join, dissenting.
Beginning with the defendant’s brief and only appearance in Quakertown, Pennsylvania, the Government’s case against him is built upon speculative inferences, legal fiction, and double hearsay. These are joined by the fragile tissue of a judicial presumption that, once a defendant has been found to have participated in a conspiracy, he is presumed to continue to participate in it despite the lapse of considerable time, unless he produces affirmative evidence that he has withdrawn.
The Government’s case is grounded on meager testimony — barely sufficient under the preponderance, of evidence rule of this circuit — offered as independent evidence of defendant’s participation in the marijuana conspiracy1 as a potential buyer. On the *851basis of this slight, inferential, and dubious evidence the Government introduced the out-of-court hearsay declarations. To accomplish this objective the Government leaned heavily on the coconspirator rule, which is based on the legal fiction that each conspirator is the agent of the other. It has neither produced the declarant for cross-examination nor has it shown that he is unavailable. Also absent is not only direct or circumstantial evidence of guilt, but the procedural opportunity for fairness and the discovery of truth. The accused has been denied the fundamental right to cross-examine the out-of-court declarant. A society that values the good name and liberty of every person should not condemn anyone on such a naked amalgam of double hearsay, legal fiction, and judicial presumption. I therefore dissent.
I.
No one disputes the existence of the 1980 conspiracy among the two Quintiliano brothers and others to smuggle marijuana into Pennsylvania from Colombia, South America, and to distribute it. As the majority correctly observes, op. at 840, the Government prosecuted Gibbs on the theory that he too participated in the conspiracy as the potential purchaser. To prove his participation, the Government established that on April 7, 1980, Gibbs flew to Wings Air Field in Montgomery County, Pennsylvania, where Joseph Quintiliano2 met him. They then traveled to the Quakertown Airport, where they inspected for several minutes the Beechcraft airplane purchased several weeks previously by Quintiliano to smuggle the marijuana from Colombia.
At this point, there may have been several legitimate reasons why Gibbs was in Quakertown. State police officers, however, gave- it a criminal conspiratorial flavor by testifying that they observed Quintiliano, upon leaving the Quakertown Airport, engage in what they considered evasive driving to avoid surveillance.
Based upon this tenuous evidence of Gibbs’s complicity in the conspiracy, the Government introduced out-of-court statements allegedly made by Quintiliano to Bilella and White, unindicted coconspirators, of what Gibbs allegedly told Quintiliano.3 These out-of-court statements, which the majority acknowledges were the principal evidence offered against Gibbs, op. at 841, became the fulcrum of the Government’s case and were essential to convict Gibbs. The Government never called Quintiliano, but instead produced Bilella and White, who testified that about the time Quintiliano purchased the Beechcraft airplane he told them that he planned to sell the imported marijuana to a customer named “Jake.” White testified that Gibbs, whom he had met when Gibbs came to inspect the plane at Quakertown, matched Quintiliano’s description of “Jake” and had identified himself to White under that name.
The crux of the Government’s case depends upon the out-of-court statements made on the evening of October 4, 1980, at Quintiliano’s home. These statements allegedly (op. at 841-842) made by Gibbs alluded to Quintiliano’s reopening of negotiations with him in early October 1980 after Quintiliano had rejected some Florida prospects for the purchase. They were introduced in evidence through Bilella’s and White’s testimony. Quintiliano told them that he had telephoned “Jake” when he rejected the prospective Florida purchasers and that “Jake” told him that he would “try to make the necessary arrangements” for the purchase.
In an effort to give some credence to the hearsay testimony, the Government introduced evidence of certain telephone records. They showed that long distance calls were made early in October 1980 from *852Quintiliano’s residence in Pennsylvania to the Gibbs residence or to the Ram Broadcast Company in Massachusetts. There is no evidence, however, of any conversation with Gibbs. The Government suggests that from this series of telephone calls it can be inferred that Gibbs and Quintiliano were discussing arrangements for the sale of the marijuana in furtherance of whatever plans they had made at their April meeting. There are several major problems with the Government’s argument, however. One obvious difficulty is the absence of evidence directly linking Gibbs with Ram or proof that any of Quintiliano’s calls to Ram were returned. Moreover, except for Quintiliano’s out-of-court hearsay, there is nothing to indicate the substance of the conversations or that they actually conversed.
II.
