Full opinion text
Affirmed in part, vacated and remanded in part by published opinion. Senior Judge PHILLIPS wrote the opinion, in which Chief Judge WILKINSON and Judge ERVIN joined. OPINION PHILLIPS, Senior Circuit Judge: Richard Tipton, Cory Johnson, and James Roane were tried to a jury on a 33-count indictment charging each with a number of federal crimes, including capital murder, growing out of their concerted drug-trafficking activities, principally in Richmond, Virginia during a several-year period. Each was convicted on multiple charges, including capital murder; each was sentenced to death on one or more of the capital murder charges on which he was convicted and to various terms of imprisonment on other charges. Each has appealed challenging his conviction on various of the charges against him and the sentence(s) of death imposed upon him. Save for the necessity imposed by double jeopardy concerns to vacate their several convictions for drug conspiracy violations under 21 U.S.C. § 846, we find no error requiring reversal or remand among those assigned by appellants and we therefore affirm their respective convictions and sentences in all other respects. The Government has cross-appealed the district court’s order staying execution of the death sentences pending Congressional authorization of the means of execution. We vacate that order and remand for entry of appropriate orders. I. Recounted in summary form and in the light most favorable to the Government, the core evidence revealed the following. Tipton, Roane, and Cory Johnson were principal “partners” in a substantial drug-trafficking conspiracy that lasted from 1989 through July of 1992. The conspiracy’s operations began in Trenton, New Jersey where Johnson and Tipton, both from New York City, became members. In August of 1990, the conspiracy expanded its operations to Richmond, Virginia where Roane joined the conspiracy in November of 1991. The Trenton-based operation came to an end on June 4, 1991 when police confiscated a large quantity of crack cocaine and firearms. In late 1991, the conspiracy’s operations were expanded from the Central Gardens area of Richmond to a second area in Richmond called New-towne. During the period of the conspiracy’s operation, its “partners”, including appellants, obtained wholesale quantities of powdered cocaine from suppliers in New York City, converted it by “cooking” into crack cocaine, then packaged it, divided it among themselves, and distributed it through a network of 3(M0 street level dealers, “workers.” Typically, the appellants and their other partners in the conspiracy’s operations took two-thirds of the proceeds realized from street-level sales of their product. Over a short span of time in early 1992, Tipton, Cory Johnson, and Roane were variously implicated in the murders of ten persons within the Richmond area — all in relation to their drug-trafficking operation and either because their victims were suspected of treachery or other misfeasance, or because they were competitors in the drug trade, or because they had personally offended one of the “partners.” On January 4, 1992, Tipton and Roane drove Douglas Talley, an underling in disfavor for mishandling a drug transaction, to the south side of Richmond. Once there, Roane grabbed Talley from the rear while Tipton stabbed him repeatedly. The attack lasted three to five minutes and involved the infliction of eighty-four stab wounds to Talley’s head, neck, and upper body that killed him. On the evening of January 13, 1992, Tipton and Roane went to the apartment of Douglas Moody, a suspected rival in their drug-trafficking area, where Tipton shot Moody twice in the back. After Moody fled by jumping through a window, both Tipton and Roane pursued. Roane, armed with a military-style knife retrieved from an apartment where the knife was kept for co-conspirator Curtis Thorne, caught up with Moody in the front yard of the apartment where he stabbed him eighteen times, killing him. On the night of January 14, 1992, Roane, Cory Johnson, and a third person retrieved a bag of guns that they had left at an apartment earlier that day. Roane then located Peyton Johnson, another rival drug dealer, at a tavern. Shortly after Roane left the tavern, Cory Johnson entered with another person and fatally shot Peyton Johnson with a semi-automatic weapon. On January 29, 1992, Roane pulled his ear around the corner of an alley, got out of the vehicle, approached Louis Johnson, whom appellant Johnson thought had threatened him while acting as bodyguard for a rival dealer, and shot him. Cory Johnson and co-conspirator Lance Thomas then got .out of Roane’s car and began firing at Louis Johnson. As Louis Johnson lay on the ground, either Cory Johnson or Thomas shot him twice at close range. Louis Johnson died from some or all of these gunshot wounds. On the evening of February 1, 1992, Cory Johnson and Lance Thomas were told that Roane had gone to the apartment of Torrick Brown, with whom Roane had been having trouble. Johnson and Thomas armed themselves with semi-automatic weapons and went to the apartment where they joined appellant Roane outside. The three then knocked on Brown’s door and asked his half-sister, Martha McCoy, if Brown was there. She summoned Brown to the door and Cory Johnson, Roane, and Thomas opened fire with semi-automatic weapons, killing Brown and critically wounding McCoy. In late January, 1992, after being threatened by Cory Johnson for not paying for a supply of crack cocaine, Dorothy Armstrong went to live with her brother, Bobby Long. On February 1, Cory Johnson learned from Jerry Gaiters the location of Long’s house. Thereafter, Tipton and an unidentified “young fellow” picked up Gaiters and Cory Johnson who were then driven by Tipton to a house where the group obtained a bag of guns. After dropping off the unidentified third party, the group proceeded to Long’s house. Upon arriving at Long’s house, Cory Johnson and Gaiters got out of the car and approached the house. While Tipton waited in the ear, Cory Johnson