WINTER, Circuit Judge:
Defendants, James L. Sarvis and Irie E. Leonard, were tried jointly with Francis A. Salters on a five-count indictment charging them with felony murder,1 first degree murder,2 armed robbery,3 robbery,4 and second degrée burglary.5 The jury found Sarvis guilty of armed robbery and second degree burglary. It convicted Leonard of first degree murder, armed robbery, and second degree burglary. Salters was acquitted.
Sarvis and Leonard both appeal. They advance a number of contentions as to why their convictions should be reversed. We conclude that there were three errors of sufficient magnitude to warrant reversal and a new trial. They were: (1) the failure of the district [958]*958court to instruct the jury, as requested by defendants, to scrutinize carefully the testimony of two important government witnesses to whom immunity had been granted; (2) the district court’s limitation of the cross-examination of one of the important government witnesses with reference to two unrelated felony charges pending against him; and (3) the district court’s failure to give an immediate cautioning instruction when the testimony of an arresting officer was admitted to impeach Leonard’s testimony in his own defense. Although we do not find them to be grounds for reversal, we are constrained to discuss some of the other issues raised by defendants’ remaining contentions because of the likelihood that they will arise again on retrial.
I.
FACTS.
While we will state additional facts in the discussion of the contentions to which they are especially pertinent, we begin with a general outline of the case. Benjamin Rudd was brutually robbed and murdered in his basement apartment at 854 21st St., N.E., Washington, D.C. during the evening of September 15-16, 1970. Rudd arrived home in a taxicab about 11:00 p. m. When he left the cab, a group of young men standing across the street called to him. Rudd joined the group for a minute and then crossed the street to his apartment, accompanied by two of them. Six witnesses identified one of the men accompanying Rudd as the defendant Leonard. Three witnesses identified the other as the defendant Sarvis. Rudd apparently felt threatened and sought refuge in the apartment of his neighbor, Virginia Gaskins. Eventually, Rudd was coaxed out into the apartment hallway.
At this point, the two men identified as Sarvis and Leonard assaulted Rudd; Leonard knocked him down, took his keys and wallet, and dragged him into the apartment. Then, about six members of the group began to plunder Rudd’s apartment. Among these were Albert Jones and Curtis Hughes, both of whom testified for the government under a grant of immunity, and Francis Salters, the third defendant. Other members of the group, including Larry Mauldin and Robert King, watched from outside the apartment building but did not enter. Both Mauldin and King testified for the government, as did Donald Montgomery, another member of the group who had departed earlier.
While these men rifled Rudd’s apartment, Rudd was beaten, tortured, and eventually killed. Although none of the witnesses observed the lethal blow, their testimony pointed to the culpability of Leonard or Sarvis, or both. Jones testified that Leonard told him “he [Leonard] was going to kill Ben .... There was nothing else to do . because he had seen . . . his [Leonard’s] face and Jimmie’s [Sarvis’] face.” Hughes testified that he observed Sarvis and Leonard torturing the deceased. Hughes further testified that Leonard told him he was going to kill Rudd, and that he observed Leonard take a butcher knife from the kitchen to the bedroom where Sarvis was harassing the victim with a sculpture knife. Hughes also testified that as Salters left the apartment, Salters said that “they were going to kill him.”
Sarvis and Leonard based their defense on separate alibis. Leonard testified; Sarvis did not. Salters in effect admitted his presence, but contended that he did not participate in the crimes. He did not testify.
II.
ACCOMPLICE AND IMMUNITY INSTRUCTIONS
In addition to the highly incriminating testimony of Jones and Hughes, both of whom were obviously accomplices, a substantial portion of the government’s evidence came from witnesses who were involved, either as onlookers or participants, with the group of young men whose members allegedly killed the vie[959]*959tim and ransacked his apartment.6 During the police investigation, Jones and Hughes first denied knowledge of the crime, but later admitted their complicity and agreed to cooperate. The government granted both immunity pursuant to 18 U.S.C. § 6002 (Supp.1973).7 Thus, Jones and Hughes testified both as accomplices and under a grant of immunity.
Neither Sarvis nor Leonard specifically requested the district court to instruct the jury that the testimony of Jones and Hughes should be received with caution because they were accomplices; rather, they requested instructions admonishing the jury to receive this evidence with caution because Jones and Hughes had been granted immunity.8 The district court denied the requested immunity instruction. While it offered to instruct that the testimony of Jones and Hughes, who testified under a grant of immunity, “is to be scrutinized and evaluated in the same manner as the testimony of all other witnesses who testified during the case,” in fact, the district court gave only the standard instruction as to witnesses’ testimony and failed to mention the immune status of Jones and Hughes. Sar-vis and Leonard claim error in the failure to give either an accomplice or an immunity instruction.
A. There can be no doubt but that an accomplice instruction would have been proper, because, in Crawford v. United States, 212 U.S. 183, 203-204, 29 S.Ct. 260, 268, 53 L.Ed. 465 (1909), the Supreme Court held that the testimony [960]*960of a witness who turned “state’s evidence”
is not to be taken as that of an ordinary witness of good character in a case, whose testimony is generally and prima facie supposed to be correct. On the contrary, the evidence of such a witness ought to be received with suspicion, and with the greatest care and caution, and ought not to be passed upon by the jury under the same rules governing other and apparently credible witnesses.