Although I am inclined to agree with the majority that there may be sufficient evidence to permit a reasonable inference of Gibbs’s initial complicity in the enterprise, I strongly believe that the admission of the double hearsay statements constitutes serious and therefore reversible error because it deprived Gibbs of his sixth amendment right to confrontation. Because the independent evidence upon which the Government relied for introduction of the out-of-court statements was so tenuous,4 it was highly important that any out-of-court statements be unequivocal and that the declarant be subject to searching cross-examination.
In Dutton v. Evans, 400 U.S. 74, 91 S.Ct. 210, 27 L.Ed.2d 213 (1970), the Supreme Court recognized that the confrontation clause and the hearsay rule “stem from the same roots,” but stated that “the Court has never equated the two, and we decline to do so....” Id. at 86, 91 S.Ct. at 218. The confrontation clause issue and the evidentiary question therefore must be separately analyzed, and the sixth amendment may require the exclusion of evidence even though admissible under Fed.R.Evid. 801(d)(2)(E). See United States v. Perez, 658 F.2d 654, 660 & n. 5 (9th Cir.1981). See also United States v. Palumbo, 639 F.2d 123, 131 (3d Cir.) (Adams, J., concurring), cert denied, 454-U.S. 819, 102 S.Ct. 100, 70 L.Ed.2d 90 (1981); United States v. Puco, 476 F.2d 1099, 1102 (2d Cir.), cert. denied, 414 U.S. 844, 94 S.Ct. 106, 38 L.Ed.2d 82 (1973).
In Ohio v. Roberts, 448 U.S. 56, 65-66, 100 S.Ct. 2531, 2538-39, 65 L.Ed.2d 597 (1980), the Supreme Court identified two restrictions that the confrontation clause places on the use of hearsay evidence in criminal trials. First, the prosecution generally must establish that the hearsay evidence is necessary because the declarant is unavailable. Second, the hearsay statement must be reliable. “Reflecting its underlying purpose to augment accuracy in the factfinding process by ensuring the defendapt an effective means to test adverse evidence, the Clause countenances only hearsay marked with such trustworthiness that ‘there is no material departure from the reason of the general rule.’ ” Id. at 65, 100 S.Ct. at 2538 (quoting Snyder v. Massachusetts, 291 U.S. 97, 107, 54 S.Ct. 330, 332-33, 78 L.Ed. 674 (1934)). In the instant case, the necessity aspect of this test has not been met. Therefore, there is *853no need to reach the question whether the reliability prong has been satisfied.
Although the literal language of the sixth amendment guarantees to any accused “the right ... to be confronted with the witnesses against him,” the Supreme Court has recognized the necessity that extrajudicial statements sometimes must be used because of the declarant’s unavailability. Gibbs maintains that Quintiliano was not legally unavailable to testify and that therefore there was no need for introduction of his out-of-court statements. The Government contends that a showing of unavailability is not required.
The Supreme Court discussed the unavailability component of the confrontation clause in Ohio v. Roberts, supra:
[I]n conformance with the Framers’ preference for face-to-face accusation, the Sixth Amendment establishes a rule of necessity. In the usual case ... the prosecution must either produce, or demonstrate the unavailability of, the declarant whose statement it wishes to use against the defendant.
448 U.S. at 65, 100 S.Ct. at 2538. A witness may be deemed “unavailable” only if the prosecution has made “a good faith effort to obtain his presence at trial.” Id. at 74, 100 S.Ct. at 2543 (emphasis in original) (quoting Barber v. Page, 390 U.S. 719, 725, 88 S.Ct. 1318, 1322, 20 L.Ed.2d 255 (1968)). And, under the foregoing language in Ohio v. Roberts, it is the prosecution that must produce or demonstrate the unavailability of the declarants. The Court did not impose any burden on the accused to show that the declarant is available.
Quintiliano was a codefendant in the Government’s prosecution who had pleaded guilty to two of the three counts in the indictment and was still awaiting sentencing at the time of Gibbs’s trial. There is no evidence in the trial record that bears on Quintiliano’s availability. Although Quintiliano was faced with an impending sentencing proceeding and might not have been willing to waive his fifth amendment right and testify against Gibbs, there is a possibility that he would have because he had already pleaded guilty. Because there is nothing in the record to indicate that the Government ever established that Quintiliano would refuse to testify against Gibbs, the Government failed to carry its burden under Ohio v. Roberts, 448 U.S. at 74-75, 100 S.Ct. at 2543-44, to demonstrate the declarant's legal unavailability.