and Gaiters went to the front door. When Long opened the door, Cory Johnson opened fire, killing both Dorothy Armstrong and one Anthony Carter. Bobby Long fled out the front door, but was fatally shot by Cory Johnson in the front yard. In early February 1992, Cory Johnson began to suspect that Linwood Chiles was cooperating with the police. On February 19, 1992, Johnson borrowed Valerie Butler’s automobile and arranged to meet with Chiles. That night, Chiles, Curtis Thorne, and sisters Priscilla and Gwen Greene met Cory Johnson and drove off together in Chiles’s station wagon. Chiles parked the car in an alley, ■ and Tipton soon drove in behind it in another car, got out, and came up alongside the sta-tionwagon. With Tipton standing by, Cory Johnson told Chiles to place his head on the steering wheel and then shot Chiles twice at close range. Additional shots were fired, killing Thorne and critically wounding both of the Greene sisters. The autopsy report indicated that Thorne had been hit by bullets fired from two different directions. Tipton was charged under 21 U.S.C. § 848(e) and 18 U.S.C. § 2 with capital murder for eight of these killings (Talley, Moody, Louis Johnson, Long, Carter, Armstrong, Thorne, and Chiles); Cory Johnson, with seveii (Louis Johnson, Long, Carter, Armstrong, Thorne, Chiles, and Peyton Johnson); and Roane, with three, (Moody, Louis Johnson, and Peyton Johnson). The jury convicted Tipton of six of the eight capital murders with which he was charged under § 848(e) (Talley, Armstrong, Long, Carter, Chiles, and Thorne). One of the other two § 848(e) charges was dismissed (Louis Johnson) and the other resulted in acquittal (Moody). Tipton was also convicted of conspiracy to possess cocaine base with the intent to distribute (21 U.S.C. § 846), engaging in a CCE (21 U.S.C. § 848(a)), eight counts of committing acts of violence (the eight killings charged under § 848(e)) in the aid of racketeering activity (18 U.S.C. § 1959), two counts of using a firearm in relation to a crime of violence or a drug-trafficking crime (18 U.S.C. § 924(c)), and two counts of possessing cocaine base with intent to distribute (21 U.S.C. § 841(a)(1)). The jury convicted Cory Johnson of all seven of the capital murders with which he was charged under § 848(e) (Louis Johnson, Long, Carter, Armstrong, Thorne, Chiles, and Peyton Johnson). He was also convicted of conspiracy to possess cocaine base with the intent to distribute (21 U.S.C. § 846), engaging in a CCE (21 U.S.C. § 848(a)), eleven counts of committing acts of violence (including the seven killings charged under § 848(e)) in aid of racketeering activity (18 U.S.C. § 1959), five counts of using a firearm in relation to a crime of violence or drug-trafficking offense (18 U.S.C. § 924(c)), and two counts of possession of cocaine base with the intent to distribute (21 U.S.C. § 841(a)(1)). The jury convicted Roane of all three of the capital murders with which he was charged under § 848(e) (Moody, Peyton Johnson, and Louis Johnson.) He was also convicted of conspiracy to possess cocaine base with the intent to distribute (21 U.S.C. § 846), engaging in a CCE (21 U.S.C. § 848(a)), five counts of committing acts of violence (including the three killings charged under § 848(e)) in aid of racketeering activity (18 U.S.C. § 1959), four counts of using a firearm in relation to a crime of violence or a drug-trafficking offense (18 U.S.C. § 924(c)), and one count of possession of cocaine base with the intent to distribute (21 U.S.C. § 841(a)(1)). Following a penalty hearing on the capital murder counts, the jury recommended that Cory Johnson be sentenced to death on all of the seven § 848(e) murders of which he had been convicted; that Tipton be sentenced to death for three of the six § 848(e) murders of which he was convicted (Talley, Chiles, and Thorne); and that Roane be sentenced to death for one of the three of which he was convicted (Moody). The district court sentenced Johnson, Tipton, and Roane to death in accordance with the jury’s recommendations pursuant to 21 U.S.C. § 848(Z), and imposed various sentences of imprisonment upon each of the appellants for the several non-capital counts on which they were convicted and for those capital murder counts on which Tipton and Roane had been convicted but were not given death sentences. On appellants’ motion, the district court refused to order execution of the several death sentences on the grounds that Congress had neither directly authorized the means by which the death sentences imposed under § 848 should be carried out, nor properly delegated to the Attorney General the authority to issue the implementing regulations that were invoked by the Government. In consequence, the district court stayed execution of the death sentences it had imposed until such time as Congress had authorized the means of execution. These appeals by Tipton, Roane, and Johnson and a cross-appeal by the Government from the district court’s stays of execution of the death sentences followed. Appellants present some sixty issues for our review. Most are presented as issues common to all; some only in behalf of particular appellants. They pertain to the jury selection process, to the trial proper, and to the death penalty hearing and sentencing phases. Some warrant extended discussion; others, for various reasons, warrant no more than recognition or summary discussion. We will take first the issues jointly and separately presented by the appellants. Lastly, we will consider the Government’s cross-appeal. II. We first consider a number of joint challenges by all the appellants to various aspects of the jury-selection process. A. The principal challenge is to the district court’s having conducted portions of the jury voir dire out of the immediate presence of the appellants. Appellants jointly contend that this violated their constitutional right under the Fifth Amendment and their parallel statutory right under Rule 43, Fed. R.Crim.P., to be personally present throughout the voir dire process. The Government