The Court has characterized accomplice testimony as “inevitably suspect” and unreliable. Bruton v. United States, 391 U.S. 123, 136, 88 S.Ct. 1620, 20 L.Ed.2d 476 (1968). See On Lee v. United States, 343 U.S. 747, 757, 72 S.Ct. 967, 96 L.Ed. 1270 (1952).
We have no doubt that it is better practice for a district court sua sponte to caution the jury concerning an accomplice’s testimony, and that it is reversible error to refuse to give a requested accomplice instruction. Freed v. United States, 49 U.S.App.D.C. 392, 266 F. 1012 (1920). However, neither defendant requested an accomplice instruction; nor did either object to its omission. Rule 30, F.R.Cr.P., bars the claim on appeal unless the district court’s failure to give an accomplice instruction was “plain error” in the circumstances of this case. Rule 52(b), F.R.Cr.P.
That the failure to give an accomplice instruction may, in certain exceptional circumstances, constitute plain error has been recognized among the circuits. Tillery v. United States, 411 F.2d 644 (5 Cir. 1969); McMillen v. United States, 386 F.2d 29, 35-36 (1 Cir. 1967), cert, denied, 390 U.S. 1031, 88 S.Ct. 1424, 20 L.Ed.2d 288 (1968).9 But such recognition has not been extended to a case like the instant one where nonaccomplice testimony corroborated the accomplice testimony and was sufficient in itself to serve as a basis for conviction. Thus in Tillery, where the court found plain error, virtually all of the government’s case rested upon the accomplice’s testimony, the accomplice changed his testimony several times prior to trial to the extent that the court characterized it as “extremely unreliable, if not incredible and insubstantial” (Id., 411 F.2d at 648), and the case was factually close.10 Similarly, in McMillen, plain error was noticed where the district court instructed as to the now discredited presumption of truthfulness, “[t]he only evidence connecting . . . [defendant] with the . . . [crime] came from the mouths of others involved in that escapade,” and “[t]hese were not accomplices who had paid their price to society and were free from carrot or stick.” 386 F.2d at 36. See also United States v. Evans, 398 F.2d 159, 163-164 (3 Cir. 1968).
By contrast, in the instant ease, non-accomplice testimony corroborated the accomplice testimony to a significant extent against Leonard, and to a lesser extent against Sarvis. As to Leonard, four other witnesses substantially corroborated the testimony of Jones and Hughes. While three of these witnesses were at least onlookers, they did not participate in the robbery or murder and were not accomplices. Gaskins, the fourth witness, was the victim’s neighbor and was in no way connected with the miscreant group. One other witness, King, identified Sarvis. Although King did “hang around” with the group to watch from the-, outside of the apartment building, King did not participate [961]*961in looting Rudd’s apartment, so that he, too, was not an accomplice.
Of course, Jones and Hughes were under carrot and stick to some extent and they changed their stories before trial, thereby casting some doubt on their credibility. They did so once from claiming innocence to admitting guilt; but, unlike the accomplice in Tillery who changed his story four times, their behavior was not extraordinary and does not evince the same disposition to prevarication which prompted the court in Tillery to discount heavily the accomplice’s testimony. Moreover, the jury was not instructed that they were presumed truthful. Both with regard to Leonard and Sarvis, we conclude that the omission of the accomplice instruction was not plainly erroneous.
B. Defendants’ contention that there .was error in the refusal to grant a special instruction with regard to the testimony of witnesses to whom the government has granted immunity, stands on a surer footing because the requests were made and refused. Defendants have not cited, nor have we found, any ease which holds that it is reversible error to refuse the requested immunity instruction. However, we find persuasively analogous the rule requiring the district court, upon request, to caution the jury that the testimony of paid informers should be received with circumspection. Fletcher v. United States, 81 U.S.App.D.C. 306, 158 F.2d 321 (1946); United States v. Masino, 275 F.2d 129, 133 (2 Cir. 1960). See United States v. Kinnard, 150 U.S.App.D.C. 386, 465 F.2d 566 (1972).
In On Lee, 343 U.S. at 757, 72 S.Ct. at 973, the Court articulated the rationale of the rule that a trial court upon request should instruct caution with regard to the testimony of paid informers:
The use of informers, accessories, accomplices, false friends, or any of the other betrayals which are “dirty business” may raise serious questions of credibility. To the extent that they do, a defendant is entitled to broad latitude to probe credibility by cross-examination and to have the issues submitted to the jury with careful instructions.
Like the paid informer who has a pecuniary interest in testifying, or an accomplice who has a penal interest in shifting guilt to his cohort, a witness who has been granted immunity has an interest in incriminating another to save himself. Cf. McMillen, supra. Typically, as in this case, the government offers immunity to a lesser or minor co-conspirator, or accomplice, who stands in jeopardy of being convicted, as an incentive to testify against others more significantly involved. A potential witness, so confronted, realizes that he can procure his own freedom by incriminating another, and therein lies his motivation to falsify.11 We hold, therefore, that the district court committed reversible error in refusing to instruct the jury when requested, to consider with caution the testimony of Jones and Hughes, important government witnesses who had been granted immunity from prosecution. We add only that we are not to be understood as saying that, on retrial, if Sarvis and Leonard request an instruction with regard to Jones and Hughes that their testimony is to be viewed with caution both because they were accomplices and because they have been grant[962]*962ed immunity from prosecution, they will be entitled to double instructions. Rather, the district court should merge both requests into a single instruction that the testimony of Jones and Hughes is to be scrutinized with caution because they are accomplices and because they have been granted immunity.
