dissenting:
While I fully agree with the panel opinion insofar as it sanctions the admission of evidence regarding Teague’s alleged possession of a firearm not mentioned in the indictment and of his prior gun purchases from Martin, I do not share the majority’s view that the action of Assistant United States Attorney Stuart constituted no violation of Teague’s due process rights.
In particular, I disagree with the majority’s conclusion that Teague suffered no harm from the approach initiated by the prosecutor to Martin’s attorney in a purported effort to guard against perjury.1 While the majority would confine its analysis in this situation to a finding that Stuart’s conduct was “dangerous and foolish,” I would hold that her actions constituted a due process violation harmful to Teague in their interference with his presentation of witnesses in his defense.
I would thus emphasize the teaching of the Supreme Court in Webb v. Texas, 409 U.S. 95, 93 S.Ct. 351, 34 L.Ed.2d 330 (1972) (per curiam), in which the Court reversed appellant’s conviction and granted a new trial upon a finding that the trial judge “effectively drove [the sole defense] witness off the stand” by his extended admonitions issued sua sponte during a jury recess.2 The witness’ refusal even to take *385the stand was deemed by a majority of the Court to constitute a due process violation, insofar as appellant was denied the right to present witnesses to establish his own defense. Quoting from Washington v. Texas, 388 U.S. 14, 19, 87 S.Ct. 1920, 1923, 18 L.Ed.2d 1019 (1967), the Court reiterated that the right to present witnesses “is a fundamental element of due process of law.” 409 U.S. at 98, 93 S.Ct. at 353.
This Court has likewise recognized the fundamental nature of the right, and has granted a new trial when governmental overbearing undermined the unfettered choice of a defense witness to testify freely. In United States v. MacCloskey, 682 F.2d 468 (4th Cir.1982), the United States Attorney prosecuting the ease made, on the second day of trial, a call to counsel for a key defense witness, who herself had originally been indicted with the defendant. Specifically, the United States Attorney suggested that the witness would be well advised to invoke her fifth amendment privilege should she choose to take the stand, and that she could be reindicted if she incriminated herself.3
As a result, in MacCloskey, when the witness took the stand, she claimed the fifth amendment privilege some thirty times. She thereby refused to answer certain questions before the jury that she had answered fully and in a completely exculpatory fashion for the defendant during her prior voir dire. Finding reversible error and granting a new trial, the Court observed:
[She] was the primary defense witness. The testimony she gave in the first voir dire was detailed and contradicted, or offered innocent explanations to, [other] damaging testimony. In short, her detailed testimony was vital to [the] defense. Since the evidence against [the defendant] was not overwhelming ... we are unable to say that the error was harmless.
Id. at 479 (emphasis original).
Teague’s case is quite similar to that of the defendant in MacCloskey, presenting an instance of gratuitous prosecutorial admonitions that were devoid of factual justification of any kind. Moreover, the evidence against Teague, like that against the defendant in MacCloskey, was, to my mind, “not overwhelming.” Thus, Stuart’s error cannot be deemed harmless. It is true that Martin’s counsel believed that Stuart’s real concern was that Martin should be admonished to testify in a truthful manner, and that at no time did Stuart try to influence counsel to have Martin testify in a particular way. Nonetheless, her communications first to counsel, then to Martin himself on the day he testified, left no doubt that “she expected completely truthful testimony ... and that a failure to testify truthfully ... would result in a review of [Martin’s] deferred prosecution agreement.” Stuart herself admitted she told counsel that “the pretrial diversion agreement would be revoked if [Martin] perjured himself.” Stuart’s own version of “the truth” should not predominate. The issue of truth vel non was for the jury, not for the prosecutrix. When questioned by the Court, the witness Martin admitted that, although no one from the United States Attorney’s Office had ever threatened him directly, he did feel that there was a “good chance they probably would try to charge [him] with perjury and nullify [his] pretrial release” if he deviated from the truth (as perceived by Stuart).