contends in opposition (1) that appellants effectively waived any constitutional or statutory right they possessed to be personally present throughout the process, or (2) that if the right was not effectively waived, any ensuing error was forfeited by the appellants’ failure to object either contemporaneously or by post-verdict motions, so that it is only reviewable for plain error under Rule 52(b), Fed.R.Crim.P., and that under that Rule’s standard this forfeited error does not warrant appellate correction. To address these issues of waiver, forfeiture, and plain error review, a fairly detailed account of the relevant proceedings is required. The issues arose as a result of the district court’s decision to handle the jury selection process in a series of discrete steps designed to accommodate what the district court obviously saw as special difficulties posed by the size of the venire — -250 prospective jurors — and by the capital murder counts. Initially, as a matter of convenience for the prospective jurors, they would be examined in two separate, roughly equal groups, with the second group not required to report until the first group had been preliminarily screened. Preliminary screening of the two groups was intended to yield a group of around 70 prospective jurors who had not been found excusable for various individual reasons or not subject to challenges for cause. From that preliminarily qualified set of venirepersons, the petit jury and alternates would then be chosen by lottery and the exercise of peremptory challenges. The preliminary screening process of the two groups was to be carried out in what developed as three distinct steps. In the first step, general questions would be addressed by the court to the whole group of prospective jurors concerning such generally non-sensitive sources of possible disqualifying bias as knowledge of the case or of the parties, witnesses, or counsel. This would be done in open court, with the various defendants all present with their counsel. If in response to specific questions from the court prospective jurors indicated by standing that a question posed a possible problem they would be called individually to the bench where, with counsel present, they would be further questioned on the matter by the court. In this step of the process, challenges for cause would be ruled upon or granted sua sponte, yielding a reduced set of prospective jurors. That set would then be further screened in a final step designed in particular to explore the sensitive subjects of death-penalty attitudes and possible racial prejudices. This step would be conducted by the judge in chambers with only counsel and individual prospective-jurors present with him. Further challenges for cause would be ruled upon or granted sua sponte during this final step in the screening process, which would yield the final pool of prospective jurors from which the jury would be selected. Jury voir dire proceeded essentially in accordance with this plan. The fact that at two of its proposed steps the process apparently would be conducted out of the immediate presence of the defendants was not, so far as the record shows, raised in advance as a possible problem by the court or any counsel in the case. That there might be a problem was first suggested only after twelve prospective jurors from the first group had been individually questioned by the court at the bench following their indications of problems in response to the first general question put to the group. At that point, counsel for one of the appellants remarked simply, “I would remind [the court] that under Rogers v. United States, [853 F.2d 249 (4th Cir.1988) ], our clients must waive presence.” JA 885. In immediate response, the judge asked, “Does everybody waive presence of their clients?” Id. To this, defense counsel who had first raised the issue remarked, “We better take one second to be sure. This is a capital ease.” Id. The record then indicates that following a conference of unspecified duration between counsel and their respective client-defendants, counsel for each of the appellants in turn stated to the court that his client, by name, waived. Id. The process then resumed according to plan with further questioning at the bench of those prospective jurors whose responses to general questions required further inquiry. During that phase of the process, a significant number of prospective jurors were excused for cause, either in response to challenges by counsel or by the court sua sponte. When this step had been completed and just as in-chambers individual questioning of the remaining unexcused members of the group was about to commence, the courtroom clerk inquired, apparently of defense counsel, “if the defendants can go back to the lock-up or do you want them in the courtroom ... to be available to talk to them if you want?” Roane’s counsel responded, “Just send them back ....,” and Johnson’s counsel added, “They have waived.” Though the record is not clear on the point, it would appear that the defendants were not actually taken from the courtroom at that time, but only later after the in-chambers process had been underway for some time. See JA 1101. During that in-chambers process, the district court concentrated in its questioning, as had been indicated to counsel, on death-penalty attitudes and possible racial or other bias, and routinely allowed Government and defense counsel to pursue limited further examination on those subjects. As a result of that examination, a number of prospective jurors were excused either upon challenge by counsel or by the judge sua sponte because of intimations either of disqualifying death-penalty attitudes (running both ways) or possible racial biases. Although the second group of prospective jurors was brought in and briefly examined in a general voir dire before in-chambers examination of members of the first group had been completed, a sufficient pool of prospective jurors was obtained from the first group to allow the jury to be selected entirely from that pool. This was