III.
IMPEACHMENT — PENDING FELONY CHARGES.
We find reversible error also in the district court’s limitation of the efforts of Sarvis and Leonard to cross-examine Jones concerning two unrelated felony charges which were pending against him.12 Prior to Jones’ voir dire testimony, Mr. Nesbitt, the Assistant United States Attorney prosecuting the case, advised the court and defense counsel that a narcotics charge and a robbery charge were currently pending against Jones in the district. Mr. Nesbitt then represented, no doubt in absolute good faith, that:
I have not been in touch with either counsel at any stage of the proceeding [against Jones], your Honor, and have made no representation myself, with regard to disposition of these cases, and to my knowledge, Mr. Kleiboemer [the Assistant United States Attorney prosecuting the other charges] never made any representations regarding dispositions either to the Defendant or to counsel.
In fact, the previous day, another Assistant United States Attorney had advised Jones’ counsel that the government would be willing to accept a plea of guilty to one misdemeanor in either case and would ask the court to dismiss the other charges. Jones’ counsel immediately advised Jones of the government’s offer while Jones was in the witness room waiting to testify for the government in this case.13 Jones testified for the government on voir dire the next day and at trial later in the week. He had previously testified for the government before the grand jury.
At trial, defense counsel attempted to cross-examine Jones by asking whether the government had made any disposition of the unrelated charges pending against him. The district court sustained the government’s objection, ruling that the defense had no factual basis for this line of questions. It further instructed the jury to disregard defense counsel’s questions because the defense had no proof that any disposition had been made. The district court’s ruling effectively foreclosed the defense from unearthing and establishing any factual basis for bias or self-interest arising out of the pending charges. Undoubtedly, the district court’s ruling was based on the government’s innocent misrepresentation.
It has generally been held that a witness’ self-interest or bias “may be shown [963]*963in a criminal case when the witness testifies for the state and it is shown that an indictment is pending against him, or that he is an accomplice or co-indictee in the crime on trial.” McCormick, Evidence § 40 (Cleary ed. 1972) (footnotes omitted). In Masino, the court reversed where the district court had barred defense cross-examination of two prosecution witnesses concerning the recent dismissal of narcotics charges against them. The court’s reasoning warrants quotation, at some length:
When a witness in a criminal case is being questioned as to his possible motives for testifying falsely wide latitude should be allowed in cross-examination. ... It was highly relevant and material to bring out that the . . . [state criminal] charge . . . had been quashed upon the intercession of the Assistant United States Attorney. This is the kind of situation where the widest possible cross-examination should be permitted. The appellant was entitled to have the jury know what had happened with respect to the charge, including any part which representatives of the government had played, so that the jury could draw its own conclusions with respect to possible motives for [the witness’] testimony.
******
[T]he indictment and its disposition was a matter so intimately related to [the witness’] possible motives to falsify and his relationship to the government which had called him as its witness that the trial court should have allowed full exploration of these matters on cross-examination.
275 F.2d at 132-133.14
The permissible scope of exploration on cross-examination is not curtailed by the absence of explicit government promises of leniency, for the defense may attempt to show government “conduct which might have led a witness to believe that his prospects for lenient treatment by the government depended on the degree of his cooperation.” United States v. Campbell, 426 F.2d 547, 549 (2 Cir. 1970). Jones might reasonably have surmised that there was some connection between his testimony in this cas'e and the government’s offer, arriving as it did while he was waiting to testify in this case.15
The defendants were entitled to be given broad latitude in their effort to impeach the credibility of government witnesses on cross-examination. Alford v. United States, 282 U.S. 687, 51 S.Ct. 218, 75 L.Ed. 624 (1931). The district court’s ruling and instruction severely circumscribed defense counsel in this regard and therefore was reversible error. Since we reach this conclusion, we need not independently consider the prejudicial effect of the government’s erroneous but good faith representations to the court and defense counsel. Compare Giglio v. United States, 405 U.S. 150, 92 S.Ct. 763, 31 L.Ed.2d 104 (1972) with United States v. Hykel, 461 F.2d 721 (3 Cir. 1972); United States ex rel. Dale v. Williams, 459 F.2d 763, 767 (3 Cir. 1972). See also Brady v. Maryland, 373 U.S. 83, 83 S.Ct. 1194, 10 L.Ed.2d 215 (1963); Napue v. Illinois, 360 U.S. 264, 79 S.Ct. 1173, 3 L.Ed.2d 1217 (1959).
[964]*964IV.
IMPEACHMENT — IMMEDIATE LIMITING INSTRUCTION.
The final error requiring reversal and a new trial arose during Leonard’s testimony in his own behalf. On cross-examination, the prosecutor asked Leonard whether he had told the arresting officer that the “other man” — Sarvis — lived across the street. Leonard unequivocally denied making the statement.16 On rebuttal, the government called the arresting officer who was permitted to testify, over Sarvis’ objection, that Leonard had made the alleged statements to him. Again over Sarvis’ objection, the prosecutor then engaged the arresting officer in a long colloquy detailing the events of Sarvis’ arrest.