In a footnote, the Roberts Court suggested that “[a] demonstration of unavailability, however, is not always required,” id. at 65 n. 7, 100 S.Ct. at 2538 n. 7. To support this proposition, the Court cited Dutton v. Evans, 400 U.S. 74, 91 S.Ct. 210, 27 L.Ed.2d 213 (1970), in which it had permitted the admission of coconspirator hearsay in circumstances where a seemingly available declarant was not called to testify. The Roberts Court described Dutton as a case where the requirement of unavailability could be dispensed with because “the utility of trial confrontation” would have been “remote.” See 448 U.S. at 65 n. 7, 100 S.Ct. at 2538 n. 7; United States v. Perez, 658 F.2d at 661. Here, Quintiliano’s statements do not fall within the Dutton exception to the unavailability requirement because they are crucial to conviction, and not “of peripheral significance at most,” as in Dutton, 400 U.S. at 87, 91 S.Ct. at 219. Moreover, in Dutton, the Court pointed out that the accused there had full opportunity to cross-examine the declarant as to whether he actually heard the person make the statement offered in evidence.
The instant case is also distinguishable from Dutton because the Government has not carried its burden of showing that Quintiliano’s hearsay statements were “marked with such trustworthiness,” Ohio v. Roberts, 448 U.S. at 65, 100 S.Ct. at 2538, to justify disregarding the unavailability requirement. I can conceive of possible motives Quintiliano might have had to misrepresent Gibbs’s involvement in the crime.5 For example, Quintiliano may have *854misrepresented Gibbs's involvement to reassure his coconspirators that plans for the sale of the contraband were proceeding smoothly. In addition, it is plausible that the statements were contrived as part of Quintiliano’s bargaining strategy. Quintiliano may have seen a chance of pressuring the Florida buyers to offer better terms by giving the impression that he had another buyer waiting in the wings. Under these circumstances, the cross-examination of the testifying witnesses (White and Bilella) could not adequately test the truthfulness of Quintiliano’s statements.
Most important, I believe that the instant case falls outside the Dutton exception to the unavailability requirement because I do not believe Quintiliano's hearsay statements were only “of peripheral significance,” see 400 U.S. at 87, 91 S.Ct. at 219, in the prosecution’s case. The challenged statements provide direct incriminating evidence, in the form of Quintiliano’s declaration that Gibbs had agreed to buy the marijuana. Admittedly, there is some other evidence linking Gibbs to the conspiracy. However, unlike Dutton, where the disputed evidence consisted of a single sentence reported by one of twenty witnesses, the coconspirator hearsay presented in Gibbs’s trial was the core of the Government’s case.6
The opportunity to cross-examine an accuser or a critical witness is a powerful tool in the search for truth and in the assessment of guilt or innocence. The confrontation clause, in the words of the Supreme Court, contemplates
“a personal examination and cross-examination of the witness in which the accused has an opportunity, not only of testing the recollection and sifting the conscience of the witness, but of compelling him to stand face to face with the jury in order that they may look at him, and judge by his demeanor upon the stand and the manner in which he gives his testimony whether he is worthy of belief.”
Ohio v. Roberts, 448 U.S. at 63-64, 100 S.Ct. at 2537-38 (quoting Mattox v. United States, 156 U.S. 237, 242-43, 15 S.Ct. 337 at 399, 39 L.Ed. 409 (1895)). Because the right of confrontation is so important in our adversarial system, it may only be denied in exceptional situations. The Government has not met its burden to show that the instant case is such an exceptional situation. The prosecution has failed to establish either that the declarant cannot be produced for trial or that the hearsay is sufficiently reliable and insignificant to justify dispensing with a showing of unavailability.
The admission of Quintiliano’s statements without giving • the defendant the opportunity to cross-examine the declarant sharply tipped the scales of justice against the defendant. The historic safeguard guaranteeing the accused the right to be confronted with the witnesses against him may not be disregarded.
III.