done, as planned, by the exercise of peremptory challenges to persons successively called to the jury box by lottery. This final step in the process was carried out in open court, with all appellants present and able to consult with counsel. A total of 52 peremptory challenges were allotted to the then four defendants for exercise with respect to the regular jurors and an additional two with respect to four alternates. The upshot, for purposes of the denial-of-presence issue, is that appellants were personally and immediately present during some but not all portions of the overall voir dire process as it involved those prospective jurors from whom the regular and alternate jurors ultimately were selected. Specifically, they were personally and immediately present while the district court was addressing to the whole group general questions respecting possible sources of bias from relationships or knowledge of the ease, and during the final jury selection process involving the exercise of peremptory challenges. They were not immediately present, though in the courtroom, during any of the judge’s examination of prospective jurors at the bench in the presence of their counsel. And they were not present during any of the in-chambers examination of individual prospective jurors. The Confrontation Clause of the Sixth Amendment and the Due Process Clause of the Fifth Amendment together guarantee the right of federal defendants charged with felonies to be present at all critical stages of their trials. Illinois v. Allen, 397 U.S. 337, 338, 90 S.Ct. 1057, 1058, 25 L.Ed.2d 353 (1970) (Sixth Amendment); Snyder v. Massachusetts, 291 U.S. 97, 106-08, 54 S.Ct. 330, 332-33, 78 L.Ed. 674 (1934) (Fifth Amendment). Rule 43(a), Fed. R.Crim.P., deriving from these constitutional guarantees and the even broader common law privilege, see United States v. Gregorio, 497 F.2d 1253, 1257-59 (4th Cir.1974), confers a comparable right to “be present ... at every stage of the trial.” Included is the right to be present at the voir dire and “impaneling of jurors.” Snyder, 291 U.S. at 106, 54 S.Ct. at 332 (dictum); Rule 43(a) (as quoted). The Government does not contend that the appellants’ constitutional and rule-based right did not extend to the specific portions of the voir dire from which they were absent. Instead, as indicated, the Government contends only that any such right as existed was effectively waived by defense counsels’ several in-court announcements of waiver following consultations with their respective clients or that, if it was not waived, any ensuing error, having been forfeited, does not warrant appellate correction as “plain error” under Fed.R.Crim.P. 52(b). Responding to the Government’s claim of waiver, appellants jointly have raised two difficult issues: first, whether under Fourth Circuit precedent the right of presence may ever and by any means be waived in capital cases; second, whether — if waiver is possible in such cases — it may only be effected by a formal in-court proceeding not provided in this case. Because we conclude that even if for either reason no effective waiver occurred here, any ensuing error, having been proeedurally forfeited, does not warrant correction as plain error, we reserve decision on the difficult waiver issues and proceed to the discussion of the plain error basis for our decision. United States v. Olano, 507 U.S. 725, 113 S.Ct. 1770, 123 L.Ed.2d 508 (1993), guides us here, both as to the relationship between waiver of rights and forfeiture of errors at trial, and as to the proper application of Rule 52(b)’s “plain error” limitation on appellate correction (noticing) of forfeited errors. Where a protected trial right has been effectively waived by a defendant, as the Government claims occurred here, all possibility of error respecting that right has been extinguished. Id. at 733, 113 S.Ct. at 1777. But even where a right has not been waived, any entitlement to have error in its denial or abridgement corrected on appellate review may be forfeited by the “failure to make timely assertion of [the] right” at trial. Id. Such a forfeiture, does not, as does waiver, extinguish the error, id., but it does impose stringent limitations, embodied in Rule 52(b), on the power of appellate courts to correct the error. Olano has now instructed, clarifying the matter, that under Rule 52(b) a court of appeals “has authority” to correct forfeited error only if it is “plain” 'and “affects substantial rights,” and even then is “not required to do so” unless the error is one that “causes the conviction or sentencing of an actually innocent defendant” or otherwise “seriously affect[s] the fairness, integrity or public reputation of judicial proceedings.” Id. at 734-36, 113 S.Ct. at 1777-79. Here, where we have assumed for purposes of this case that there was not an effective waiver of the right at issue, there indisputably was, however, a forfeiture of entitlement to appellate correction of any ensuing error in denying or abridging the right. Not only was there no contemporaneous or post-verdict challenge to conducting portions of the jury voir dire outside the immediate presence of the appellants, counsel for each appellant specifically invited the procedure. Proceeding then to the Olano analysis respecting forfeited error, we further assume, without deciding, that error did occur in the form of a “deviation” from the constitutionally-grounded legal rule that presence was required throughout the proceedings at issue. See id. at 732-33, 113 S.Ct. at 1776-77. And, we also assume — as the Government seems to concede — that any such error as occurred was “plain,” in the sense that it is clear on the record that the challenged proceedings were held outside the immediate presence of appellants. This brings us to the question whether the “plain error,” whose occurrence we assume arguendo, affected any “substantial rights” of the appellants. Olano has now instructed that this may ordinarily (and perhaps only) be established by a defendant’s specific showing — the burden being upon