Sarvis contends that the district court erred in admitting the officer’s testimony about Leonard’s alleged statement, and that even if the testimony was admissible the district court erred in failing immediately to instruct the jury that it was admissible solely for the purpose of impeaching Leonard’s credibility. Sarvis further contends that the remainder of the officer’s testimony was improper and irrelevant.17
Defendants’ first contention is substantially foreclosed by Nelson v. O’Neil, 402 U.S. 622, 629-630, 91 S.Ct. 1723, 1727, 29 L.Ed.2d 222 (1971), which held that
where a co-defendant takes the stand in his own defense, denies making an alleged out-of-court statement implicating the defendant, and proceeds to testify favorably to the defendant concerning the underlying facts, the defendant has been denied no rights protected by the Sixth and Fourteenth Amendments.
Since Sarvis could have cross-examined Leonard, the admission of Leonard’s and the officer’s testimony concerning Leonard’s alleged extra-judicial statement does not transgress the confrontation clause. O’Neil, supra. United States v. Hawk Wing, 459 F.2d 428 (8 Cir. 1972). Cf. Bruton, supra.
The officer’s rebuttal testimony contradicting Leonard’s denial was admissible, however, solely as impeachment evidence. The jury could not consider it as substantive evidence against Leonard, or in any respect whatsoever against Sar-vis. Sarvis did not request a limiting instruction immediately after the officer’s testimony and the district court did not give one. In its charge, the district court did instruct the jury in general terms as to the limited effect to be given impeachment evidence. After the district court’s charge, Sarvis requested an additional instruction advising the jury to apply “[a] voluntary confession or admission” only against the defendant making it, but did not otherwise object. The district court denied the request.
In this circuit, it has been firmly established that when evidence is admitted for the limited purpose of impeaching a witness, it is plain error, in the absence [965]*965of manifest waiver, for the district court to omit an immediate cautioning instruction. Jones v. United States, 128 U.S.App.D.C. 36, 385 F.2d 296, 300 (1967) (Per Curiam); United States v. Thompson, 150 U.S.App.D.C. 403, 465 F.2d 583, 585 n. 10 (1972). See United States v. McClain, 142 U.S.App.D.C. 213, 440 F.2d 241, 245-246 (1971). See also United States v. Bobbitt, 146 U.S. App.D.C. 224, 450 F.2d 685, 691 (1971). There is no indication in the record that Sarvis or Leonard purposefully waived the instruction. The district court’s general instruction on impeachment evidence, buried as it was in a very long charge and coming at the end of a three-week trial, did not adequately protect the interests which gave rise to this rule. The purpose served by a limiting instruction is particularly salutary in a joint trial where, as here, the jury may not consider the evidence, even as restricted, as against one defendant. In Nelson, the court noted that the trial judge had cautioned the jury not to consider as against one defendant the evidence of his co-defendant’s prior extrajudicial statement. 402 U.S. at 624, 91 S.Ct. 1723, 29 L.Ed.2d 222. Hawk Wing was careful to note that after the government’s rebuttal witness testified to one defendant’s prior inconsistent statement, the trial judge cautioned the jury concerning the impeachment character of the testimony. 459 F.2d at 430.
We therefore conclude that admission of the testimony concerning Leonard’s alleged prior inconsistent statement without an immediate instruction limiting its admissibility to impeachment purposes requires reversal of both Sar-vis’ and Leonard’s convictions.
V.
SEVERANCE.
We' reject the claim of reversible error in the district court’s refusal to grant defendants’ repeated motion for severance. Each defendant advances multiple arguments to bolster this contention. After setting out some general considerations, we will discuss them seriatim in the factual context in which each arose.
A. Rule 8(b) of the F.R.Cr. P. authorizes joinder where “two . . . defendants . . . are alleged to have participated in the same act or transaction . . . constituting an offense . . ..” Joinder of the three defendants was therefore proper. Rule 14 provides the district court with discretion to grant a severance “[i]f it appears that a defendant ... is prejudiced by a joinder . . . .” Pursuant to the mandate of Rule 14, “the trial judge has a continuing duty at all stages of the trial to grant a severance if prejudice does appear.” Schaf-fer v. United States, 362 U.S. 511, 516, 80 S.Ct. 945, 948, 4 L.Ed.2d 921 (1960); United States v. Wilson, 140 U.S.App. D.C. 220, 434 F.2d 494, 499 (1970). Since the district court possessed “great discretion” with respect to the grant or denial of a severance, its decision will be reversed only upon an affirmative showing that the district court clearly abused this discretion and that a defendant was prejudiced thereby. United States v. Gambrill, 146 U.S.App.D.C. 72, 449 F.2d 1148, 1159 (1971); Wilson, 434 F.2d at 500. In reviewing the exercise of the district court’s discretion, this court has approvingly concluded that “[t]he balance has been struck in favor of joint trials . . .,” United States v. Hines, 147 U.S.App.D.C. 249, 455 F.2d 1317, 1334, cert, denied, 406 U.S. 975, 92 S.Ct. 2427, 32 L.Ed.2d 675 (1972), quoting United States v. Krechevsky, 291 F. Supp. 290, 294 (D.C.1967). This reflects the strong federal policy favoring joinder because it
expedites the administration of justice, reduces the congestion of the trial dockets, conserves judicial time, lessens the burden upon citizens who must sacrifice both time and.money to serve upon juries, and avoids the necessity of recalling witnesses who would otherwise be called upon to testify only once.