To be sure, Martin did take the stand and testify in a fully exculpatory manner for *386Teague, never pleading the fifth amendment. Nonetheless, although the transcript of his testimony reads in a seemingly forthright manner for one reviewing the printed text, the problem remains that an after-the-fact review by this Court cannot adequately discern the import of the critical nuances and subliminal effects of the way in which Martin delivered his testimony before the jury. Martin told the trial judge that he knew “the bind [he was] in testifying up here,” and that he did not like “being up here; ” at oral argument, Teag-ue’s counsel represented that Martin’s delivery and demeanor were those of one who was “nervous and scared.” Particularly since Stuart herself conducted the cross-examination, the pressure upon Martin could not dissipate, but rather was constantly before his eyes in the form of an ever-watchful, potentially menacing United States Attorney.
Given this factual scenario, it would be difficult for a reviewing court to determine whether Martin’s testimony and the jury’s reaction to it were actually affected by Stuart’s actions: a search for indications of. possible changes in his testimony would require a skill in divination that a court of review simply does not possess. As a general proposition, because any witness is subject to subtle motivations and instantaneous decision-making while on the stand (influencing every aspect of testimony from word choice, to tone and conviction of voice), a clear-cut determination of whether prosecutorial misconduct did or did not have a harmful effect on the testimony of a defense witness may often elude the Court. Compare United States v. Morrison, 535 F.2d 223, 228 (3rd Cir.1976) (Court acknowledges that “where the Government has prevented the defendant’s witness from testifying freely before the jury, it cannot be held that the jury, would not have believed the testimony or that the error is harmless”).
In the instant case, it appears that we cannot say that “absent [Stuart’s contacts it is] clear beyond a reasonable doubt that the jury would have returned a verdict of guilty.” United States v. Hasting, 461 U.S. 499, 103 S.Ct. 1974, 1981, 76 L.Ed.2d 96 (1983). In Hasting, the Supreme Court did reverse the Court of Appeals’ order for a new trial based on the improper closing argument of the prosecutor, since the error was determined to be harmless beyond a reasonable doubt. Finding that “a more compelling case of guilt is difficult to imagine” given the overwhelming weight of eyewitness testimony adduced against the defendants, the Court in Hasting reemphasized the teaching of Chapman v. California, 386 U.S. 18, 87 S.Ct. 824, 17 L.Ed.2d 705 (1967), that “it is the duty of a reviewing court to consider the trial record as a whole and to ignore errors that are harmless, including most constitutional viola-tions____” — U.S. at-, 103 S.Ct. at 1980 (citations omitted).
Teague’s situation may be readily distinguished from that of the defendants in Hasting, however. The evidence against Teague was not truly “compelling,” and Martin’s testimony was directed specifically to the issues of Phillips’ purchase and continued possession of the gun, and to the fact that Martin never saw the gun in Teague’s possession. The majority asserts that because Martin was not present on January 31, 1979 when Teague was arrested in his car with the gun, Martin “could give no helpful testimony about Teague’s possession of the weapon” that day. However, Teague vigorously contested that he had any knowledge that the gun was in his car, and testified that Phillips had borrowed the car and left the gun under the front seat. Thus, Martin’s testimony was critical on the issue of Teague’s knowing possession of the gun on January 31, 1979.4
*387It is possible that a single, factual mention of the consequences of perjury, perhaps in response to direct questioning by the witness, may not constitute misconduct or harmful error in some circumstances.5 By contrast, an openly aggressive stance on the part of the prosecuting attorney would rise to the level of harmful error.6 It seems clear that Stuart’s behavior falls between these two points on the spectrum of prosecutorial misconduct; in my opinion, her actions do not fall within that band of error which is harmless beyond a reasonable doubt.
Of course, it is well to remember the observations of the Supreme Court in Hasting that “reversals of convictions under, the court’s supervisory power must be approached ‘with some caution,’ ” 461 U.S. at -, 103 S.Ct. at 1979 (citations omitted), but where the error is harmful (i.e., when the conviction might not have been obtained absent the error), the potent relief afforded by the exercise of this Court’s supervisory powers is wholly in order. I would thus emphasize the Court’s duty “to implement a remedy for violation of recognized rights ...; to preserve judicial integrity by ensuring that a conviction rests on appropriate considerations validly before the jury ...; and finally, ... to deter illegal conduct.” United States v. Hasting, 461 U.S. at —, 103 S.Ct. at 1978-79.