him — that the error caused him actual prejudice by affecting the trial outcome. Id. at 734, 113 S.Ct. at 1777-78. But Olano also noted— without deciding — that aside from this most obvious means, there might be forms of forfeited error that, for Rule 52(b) purposes, “affect substantial rights independent of any prejudicial impact,” and still other forms from which prejudice should be presumed where the defendant could not make a specific showing. Id. at 734-35, 113 S.Ct. at 1777-78. As did the Olano Court, we must address all three possibilities, assuming arguendo the existence of the latter two forms of correctable forfeited errors as to which actual prejudice either need not or cannot be proved. See id. at 737-41, 113 S.Ct. at 1779-82. We first consider whether the assumed error here — conducting some phases of the jury voir dire out of the appellants’ immediate presence — is one which could be found to “affect substantial rights independent of any prejudicial impact.” We can reserve, as did the Olano court, the question whether any such category of forfeited plain error does in fact exist. If it does, it seemingly could only involve violations of absolute rights entitled for overarching systemic reasons to absolute enforcement without regard to any demonstrable (or presumed) prejudicial impact on the defendant. See Arizona v. Fulminante, 499 U.S. 279, 309-10, 111 S.Ct. 1246, 1264-65, 113 L.Ed.2d 302 (1991) (defining category of constitutional errors that may not be found harmless because, without regard to actual prejudice, they deprive defendants of “basic protections” of fundamentally fair trial). The constitutional and Rule-based right to presence at all critical stages of trial, though obviously important, is not such an absolute, systemic right. That it is not absolute is of course settled by those Supreme Court decisions, most notably Snyder and Allen, upholding the power of courts in certain circumstances to conduct trials (or portions) in absentia. See also Rushen v. Spain, 464 U.S. 114, 117-18, 104 S.Ct. 453, 454-55, 78 L.Ed.2d 267 (1983) (per curiam) (though right to personal presence is “fundamental,” errors in conducting proceedings out of presence of defendant may be found harmless). To the extent the right is based, as is that claimed here, upon the Due Process Clause (and Rule 43’s codification), it exists only “to the extent that a fair and just hearing would be thwarted by [the defendant’s] absence,” or, put otherwise, it is limited to “those circumstances where a defendant’s presence has a relation, reasonably substantial, to the fullness of his opportunity to defend himself.” Snyder, 291 U.S. at 105-08, 54 S.Ct. at 332-33. The right is thus by definition limited to those circumstances in which absence has a “prejudicial impact” on a defendant’s opportunity effectively to assist in his defense. The courts accordingly have so interpreted it, not as one to be enforced “independent of any prejudicial impact” from a defendant’s absence but as one actually dependent upon the existence of such an impact. See, e.g., United States v. Boone, 759 F.2d 345 (4th Cir.1985) (absence from in-chambers conference between judge and counsel respecting dismissal of juror did not, under the circumstances, frustrate trial’s fairness); United States v. Fontenot, 14 F.3d 1364 (9th Cir.1994) (absence from peremptory challenge conference between judge and counsel not, under the circumstances, prejudicial); cf. Olano, 507 U.S. at 738-39, 113 S.Ct. at 1779 (comparable analysis employed in finding violation of Criminal Rule 24(e) not an “error affecting substantial rights independent of any prejudicial impact”). Accordingly, we conclude that if there be a category of plain errors affecting substantial rights “independent of any prejudicial impact,” absence from portions of a jury voir dire is not among them. We next consider whether, assuming there is a category of plain errors as to which prejudice should be presumed, the assumed error here falls in that category. We conclude that it does not. There may be circumstances of involuntary absence from jury voir dire where prejudice should be presumed, but we think they could only involve absences throughout the entire process. See United States v. Crutcher, 405 F.2d 239, 244 (2d Cir.1968) (complete absence never harmless error). Such an absence almost assuredly deprives a defendant of any effective means of giving informed advice or suggestions to his counsel respecting the ultimate decisions to challenge prospective jurors for cause or peremptorily. But not every absence of whatever nature and duration and during whatever phase of the voir dire necessarily has that effect. Some phases obviously are more critical than others. The potential prejudice from some absences may be relieved by other circumstances. It all depends. Where absence has not been total but only intermittent during the process the courts accordingly have not presumed prejudice but have analyzed the circumstances to determine whether prejudice has been specifically established. See, e.g., United States v. Bascaro, 742 F.2d 1335, 1349-50 (11th Cir.1984) (although peremptory strike phase of voir dire is critical, no prejudice to defendants where attorneys conferred about peremptories outside their presence, but defendants were present both while questioning took place and when strikes actually entered); United States v. Alessandrello, 637 F.2d 131, 137-141 (3d Cir.1980) (absence of defendants from in-chambers questioning of venirepersons respecting pre-trial publicity not prejudicial in view of their presence at substantial part of voir dire and their counsels’ presence during in-chambers proceedings). The absences here plainly were of the intermittent sort, not approaching the total denial of any effective participation in critical phases of the voir dire that might warrant a presumption of prejudice. Accordingly if prejudice is to be found here, it must be by specific showing. Cf. Olano, 507 U.S. at 740-41, 113 S.Ct. at 1781-82 (comparable analysis employed to hold no