Hines, 455 F.2d at 1334, quoting Parker v. United States, 404 F.2d 1193, 1196 (9 [966]*966Cir.1968), cert, denied, 394 U.S. 1004, 89 S.Ct. 1602, 22 L.Ed.2d 782 (1969). See Rakes v. United States, 169 F.2d 739, 744 (4 Cir.), cert, denied, 335 U.S. 826, 69 S.Ct. 51, 93 L.Ed. 380 (1948).
B. Sarvis contends that he was prejudiced, and severance was required, because the government’s case against his co-defendants was more damaging that the case against him. Six witnesses testified that Leonard was one of the men who entered the victim’s apartment, while only three — Jones, Hughes, and King — similarly placed Sarvis. Although there was some confusion in the testimony of these and other witnesses concerning Sarvis’ clothes, all three witnesses firmly and unequivocally identified Sarvis at trial. Sarvis hypothesizes that due to this disparity in the weight of the evidence, the jurors may have permitted the evidence against his co-defendants to cloud their consideration of his guilt. This court has recognized that “a disparate quantum of evidence against each of two co-defendants may conceivably require a severance under some circumstances,” but only if the evidence against one is “ ‘far more damaging.’ ” Gambrill, 449 F.2d at 1159; McHale v. United States, 130 U.S.App.D.C. 163, 398 F.2d 757, cert, denied, 393 U.S. 985, 89 S.Ct. 462, 21 L.Ed.2d 447 (1968).
Although the evidence placing Leonard at the crime was both quantitatively and qualitatively greater than the evidence against Sarvis, the disparity does not meet the “far more damaging” test. The evidence against Sarvis was both substantial and compelling. It was in no sense an inconsequential part of the trial, swallowed and tainted by a relatively overwhelming mass of evidence against Leonard. Cf. United States v. Kelly, 349 F.2d 720, 777 (2 Cir.1965), cert, denied, 384 U.S. 947, 86 S.Ct. 1467, 16 L.Ed.2d 544 (1966). On this record, the jury could “reasonably be expected to compartmentalize the evidence as it relates to separate defendants.” United States v. DeLarosa, 450 F.2d 1057 (3 Cir.1971), cert, denied sub nom., Jones v. United States, 405 U.S. 957, 92 S.Ct. 1188, 31 L.Ed.2d 235 (1972). And the district court specifically instructed the jury to determine the guilt or innocence of each defendant by considering only his own conduct and the evidence which applied to him. Finally, the verdicts demonstrate that the jury understood and fulfilled its obligation under the charge.
C. Both Sarvis and Leonard contend that prejudice requiring severance resulted from the apparent conflict between their defenses on the one hand, and Salters’ on the other hand, and also between their defenses. Sarvis and Leonard relied on separate alibi defenses. Salters admitted his presence, but denied participation in the killing. Sal-ters did not testify, but prosecution witnesses Hughes and Mauldin were permitted to testify that Salters said at the scene of the crime that Sarvis and Leonard had knocked out the victim, were tearing his apartment apart, and were going to kill him. In his closing argument, counsel for Salters emphasized that Salters did not participate in the killing by often referring to the perpetrators as “they,” with the implication, according to Sarvis and Leonard, that the pronoun “they” pointed Salters’ accusing finger at them. Finally, Leonard urges that Sarvis’ efforts to discredit the testimony which placed him with Leonard had the effect of undermining Leonard’s alibi defense.
Defendants rely heavily on Rhone v. United States, 125 U.S.App.D.C. 47, 365 F.2d 980, 981 (1966), where this court recognized that:
Prejudice from joinder of defendants may arise . . . where the defendants present conflicting and irreconcilable defenses and there is a danger that the jury will unjustifiably infer that this conflict alone demonstrates that both are guilty. (Emphasis added).
See DeLuna v. United States, 308 F.2d 140 (5 Cir.1962). Subsequent cases stress the word “alone,” and conclude [967]*967that where independent evidence of each defendant’s guilt supports the jury’s verdict, the conflict does not necessarily prejudice the defendants to the extent that a district court’s refusal to sever must be considered a clear abuse of discretion. United States v. Hurt, 155 U.S.App.D.C. 217, 476 F.2d 1164 (1973); Wilson, 434 F.2d at 500; United States v. Robinson, 139 U.S.App.D.C. 286, 432 F.2d 1348 (1970). See Hines, 455 F.2d at 1333-1335. But cf. ABA Project on Minimum Standards for Criminal Justice, Joinder and Severance, § 2.3(b) at 41 (1967). The spectacle of conflicting stories and veiled accusations emanating from the defense table no doubt adversely affected defendants’ defenses. However, the alibis of Sarvis and Leonard were not contradicted solely by Salters’ defense. The government presented substantial independent evidence incriminating Sarvis and Leonard. Moreover, much of the government’s evidence came from other members of the group who, like Salters, were present during the commission of the crimes. Hughes, Jones, Mauldin and King all testified that they were present and observed some of the events. The testimony of these witnesses diminished the impact of Salters’ defense which derived significance mainly from the implication that he was present and observed Sarvis and Leonard. Mauldin and Hughes did testify to statements by Salters which incriminated Sarvis and Leonard. And for obvious reasons, counsel for Salters did not join the vigorous objection of Sarvis and Leonard to his hearsay testimony. But, as will be shown, this hearsay testimony would have been admissible even if Sarvis and Leonard had been tried separately. See Hurt, supra; Wilson, 434 F.2d at 502.