The majority, however, does not reach the merits of the sixth amendment issue because it asserts that “Gibbs did not pre*855serve that issue for appeal [and therefore] it cannot serve now as a basis to reverse Gibbs’s conviction.” Op. at 847. But the issue was raised in the trial court, perhaps not as specifically or as timely as it might have been, but it was raised sufficiently to be preserved and heard.7
First, the defendant repeatedly objected during the Government’s case in chief to the admission of Quintiliano’s statements on the ground that they failed to satisfy Fed.R.Evid. 801(d)(2)(E). Although these objections did not specifically refer to the sixth amendment issue, they should have sufficed to put the trial judge on notice that intertwined with them was a constitutional issue. See State v. Poole, 31 Or. App. 925, 572 P.2d 320 (1977) (objection only on the ground of hearsay was so closely related to the incompetency of the witness as to preserve for appeal the challenge based on the incompetency of the witness). Second, if there was any doubt concerning notice to the Government and the court, it was resolved when the Government rested without calling Quintiliano or producing proof of his unavailability. Only at that point could Gibbs have been certain that he would be denied his constitutional right to confront his accuser. He therefore moved, while the court, jury, and counsel were still present, to strike the hearsay, stating:
[A]side from the co-conspirator exception to the hearsay rule, there is a clear sixth amendment problem in this case, and the co-conspirator hearsay rule which permits the introduction of co-conspirator hearsay does not subsume and take place of the sixth amendment right to confrontation ... [and] the other cases have recognized that there is still, notwithstanding the existence of 801(d)(2)(E) ... a sixth amendment right of a defendant to confront and cross-examine his accusers.8
(452a-453a) If the Government desired to cure the defect, it could have done so readily at that time. It did not.
The majority asserts that if the defendant had objected when the Government sought to introduce the testimony of White and Bilella that “would have warned the Government of the need to call Quintiliano or to prove his unavailability in other ways.” Op. at 849. As a matter of trial management, it would, of course, have been desirable for the defense to have specifically objected at the time on the sixth amendment ground, but not because the Government had to be warned of the need to call Quintiliano or prove his unavailability. The Government should have known that under Ohio v. Roberts, “in the usual case ... the prosecution must either produce, or demonstrate unavailability of, the declarant whose statement it wishes to use against the defendant.” See supra at 853. Calling Quintiliano or proving his unavailability was, as the majority recognizes, “a relatively simple matter for the Government.” Op. at 848. Taking such action when the motion to strike was tendered may have been an inconvenience for the Government, but an inconvenience so trivial should not be used to nullify an important constitutional safeguard.
Finally, the majority assumes that the district court overruled the defendant’s sixth amendment objection on the ground that it was untimely. It therefore declares that “the trial judge’s determination of timeliness” can only be reversed for an abuse of discretion. Op. at 850. The record, however, does not support this assumption. The trial judge heard and con*856sidered the defendant’s sixth .amendment motion to strike before the defense opened its case; he did not reject the motion as “untimely.” In fact, he made no ruling at all with respect to this constitutional issue. After hearing arguments of defense counsel and the prosecution when the Government rested, the trial judge either ignored the sixth amendment motion or impliedly equated it with the coconspirator exception. He only ruled: “We find that the Government has established the existence of an alleged conspiracy and the connection of each defendant with it by a clear preponderance of the evidence independent of the hearsay declarations.” (480a) This was the substance of the district court’s ruling on the defense arguments with respect to the coconspirator statements and the sixth amendment motion to strike the testimony. Thus, as this record stands, the court did not reject the sixth amendment motion on the ground of untimeliness. The prosecution raised no objection to the motion on the ground of untimeliness. The untimeliness question was raised for the first time by Judge Garth sua sponte in his dissent from the panel opinion. (Panel slip op. at 30.)
In any event, the confrontation issue is significant to the fact-finding process and to the ultimate determination of guilt or innocence. If the objection was not timely raised, this court may nonetheless take notice of the issue under the plain error rule.9 The denial of the right to cross-examine the declarant of the hearsay statements, especially under the circumstances we have here, violated a fundamental right of the accused and constituted serious prejudicial error. United States v. McKinney, 707 F.2d 381 (9th Cir.1983); United States v. Provencio, 554 F.2d 361 (9th Cir.1977); People v. Marine, 48 Ill.App.3d 271, 6 Ill.Dec. 25, 362 N.E.2d 454 (1977). “In exceptional circumstances, especially in criminal cases, appellate courts, in the public interest, may, of their own motion, notice error 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.” Silber v. United States, 370 U.S. 717, 718, 82 S.Ct. 1287, 1288, 8 L.Ed.2d 798 (1962) (per curiam) (quoting United States v. Atkinson, 297 U.S. 157, 160, 56 S.Ct. 391, 392, 80 L.Ed. 555 (1936)).