presumption of prejudice from violation of Criminal Rule 24(c)). Relegated to this means of showing error that “affected substantial rights,” appellants’ burden is to persuade us of actual prejudice, ie., that their absences “affected the outcome of the [trial],” or “probably influenced the verdict[s]” against them either on the guilt or sentencing phases. Olano, 507 U.S. at 734-35, 113 S.Ct. at 1777-78. We conclude that they have not carried that heavy burden. Just how one shows that his absence during portions of a jury selection process actually “affected the outcome of [trial],” or “probably influenced the verdict” against him has apparently never been definitively explored. Literally applied, the standard would seem to require a showing in the end that a defendant’s absence resulted in selection of a jury that probably reached a verdict different from that which would have been reached by a jury selected with benefit of his presence at the times of his absence. If that be the ultimate burden, it is a stringent one indeed — near if not beyond the limits of practical possibility given the variables in the process and evidentiary restrictions. See Fed.R.Evid. 606(b). If we start analysis from the other end, it is obvious that at a very minimum a defendant must show that had he been present a somehow different jury would have been selected. The due process-based right to presence is not violated, hence could not be the source of prejudice, unless one’s presence demonstrably would have made some difference. See Snyder, 291 U.S. at 106, 107, 54 S.Ct. at 332, 333 (no violation, hence no prejudice possible, “when presence would be useless, or the benefit but a shadow”). But, just as surely, showing only that some difference would have resulted could not suffice to show actual prejudice. If no more is shown, for example, than that jurors 1, 3, and 5 would have been excluded, this could not suffice to show that their presence caused the finally unfavorable “outcome.” Something more, for example, that jurors 1, 3, and 5 in the above hypothetical were demonstrably biased, surely must be shown, and even that might not, under all the circumstances, suffice. Fortunately, we need not in this case seek to decide just what showing between these extremes is required. Appellants, relying primarily on their argument of presumed prejudice, offer nothing on actual prejudice beyond the conclusory assertion that “[e]ven if defendants were required to demonstrate prejudice, that prejudice was patent in this case.” Roane Br. 30. This obviously could not suffice to show specific prejudice. Accordingly, we conclude that appellants have not carried their burden to show actual prejudice resulting from their absences during portions of the jury voir dire. Having earlier held that their absences could not constitute error “affecting substantial rights independent of prejudicial impact,” nor “presumed error affecting substantial rights,” we need not consider whether, even if prejudicial, the assumed error so “seriously affect[ed] the fairness, integrity or public reputation of judicial proceedings” that correction was warranted. Olano, 507 U.S. at 741, 113 S.Ct. at 1781. Because appellants have not shown that their absence from portions of the jury voir dire “affected substantial rights,” we conclude that any error involved, having been forfeited, does not warrant correction. B. We next consider appellants’ claim that the district court erred in refusing to permit defense counsel to conduct adequate voir dire and in failing itself to conduct adequate voir dire regarding possible racial bias and attitudes respecting aggravating and mitigating factors if the capital sentencing phase were reached. 1. Appellants moved pre-trial, with supporting affidavits, that defense counsel be permitted detailed participation in jury voir dire questioning on possible racial biases, pointing to the fact that each of the appellants was black and to the pervasiveness in society of racial prejudice. The court denied the motion but invited defense counsel to submit proposed questions pursuant to Fed. R.Crim.P. 24(a). Counsel submitted 62 such questions on such matters as beliefs in the trustworthiness and criminal propensities of black persons, whether the prospective jurors lived in racially separated neighborhoods or attended racially separated churches, and the like. The district court declined to incorporate these questions in its own in-ehambers questioning of individual prospective jurors, and put only a single question respecting their possible racial bias: “Do you harbor any bias or prejudice, racial or otherwise, that would prevent you from being fair to the defendants in this case?” See, e.g., JA 1009. The court then permitted limited follow-up inquiry by counsel depending upon responses made to his general question. JA 1061. Appellants contend that this was insufficient to provide reasonable assurance that if bias did exist, it would be uncovered, as they say was their right. And, they argue that in this case its insufficiency was exacerbated by the fact that the district judge was himself a black person, thereby making the concealment of racial bias more than ordinarily a risk. We disagree and find no error in the district court’s decision (1) not to allow detailed questioning of the type proposed by appellants, whether done by himself or defense counsel; and (2) to limit the questioning on this subject to the general question he put. No question is raised of entitlement to some inquiry into possible racial bias— whether under the Constitution, see Ristaino v. Ross, 424 U.S. 589, 597, 96 S.Ct. 1017, 1021, 47 L.Ed.2d 258 (1976) (constitutionally compelled where racial issues “inextricably bound up with the conduct of the trial”) or under the Supreme Court’s broader supervisory rule for federal courts, see Rosales-Lopez v. United States, 451 U.S. 182, 191, 101 S.Ct. 1629, 1636, 68 L.Ed.2d 22 (1981) (compelled where “circumstances ... indicate ... reasonable possibility that racial ... prejudice might have influenced