Neither Sarvis nor Leonard objected to the closing argument by counsel for Salters. He did not refer to the other defendants by name. With the evidence establishing that at least six men were in the group which ransacked the victim’s apartment we cannot say that Salters’ counsel’s unvariegated emphasis the word “they” in the closing argument constituted plainly prejudicial error. Rule 52(b), F.R.Cr.P. Thus, it cannot be said that the conflict between the defendants’ alibi defense and Sal-ters’ defense created a serious danger that the jury would seize upon it alone as the dispositive indicia of guilt. of
The danger that Salters’ conflicting defense might have seriously prejudiced Sarvis and Leonard was, however, exacerbated by Salters’ failure to testify and the consequent inability of Sarvis and Leonard to cross-examine him. In Hurt and Wilson, the court based its reasoning to some extent on the fact that the defendants whose defenses conflicted all testified and were subject to cross-examination.
In Gambrill, one defendant in a joint trial proffered two witnesses whose testimony provided alibis for both the defendant and his co-defendant. The co-defendant, wanting to disassociate himself from what he considered to be a patently incredible alibi, sought and obtained an instruction from the court which limited the alibi testimony to the defendant who proffered the witnesses. This instruction had the effect of implicitly impugning the proffering defendant’s alibi, an effect he could not dispel because the co-defendant’s failure to testify precluded cross-examination. Although the court reversed on another ground, it suggested that if a similar problem arose on remand, the district court should grant a severance. 449 F. 2d at 1161-1162.
Even though a district court might properly exercise its discretion in these circumstances to grant a severance, the refusal to do so here was not a clear abuse of discretion. The damaging implications of Salters’ defense were corroborated by substantial testimony from several similarly situated witnesses. The inability of Sarvis and Leonard to cross-examine Salters thus did not create such prejudice that the district court’s refusal to grant their motions for a severance constituted a clear abuse [968]*968of discretion. “[T]hat a defendant might have a better chance of acquittal if tried separately does not establish his right to severance.” Wilson, 434 F.2d at 501.18
D. Witnesses Hughes and Mauldin were permitted to testify over the objections of Sarvis and Leonard to statements made by Salters during the commission of the crimes which incriminated Sarvis and Leonard.19 The district court apparently admitted Maul-din’s testimony only for the purpose of proving that Salters made the statement and not to prove the truth of Salters’ statement, although its ruling is not without confusion and it gave no explicit instructions on this point. The district court apparently admitted Hughes’ testimony under the rather nebulous exception termed “res gestae.”
The exception to the hearsay rule for contemporaneous declarations which partake of the event is often subsumed under the rubric of res gestae, and is an increasingly recognized exception. McCormick, supra, § 298. See Model Code of Evidence Rule 512(a); Proposed Federal Rule of Evidence 803(2). Similarly, res gestae often is used to refer to another generally recognized exception to the hearsay rule for spontaneous declarations or excited utterances. Murphy Auto Parts Co. v. Ball, 101 U.S.App.D.C. 416, 249 F.2d 508 (1957), cert, denied, 355 U.S. 932, 78 S.Ct. 413, 2 L.Ed.2d 415 (1958). See McCormick, supra, § 297; 6 Wigmore, supra, §§ 1749-1757, 1768. The testimony of Mauldin and Hughes may properly have been admitted under either of these exceptions.
Sarvis and Leonard contend that since they could not cross-examine their co-defendant Salters, admission of hearsay testimony of his statements violated their sixth amendment right of confrontation and required a severance. They rely primarily on Bruton v. United States, supra, which held that in a joint trial, where the confession of a defendant was admitted only against him and he did not testify, his co-defendant’s constitutional rights were not sufficiently protected by a cautionary instruction. The Court reasoned:
because of the substantial risk that the jury, despite instructions to the contrary, looked to the incriminating extrajudicial statements in determining petitioner’s guilt, admission of [the] confession in this joint trial violated petitioner’s right of cross-examination secured by the Confrontation Clause of the Sixth Amendment.
391 U.S. at 126, 88 S.Ct. at 1622. The Court focused on the dangers raised
where the powerfully incriminating extrajudicial statements of a code-[969]*969fendant, who stands accused side-by-side with the defendant, are deliberately spread before the jury in a joint trial. Not only are the incriminations devastating to the defendant but their credibility is inevitably suspect, . The unreliability of such evidence is intolerably compounded when the alleged accomplice, as here, does not testify and cannot be tested by cross-examination.
Id., at 135-136, 88 S.Ct. at 1628.
Salters’ statements were incriminating, and he availed himself of his fifth amendment right not to testify. But, unlike the confession in Bruton, Salters’ statements were admissible against all of the defendants under a generally recognized exception to the hearsay rule. Significantly, Bruton expressly reserved this issue:
There is not before us, therefore, any recognized exception to the hearsay rule insofar as petitioner is concerned and we intimate no view whatever that such exceptions necessarily raise questions under the Confrontation Clause.
Id., at 128 n. 3, 88 S.Ct. at 1624. Thus, Bruton does not alone resolve this issue.
In California v. Green, 399 U.S. 149, 90 S.Ct. 1930, 26 L.Ed.2d 489 (1970), the Court addressed the constitutional issue presented by the admission of hearsay in a criminal trial, and sustained a state statute which permitted the introduction of prior inconsistent extrajudicial statements as substantive evidence in a criminal trial. The Court explained :
While it may readily be conceded that hearsay rules and the Confrontation Clause are generally designed to protect similar values, it is quite a different thing to suggest that the overlap is complete and that the Confrontation Clause is nothing more or less than a codification of the rules of hearsay [W]e have more than once found a violation of confrontation values even though the statements in issue were admitted under an arguably recognized hearsay exception .... The converse is equally true: merely because evidence is admitted in violation of a long-established hearsay rule does not lead to the automatic conclusion that confrontation rights have been denied.