Courts have found no difficulty in reviewing a sixth amendment issue under the plain error rule for the waiver of fundamental constitutional rights “is not lightly to be found.” United States v. Provencio, 554 F.2d at 363. In United States v. McKinney, 707 F.2d 381 (9th Cir.1983), the defendant, as in this case, was convicted on Government testimony that constituted double hearsay. Although the sixth amendment issue was neither raised in the district court nor briefed or argued on appeal, the circuit court sua sponte considered the issue under the plain error rule and reversed. In United States v. Provencio, the court held that the introduction of depositions without any proof that the deposed witnesses were unavailable was such an obvious violation of the accused’s rights to confrontation that “it is unnecessary for us to decide whether the error in admitting the evidence without objection was plain error.” 554 F.2d at 362. The court refused to infer a waiver of a fundamental right from the failure of the defense counsel to object at the time of trial. Id. at 363.10
*857In People v. Marine, 48 Ill.App.3d 271, 6 Ill.Dec. 25, 362 N.E.2d 454 (1977), the appellate court reviewed a confrontation issue although the defendant had objected at trial only on the ground of hearsay. In rejecting the state’s argument that the defendant had waived the confrontation issue by only objecting on the ground of inadmissible hearsay, the court stated: “Even if we were to find a waiver of this issue for purposes of appeal, we regard the right to confrontation to be of such significance as to involve the application of the plain error rule.” Id. at 276, 6 Ill.Dec. at 29, 362 N.E.2d at 458 (citations omitted).
IV.
In summary, I believe that the sixth amendment issue was timely raised, even if the objection came at the close of the Government’s case. Had it not been timely, this court should review the issue under the plain error rule both because fundamental rights are involved and because the Government’s case rests largely on untested, devastating hearsay. Because the defendant has been denied the right of confrontation and cross-examination, “an essential and fundamental requirement for the kind of fair trial which is this country’s constitutional goal,” Barber v. Page, 390 U.S. 719, 721, 88 S.Ct. 1318, 1320, 20 L.Ed.2d 255 (1967) (quoting Pointer v. Texas, 380 U.S. 400, 405, 85 S.Ct. 1065, 1068, 13 L.Ed.2d 923 (1965), the judgment of conviction should be reversed and the case remanded for a new trial.
. Judge Aldisert and Judge Gibbons believe that . there was insufficient evidence of conspiracy measured by the "fair preponderance of independent evidence” test of United States v. Trotter, 529 F.2d 806, 811-12 (3d Cir.1976). See also Edward J. Sweeney & Sons, Inc. v. Texaco, 637 F.2d 105, 115-17 (3d Cir.1980), cert. denied, 451 U.S. 911, 101 S.Ct. 1981, 68 L.Ed.2d 300 (1981).
Several other circuits have adopted a more stringent test than the preponderance of evidence rule for the admission of coconspirator statements. ' They require "substantial evidence,” independent of the statements, showing the defendant’s participation in the conspiracy. United States v. Bulman, 667 F.2d 1374, 1379 (11th Cir.), cert. denied, 456 U.S. 1010, 102 S.Ct. 2305, 73 L.Ed.2d 1307 (1982); United States v. Jackson, 627 F.2d 1198, 1219 (D.C.Cir.1980); United States v. Grassi, 616 F.2d 1295, 1300-01 *851(5th Cir.1980); United States v. Petersen, 611 F.2d 1313, 1330-31 (10th Cir.1979).
. All references hereinafter to Quintiliano are to Joseph Quintiliano.
. This constituted the -“double hearsay” referred to in this dissent — Gibbs to Quintiliano and Quintiliano to Bilella and White.
. I do not mean to suggest that there is anything improper in relying on a presumption to show the continuation of a person’s participation in a conspiracy, but imposing such a presumption upon slight independent evidence implicating the defendant in the conspiracy only highlights the utter absence of flesh and blood in the Government's case upon which to rest the hearsay statements of a non-testifying conspirator.