the jury”). Inquiry was made here; the challenge is only to its confinement to the single question put by the trial judge, with opportunity only for limited followup questioning by counsel. Once the decision has been made to conduct any inquiry into this sensitive matter, the exact nature and scope of that inquiry is committed to the broad discretion of the district court, and is subject to review only for abuse. Rosales-Lopez, 451 U.S. at 189, 101 S.Ct. at 1634-35; Ham v. South Carolina, 409 U.S. 524, 527, 93 S.Ct. 848, 850-51, 35 L.Ed.2d 46 (1973); see also Fed.R.Crim.P. 24(a) (discretion extends to party participation in voir dire). Powerful conflicting considerations inform that discretion. On the one hand, there must be the concern to root out a form of bias that prospective jurors may be particularly reluctant to reveal. See, e.g., United States v. Lewin, 467 F.2d 1132, 1137 (7th Cir.1972). On the other hand, there has to be an equally weighty concern where race is not directly in issue not to overemphasize in jurors’ minds the facts and possible relevance of the racial identities of litigants or witnesses. See Ristaino, 424 U.S. at 596 n. 8, 96 S.Ct. at 1021 n. 8 (danger of creating impression that justice in the courts turns on race or ethnicity); United States v. Barber, 80 F.3d 964, 967, 968 (4th Cir.1996) (en banc) (danger of “diverting] the trial’s focus from the guilt or innocence of the defendant to peripheral factors, such as the defendant’s race ...”). Undoubtedly taking these considerations into account, the Supreme Court has indicated that even where inquiry is constitutionally required because of inextricably involved racial issues, questioning may properly be confined to the sort of single, general question put to jurors here. Ham, 409 U.S. at 525 n. 2, 527, 93 S.Ct. at 849 n. 2, 850-51 (question “Would you fairly try this case on the basis of the evidence and disregarding the defendant’s race,” held “sufficient to focus the attention of prospective jurors on any racial prejudice they might entertain”). In this case, given the critical circumstances that race was not itself an issue and that none of the offenses charged was interracial in nature, we cannot find abuse of discretion in the district court’s decision to confine questioning on racial bias to the general question the court put with opportunity provided for follow-up questioning by counsel. 2. Appellants tendered a set of proposed questions respecting prospective jurors’ attitudes about various possibly mitigating factors as they might influence jurors’ consideration of the penalty phase. They included inquiries into the prospective jurors’ willingness to consider factors such as a defendant’s “deprived, poor background,” “emotional, physical abuse,” “young age,” “limited intelligence,” and “brain disfunction.” The district court declined to incorporate these in its own questioning, and when counsel for appellants attempted to ask these or similar questions, refused to allow them. Appellants claim that this violated their constitutional and rule-based right to a voir dire adequate to assure an impartial jury on the critical capital sentencing issue. We disagree. It is important in assessing this claim to identify the voir dire right at issue. In general terms it is the right, grounded in the Sixth Amendment, to a voir dire adequate to assure a defendant a jury, all of whose members are “able impartially to follow the court’s instructions and evaluate the evidence,” Rosales-Lopez, 451 U.S. at 188, 101 S.Ct. at 1634, here instructions and evidence relevant to imposition of the death penalty. More specifically it is the right to an inquiry sufficient to ensure — within the limits of reason and practicality — a jury none of whose members would “unwaveringly impose death after a finding of guilt” and hence would uniformly reject any and all evidence of mitigating factors, no matter how instructed on the law. Morgan v. Illinois, 504 U.S. 719, 733-34, 112 S.Ct. 2222, 2232-33, 119 L.Ed.2d 492 (1992) (right to such an inquiry established). Just how an inquiry adequate for this specific purpose should be conducted is committed to the discretion of the district courts. The Constitution no more “dictate[s] a catechism” for its conduct than it does for any other subject of required voir dire inquiry. Id. at 729, 112 S.Ct. at 2229-30; Rosales-Lopez, 451 U.S. at 189, 101 S.Ct. at 1634-35; Aldridge v. United States, 283 U.S. 308, 310, 51 S.Ct. 470, 471, 75 L.Ed. 1054 (1931). Obviously, the most direct way to get at the possibility that a prospective juror would always impose death following conviction is to put that very “reverse-Witherspoon ” question directly to him and take it from there. Morgan, 504 U.S. at 724 n. 3, 112 S.Ct. at 2227 n. 3. But, just as obviously, that cannot be the “only means of ensuring ... an impartial jury” on the life-or-death issue. Id. Here, by way of getting at that possible disqualifying bias, the district court first explained to each juror that if guilt of a capital offense was found in a first stage of the trial, the jury would then consider whether to impose the death penalty in a second stage at which the Government would try to convince the jury that aggravating factors warranted death while the defense would try to convince the jury that because of mitigation, death was not appropriate, and that this was then to be decided by the jurors on the basis of that evidence and the court’s instructions on the law. See, e.g., JA 1170-72 (juror Catlett). Against this background, the court then asked each prospective juror: “[D]o you have strong feelings in favor of the death penalty?” See, e.g., JA 1172 (juror Catlett). If the juror answered with an unqualified “No,” the court moved on. E.g., JA 1172 (juror Catlett). If, however, the prospective juror gave any answer other than an unqualified “No” the court then asked directly whether “you would always vote to impose the death penalty in every case where a defendant is found guilty of a capital offense.” See, e.g., JA 1205 (juror Coleman). By