Id., at 155-156, 90 S.Ct. at 1933.
The Supreme Court applied this emerging doctrine in Dutton v. Evans, 400 U.S. 74, 91 S.Ct. 210, 27 L.Ed.2d 213 (1970) (plurality opinion). In Dutton, hearsay evidence of the statement of a co-conspirator which incriminated the defendant was admitted and the co-conspirator did not testify. The testimony was admitted pursuant to a state hearsay exception for statements by co-conspirators made after the termination of a conspiracy. Dutton concluded that the application of this exception “in the circumstances of this case did not violate the Constitution.” Id., at 88, 91 S. Ct. at 219. The Court distinguished Bruton on three grounds: (1) Bruton involved a joint trial while the defendant in Dutton was tried alone; (2) Bru-ton involved the ability of jurors to consider the hearsay only against the confessing defendant; and (3) Bruton involved a confession wholly inadmissible against one defendant while the hearsay in Dutton was admissible as to the defendant. The Court discussed a plethora of factors which impelled the conclusion that admission of the accomplice’s hearsay statement did not violate the confrontation clause: (1) the evidence was not “crucial” or “devastating,” but was peripheral; (2) the defendant was not deprived of the right of confrontation on the issue of whether the co-conspirator actually made the statement; (3) the statement contained no express assertion about past fact; (4) the co-conspirator had personal knowledge of the identity and role of the other participants; (5) the possibility that the statement was founded on faulty recollection was remote; (6) the statement was spontaneous; and (7) it was [970]*970against penal interest. The opinion concluded that:
These are indicia of reliability which have been widely viewed as determinative of whether a statement may be placed before the jury though there is no confrontation of the declarant.
Id., at 89, 91 S.Ct. at 220.20
Although many of the “indicia of reliability” in Dutton and the instant case are similar, it is readily apparent that the cases differ in three significant aspects : the instant case was a joint trial, the contested evidence was important, and the hearsay declarant was an accomplice. We conclude, however, that for several reasons these factors do not sufficiently aggravate the circumstances to compel the conclusion that the confrontation clause required severance in this case: The disputed testimony was admissible under a generally recognized hearsay exception as against all of the defendants, and would have been admissible against each of them had they been tried separately. Even if the defendants had been tried separately, Salters most probably would have invoked the fifth amendment. See Gorin v. United States, 313 F.2d 641, 645-646 (1 Cir.), cert, denied, 374 U.S. 829, 83 S.Ct. 1870, 10 L. Ed.2d 1052 (1963). Therefore, little can be made of the theoretical opportunity to cross-examine him if the case had been severed. Thus, the setting of a joint trial may have heightened the impact of the statements, but it in no way affected the “indicia of reliability” which Dutton considered most relevant.
Although the statements undoubtedly had dramatic impact, they were not “crucial” in the sense that they disposi-tively bolstered an otherwise weak case. The prosecution presented substantial eyewitness testimony which incriminated Sarvis and Leonard, which the hearsay statements supplemented.
Since Salters was an accomplice, the reliability of his hearsay declaration was “inevitably suspect.” Bruton, 391 U.S. at 135-136, 88 S.Ct. 1620. Thus, these hearsay declarations were surrounded by less compelling indicia of reliability than those admitted in Dutton. Had these declarations been a singular or critical element in sustaining the government’s burden of proof, their admission in a trial where the defendant could not cross-examine the declarant would raise a serious confrontation clause issue. But in this case, their reliability was bolstered and their importance diminished by the substantial and corroborative eyewitness testimony presented. In the circumstances of this joint trial, admission of Salters’ hearsay declarations did not violate the confrontation clause. We therefore conclude that under Dut-ton, the confrontation clause did not require a severance in this case, even though a severance may not have been improper.
VI.
IMPEACHMENT — DRUG USE.
Sarvis and Leonard further contend that the district court erred in restricting their cross-examination of Curtis Hughes concerning his use of heroin, in forbidding them to rebut Hughes’ testimony on cross-examination with direct extrinsic evidence from his father, and in refusing to allow expert medical testimony regarding the general effects of habitual, drug use on perception. We disagree.
On voir dire, Hughes admitted that he took heroin about once or twice a week, and that this use had continued until the beginning of trial. When asked whether he had taken heroin on the day of the crimes, he replied, “I can’t recall.” At trial defense counsel cross-examined Hughes concerning his drug habit. Hughes’ testimony differed somewhat from his voir dire testimony. He testified that he had not taken drugs on the [971]*971day he observed the crime. He further testified that he had not taken drugs for several months. When defense counsel then attempted to question Hughes concerning the effects of his drug use, the district court sustained the government’s objection, ruling that defense counsel could not pursue that line of questioning unless he first established that Hughes had used drugs on the day he observed the crimes. The further rulings referred to above ensued.