The crucial portion of the alleged coconspirator statements was made approximately six months after Gibbs’s April 7 meeting in Quaker-town. To accomplish the admission, the Government relied upon a presumption that once it established Gibbs's participation in the conspiracy, membership continued thereafter until October 1980 unless Gibbs proved, by affirmative acts inconsistent with the object of the conspiracy, that he had withdrawn. There is no evidence in this record that Gibbs withdrew from the conspiracy after April.
. It is true, of course, that Quintiliano’s statements were against his penal interest because *854they disclosed his own complicity in the conspiracy. But this fact is hardly conclusive of the statements’ reliability, particularly because the critical portions of Quintiliano’s statements — his references to Gibbs — were not against his penal interest. See Davenport, The Confrontation Clause and the Co-Conspirator Exception in Criminal Prosecutions: A Functional Analysis, 85 Harv.L.Rev. 1378, 1395 (1972).
. The instant case is distinguishable from United States v. Weber, 437 F.2d 327, 337-40 (3d Cir. 1970), cert. denied, 402 U.S. 932, 91 S.Ct. 1524, 28 L.Ed.2d 867 (1971). In Weber, this court upheld against a constitutional attack the use of a coconspirator's out-of-court statement against the accused. Three factors distinguish Weber from the instant case. First, the hearsay evidence in Weber presented the "traditional hallmarks of reliability, because they were uttered spontaneously and they were against [the declarant’s] penal interest.” Id. at 340. Here, there are significant doubts about the reliability of Quintiliano’s statements. Second, the coconspirator statements in Weber were not crucial to the case, as they are here. Third, there was an absolute necessity for admission in Weber because the declarant had died before trial.
. The majority asserts that the issue was never raised by Gibbs during trial. "Had Gibbs by a specific objection, timely made, alerted the Government and the district court to the fact that no proof of unavailability had been presented by the Government, that deficiency could have been cured.” Op. at 847.
. Defense counsel further stated in support of his sixth amendment objection: “The men who should have been on that witness stand and ... whom I should have been able to cross-examine [were] Joe Quintiliano [and his brother] Jerry Quintiliano, the declarant[s] of the hearsay statements], and I have been denied through this case the right to confront and cross-examine ... the ultimate accusers in this case ... Joseph and Jerry Quintiliano.” (453a)
. 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.” Plain error has been defined as "serious and manifest” or "seriously prejudicial error" or "grave errors which seriously affect substantial rights of the accused.” United States v. Morales, 477 F.2d 1309, 1315 n. 17 (5th Cir.1973). See United States v. Nobel, 696 F.2d 231, 237 (3d Cir.1982).
. Other federal courts that have on appeal reviewed a confrontation argument, although the issue was not specifically raised at trial, include: United States v. Escobar, 674 F.2d 469 (5th Cir. 1982) (admission of officer’s testimony constituted plain error affecting substantial rights that court will review even absent timely objection at trial); Naples v. United States, 344 F.2d 508 (D.C.Cir.1964) (reception of double hearsay reviewed as plain error although not raised below); United States v. Dunn, 299 F.2d 548 (6th Cir.1962) (receipt of inadmissible hearsay that *857was the only evidence sufficient to make prosecution’s case reviewed by appellate court on its own motion).
In this court, we have often applied the plain error rule, sometimes in cases that did not even involve fundamental rights of the accused. See, e.g., United States v. Logan, 717 F.2d 84 (3d Cir. 1983) (failure to preserve issue of trial court’s failure to instruct on character witness reviewable as plain error); Government of the Virgin Islands v. Joseph, 685 F.2d 857 (3d Cir. 1982) (submission to jury of defendant's confession and minister’s letter when not admitted of record reviewable as plain error); Government of the Virgin Islands v. Brown, 685 F.2d 834, 839 (3d Cir. 1982) (”[t]he omission of an essential element of an offense in the charge to the jury ordinarily constitutes plain error, even in the absence of objection’’); United States v. DiPasquale, 677 F.2d 355, 359 n. 10 (3d Cir.1982) (submission of case to jury despite failure to renew motion for judgment of acquittal at close of all the evidence reviewable under plain error rule); Beardshall v. Minuteman Press Int'l, Inc., 664 F.2d 23 (3d Cir.1981) (erroneous instruction on burden of proof in civil case reviewable under plain error rule despite counsel’s failure to object).