — continuing a trial with an incomplete jury without giving any reason and denying the defendant a unanimous verdict of the jury to whom the case was submitted.
. The Government argues that its contrary position here is "completely supported” by United States v. Pacente, 503 F.2d 543 (7th Cir.), cert. denied, 419 U.S. 1048, 95 S.Ct. 623, 42 L.Ed.2d 642 (1974). Brief for Government at 9, 11. Nothing could be further from the truth. In Pacente, the defense stipulated in writing to excusing one juror "by reason of illness or for any other good cause as determined by the Court.” In accordance with the stipulation the court excused one juror during its deliberations for "good cause," i.e., her "father [became] seriously ill and not expected to live.” The judge in open court announced his finding of facts which made it necessary to excuse the juror and the court of appeals held that the facts constituted “good cause." Id., at 551-53. In sum, the court in Pacente complied with the conditions of the stipulation and set forth its finding of "good cause” on the record. In contrast, the court here made no finding of any reason whatsoever to show that it was "necessary,” as the stipulation and the Rule both required, to proceed without the absent juror. In passing, it should be recognized that this requirement for a unanimous verdict of 12 jurors, except when just cause is shown, protects both an acquittal minority and a guilty minority.
. The dissent indulges in many misstatements of fact and law, extreme prophecy, overstatements, and extravagant exaggeration. It repeatedly understates the extent of the objections that were raised by defense counsel. It completely ignores both the plain implication of the issues raised by the timely objections and the court’s authority under Rule 52(b). These errors are generally answered by the statements of fact and law set forth above, but a few deserve additional comment.
It should be noted that, since the judge had started the trial of another case when the Essex jury retired to deliberate, taking a short time to have the juror’s absence checked by the marshal would not have delayed the subsequent trial. Meanwhile, as the Essex jury was in the deliberating phase, the court easily could have suspended jury deliberations to await the marshal's report on the absent juror without holding up the other trial.
It is also a misstatement to assert that we are granting the mistrial merely because of an 11-juror verdict. We are reversing because the verdict of 11 was returned without complying with the stipulation, which was the only basis that would justify a verdict of 11 jurors. Under such circumstances the verdict also violated the unanimity requirement of Rule 31(a). The dissent asserts there was a deliberate waiver, but there was never a waiver of the requirement for a "unanimous" verdict of the jurors that heard the case, and that objection was clearly raised. To state that the objection was not raised and understood is to underestimate the perception of the learned and experienced trial judge.
The fact that the stipulation was not limited to the open trial — contrary to the defendant’s contention — is no justification for not applying it to the jury deliberations as the Government contended. The defense made two objections: (1) that the stipulation was limited to the open trial, and (2) that in any event the terms of the stipulation were not complied with. The fact that we ruled against the first point does not justify a refusal to apply our decision that the stipulation did apply to the factual situation covered by the second point.
The dissent denigrates the requirement of a unanimous verdict of the jurors to whom the case was submitted for decision as only a Federal Rule. However, the Federal Rules, and this Rule in particular, have more status than a pure statute, since this Rule originated with the Supreme Court and was "approved" by Congress. See 91 Stat. 320. Rule 23 also has constitutional underpinnings; it "is a formulation of the constitutional guarantee of trial by jury.” Fed.R. Crim.P. 23, Notes of Advisory Committee subd. (a).
The dissent suggests that there is no need for the court to make a record for its ruling. Dissent at 855-856. But Rule 23(b) requires where the stipulation is conditional that "the court find it necessary ....” That is no idle requirement that is satisfied by a silent record. For the dissent to indulge in the shorthand statement that Essex "preferred a verdict of less than 12 to delay or mistrial,” Dissent at 857 n. 52 (emphasis added), it must ignore the controlling fact that her consent was limited to situations where "something happened” to a juror and it was shown to be “necessary” to excuse him. "Preferred” is a gross overstatement and fails to recognize the narrow conditions under which Essex was willing to accept a verdict of 11.
The dissent recognizes that under the present Rule, see note 5 supra, the court should "justify the choice made” — but the stipulation and the prior Rule placed the same requirement on the court, and it must similarly "justify the choice.”
Some objection should also be taken to the essence of the dissent’s contentions: that appellant should be penalized because her counsel, with no prior notice, did not set forth all his objections in precise formal terms immediately upon being informed by telephone that one jur- or was missing. The dissent fails to recognize that nothing in the record indicates that appellant’s counsel was advised at any time that the court had not found that something “happened” to the missing juror that made it "necessary" to continue without him. Counsel did "object” immediately to the court’s relying on the stipulation to permit a jury of 11 to continue deliberations under the limited facts that were given to him by telephone. We have not yet reached the stage where criminal cases are tried, and defendants’ substantial rights are frittered away by telephone, without any record being made.