The authorities are in disarray concerning the propriety of impeaching a witness’ credibility by showing drug use:
as to drug addiction to which more social odium has been attached, many decisions allow it to be shown to impeach, even without evidence that it did in the particular case affect truth-telling, although apparently more courts, absent a particular showing of effect on the witness’s veracity, would exclude it. . [T]he excluding courts seem to have the better of the arguments. It can scarcely be contended that there is enough scientific agreement to warrant judicial notice that addiction in and of itself usually affects credibility. Certainly it is pregnant with prejudice. On the other hand, there is an increasing recognition among non-legal authorities that addiction may in various instances be linked with personality and other defects which do bear upon credibility.
McCormick, supra, § 44 (footnotes omitted). See Kelly v. Maryland Casualty Co., 45 F.2d 782 (W.D.Ya.1929), aff’d, 45 F.2d 788 (4 Cir. 1930); 3 A Wigmore, supra, § 934.
This circuit has recognized the propriety of developing the matter of drug addiction for the purpose of attacking, not the addict’s general credibility,21 but his ability and capacity to observe the events in question. United States v. Kearney, 136 U.S.App.D.C. 328, 420 F.2d 170, 173-174 (1969); United States v. Fowler, 151 U.S.App.D.C. 79, 465 F.2d 664 (1972). See Wilson v. United States, 232 U.S. 563, 34 S.Ct. 347, 58 L.Ed. 728 (1914). In Kearney, the court affirmed where the district court had deferred cross-examination on this issue pending establishment of a foundation. The court concluded:
A judge may not fairly block all probing' of an issue like narcotics use by the prosecution’s sole eyewitness to a murder. On the other hand, . the matter of drug addiction, which involves social transgression and the possibility of illegal conduct, is properly approached with awareness of the potential for prejudice of the jury. In some cases the desirable procedure may lie in permitting defense counsel to establish his foundation by questioning the witness out of the hearing of the jury ....
420 F.2d 174. In Fowler, the court reversed a conviction because the district judge had blocked all inquiry into the witness’s drug habit. The court declared that the defendant has a “right to cross-examine . . . as to whether he [the witness] was using narcotics at the time he observed appellant commit the alleged offense.” 465 F.2d 665. Implicit in this holding is the conclusion that this finding is a sine qua non to further cross-examination.
The district court’s ruling on the scope of Hughes’ cross-examination is consistent with the thrust of these cases. It did not prohibit all cross-examination concerning Hughes’ drug habit, but allowed defense counsel the opportunity to establish a foundation consisting of evidence that Hughes had used narcotics on the day he observed the events. Defense counsel was unable to establish this foundation on cross-examination and therefore had no evidentiary ground to sustain the contention that drugs interfered with Hughes’ capacity to observe the events.
[972]*972Perhaps Hughes’ responses concerning his own drug habit were suspect,22 and contradicted to some extent his voir dire testimony. Nevertheless, Hughes’ drug habit was plainly a collateral issue. We would hesitate to establish a rule which would encourage sub-trials on the highly sensitive issue of narcotics use before the jury.23 Therefore, we conclude that the trial judge’s ruling barring defense counsel’s proffer of extrinsic evidence to contradict Hughes’ testimony on cross-examination was correct. See McCormick, supra, § 47; 3A Wigmore, supra, §§ 1000-1007.
Finally, we recognize the desirability of increasing judicial appreciation of the general effects of drug use on perception, memory, and credibility and the knowledge that expert testimony may bring to this troublesome issue. However, we cannot conclude that the district court was in error when it excluded the proffer of such evidence, given the state of the record.
VII.
IMMUNITY.
At the government’s request, the district court granted immunity to witnesses Jones and Hughes pursuant to 18 U.S.C. § 6002 (Supp.1973).24 This statute authorized the court to grant so-called “use-restriction” immunity.25 Because of an error in the order prepared for the district court’s signature, it erroneously purported to grant transactional immunity26 to Jones and Hughes. The government concedes that the district court inadvertently exceeded its statutory authority. Neither defendant objected at trial, Rule 52(b), F.R. Cr.P., but each claims reversible error in what occurred.
Sarvis and Leonard contend that they were prejudicially injured by this excessive grant of immunity, since, they submit, Jones and Hughes might not have testified if they had known that they could legally have the benefit of only use-restriction immunity. For this proposition and for the proposition that they have standing to raise the issue, defendants rely on Ellis v. United States, 135 U.S.App.D.C. 35, 416 F.2d 791 (1969).
We think that defendants’ reliance on Ellis is misplaced. In Ellis, the district court exceeded its judicial powers by granting immunity where it could under law grant none at all. In those circumstances, it was possible that the witness may never have chosen to testify. But here, Jones and Hughes would have been compelled to testify fully, even if the district court had properly restricted its grant to use-restriction immunity. Their only alternative was a contempt [973]*973citation. Jones and Hughes at no time had an option not to testify.
Defendants further argue that since Kastigar v. United States, 406 U.S. 441, 92 S.Ct. 1653, 32 L.Ed.2d 212 (1972) had not been decided at the time of trial, Jones and Hughes might have thought that mere use immunity was unconstitutional, and would therefore not have testified if they had been granted only use immunity. First, no evidence in the record supports this imaginative supposition. Secondly, we cannot discern a grave potential for prejudice or injustice in the proceedings as they transpired. The district court’s erroneous grant of excessive immunity was not plain error which prejudicially impinged upon substantial rights. Rule 52(b), F.R.Cr.P. Before retrial, we assume that the district court will correct its order granting immunity so as to obviate a repetition of this contention. Reversed; new trial granted.