The concerns articulated by the Court of Appeals for the Fifth Circuit in a similar case of prosecutorial misconduct are well taken and applicable to the ease at bar. In United States v. Hammond, 598 F.2d 1008 (5th Cir.1979), an FBI agent’s threats of “nothing but trouble” for two important defense witnesses caused those witnesses to refuse to testify. The trial judge read to the jury a stipulation as to what the witnesses would have said, and instructed the jury to give the stipulated testimony the same weight as it would have given live testimony. Relying in part on Webb v. Texas, supra, the Court of Appeals refused to permit the harmless error rule “to be a cover-up for every prosecutorial error,” and held that such a due process violation was harmful per se. 598 F.2d at 1014. Like the defendant in Hammond, Teague presents a case in which witness credibility was directly at issue: Martin was a primary defense witness, his testimony bearing directly on Teague’s alleged possession of the gun on the day of purchase and thereafter.
Moreover, as the Fifth Circuit observed in Hammond, it is difficult to imagine “that such a violation of due process would result from anything but intentional conduct on the part of the government____” Id. at 1013. If any warning regarding the consequences of perjury appears necessary, that warning should come from the trial judge himself, not from an overly zealous prosecuting attorney eager to assume responsibility for assuring an attitude she regards as proper on the part of testifying witnesses. Already standing as potent symbols of the Government’s power in a criminal proceeding, prosecuting attorneys should not be permitted to capitalize upon that power to gain increased influence by subtle, or not so subtle, psychological manipulation of witnesses.7
. It should be emphasized that Stuart’s approach to counsel for Martin was simply an exhortation. It was not based on the availability of factual information in the Government's hands, unknown to the witness, which might support a charge of perjury if contradictory evidence were forthcoming.
. The trial judge told the witness, “[Ajnythmg you say can and will be used against you____ You don’t owe anybody anything to testify and *385it must be done ... with the thorough understanding that you know the hazard you are taking." 409 U.S. at 95-96, 93 S.Ct. at 352. He also reminded the witness, who had a prior criminal record and was then serving a sentence, that he could be charged with perjury and could jeopardize his future parole opportunities if he were less than truthful on the stand.
. While it is true that the original indictment against the witness had been dropped before the defendant’s trial began, the witness testified at voir dire before the trial judge that "she was afraid that her indictment would not be dismissed.” 682 F.2d at 476. Thus,' her fear of prosecution remained an active one, regardless of any misunderstanding on her part of the procedural disposition of her case.
. It is true that a violation of 18 U.S.C.App. § 1202 need not be predicated on specific intent. See United States v. Harvill, 501 F.2d 295 (9th Cir.1974) (defendant need not have acted knowingly, purposely intending to violate the law). Nevertheless, it is also clear that to support a conviction under the section, it must be shown that the defendant knew he was in possession of a firearm. See United States v. Oliver, 683 F.2d 224 (7th Cir.1982); and United States v. Laymon, 621 F.2d 1051 (10th Cir.1980).
. See United States v. Valdes, 545 F.2d 957, 960 (5th Cir.1977) (defendant fails to establish governmental impropriety when District Attorney spoke to defense witness "only once" during a lengthy pretrial interview to inform him of possible consequences of perjury, and witness’ "own counsel was present throughout those proceedings").
. See Morrison, 535 F.2d at 227 (applying error per se rule in a clear case of prosecutorial misconduct when the United States Attorney contacted the defense witness on at least three occasions regarding possible prosecution, subpoenaed the witness to compel a “highly intimidating personal interview at the prosecutor's office” immediately before she was called to the stand to testify, and threatened both perjury charges and prosecution as a juvenile if the witness incriminated herself on the stand).
. See also United States v. Thomas, 488 F.2d 334 (6th Cir.1973) (per curiam) (adopting a rule of error per se, Court refused to consider balancing the apparently overwhelming evidence of guilt against the allegedly insufficient prejudice to defendant to find harmless error; Washington v. Texas clearly established the fundamentality of a defendant’s right to produce witnesses on his behalf, regardless of the weight of the evi*388dence against him). But see United States v. Simmons, 670 F.2d 365, 372 n. 4, 78 L.Ed.2d 119 (D.C.Cir.1982) (per curiam), cert. denied, — U.S.-, 104 S.Ct. 121 (1983) (defendant must prove "substantial prejudice” to obtain reversal of conviction on grounds that prosecutor deprived him of defense testimony by threatening a witness).