this course of inquiry the district court obviously considered that the question, “Do you have strong feelings in favor of the death penalty?” was sufficient for the purpose if it received an immediate and unqualified “No” in response. Presumably, the thought was that except where the response was hesitant or equivocal, a direct “reverse-Witherspoon ” question, such as “Does this mean that you would not always vote to impose death following conviction?” would be at least an unnecessary redundancy and possibly an imprudent risk of encouraging an opposite partiality. That only if “strong feelings in favor” were revealed need there be further inquiry into just how strong; that a person not strongly in favor of the death penalty necessarily is not one who feels so strongly that he will always impose the death penalty no matter what the circumstances. Cf. Lockhart v. McCree, 476 U.S. 162, 170 n. 7, 106 S.Ct. 1758, 1763 n.7, 90 L.Ed.2d 137 (1986). (“State may challenge for cause prospective jurors whose opposition to the death penalty is so strong that it would prevent [their impartiality].”) We cannot say that such a view of the matter is so implausible as to make the inquiry inadequate as a matter of law. An inquiry which more explicitly embodies the “reverse-Witfe-erspoon ” question might give greater assurance — might in some eases be more prudent — but that is not the question for us. Under all the circumstances — the question’s logical adequacy to address the ultimate issue of death-penalty impartiality, the context in which it was put, the court’s repeated admonitions that under the law consideration of mitigating factors would be required — we could not find constitutional abuse in the court’s confinement of its “life-qualifying” inquiry in this way. We are bolstered in this conclusion by the fact that in this case appellants never requested that a further specific “reverse-Witherspoon ” question be put to those prospective jurors who already had responded unequivocally that they had no strong feelings in favor of the death penalty. The right to any inquiry on this subject is dependent upon request, Morgan, 504 U.S. at 736, 112 S.Ct. at 2233, and though appellants requested detailed questioning about specific mitigating factors, they neither requested that a specific “reverse-Witherspoon” question be put to any prospective juror nor objected contemporaneously to the district court’s mode of inquiry as to basic death penalty attitudes. From what has been said, it follows that the district court’s refusal to question or allow detailed questioning about specific mitigating factors did not constitute an abuse of discretion. The undoubted fact that such detailed questioning might have been somehow helpful to appellants in exercising peremptory challenges does not suffice to show abuse of the district court’s broad discretion in conducting the requisite inquiry. See Mu’Min v. Virginia, 500 U.S. 415, 424-25, 111 S.Ct. 1899, 1904-05, 114 L.Ed.2d 493 (1991). Because we conclude that the district court’s inquiry into death penalty attitudes was sufficient to cull out any prospective juror who would always vote for the death penalty whatever the circumstances, we cannot find error in the court’s refusal to conduct or allow further detailed inquiry about specific mitigating factors. C. Appellants jointly contend that three prospective jurors, Beazley, Ellis, and Gains-burg, were erroneously removed for cause by the district court in violation of appellants’ rights under Witherspoon v. Illinois, 391 U.S. 510, 88 S.Ct. 1770, 20 L.Ed.2d 776 (1968), and its progeny. We disagree. The Sixth Amendment’s guarantee of an impartial jury is violated by the exclusion of a prospective juror simply because he expresses some reservations about imposing the death penalty in any case. Id. at 520-23, 88 S.Ct. at 1776-78. It is not violated, however, by the exclusion of a juror whose expressed reservations are such as to make him “irrevocably committed to ... vote against the death penalty regardless of the facts and circumstances” of a case, id. at 522 n. 21, 88 S.Ct. at 1777 n. 21, or, short of that, such as to “prevent or substantially impair the performance of his duties as a juror in accordance with his instruction and his oath.” Wainwright v. Witt, 469 U.S. 412, 424, 105 S.Ct. 844, 852, 83 L.Ed.2d 841 (1985) (quoting Adams v. Texas, 448 U.S. 38, 45, 100 S.Ct. 2521, 2526, 65 L.Ed.2d 581 (1980)). Whether such reservations as are expressed cross the line into “irrevocable commitment” or “substantial impairment” is perforce committed in the first instance to trial court discretion based upon the voir dire inquiry. Because what is being inquired into is a state of mind whose determination turns largely on assessments of demeanor and credibility, matters peculiarly within the province of trial judges, our review of those determinations is appropriately most deferential. Witt, 469 U.S. at 428, 105 S.Ct. at 854; Keeten v. Garrison, 742 F.2d 129, 135 (4th Cir.1984); Briley v. Bass, 750 F.2d 1238, 1246 (4th Cir.1984). Here, we can find no abuse of discretion or error of law in the district court’s exclusion of these three prospective jurors. Following the initial expression by each of some degree of reservation, each was extensively questioned further by the court and by opposing counsel. Each responded to some extent ambiguously as to the depth and likely consequence of his or her reservation. In the end, however, each expressed reservations, never retracted, sufficient to warrant the district court’s determination that they would substantially impair the juror’s performance of duty to vote for the death penalty if the evidence and law so dictated. Prospective juror Ellis, asked at the outset by the court whether on the basis of the evidence and the court’s instructions she could “make an objective, reasoned and fair decision about imposing the death penalty” responded “I don’t know,” and to the court’s follow-up question, “What gives you pause?” responded “I’m not sure at this time if I could give the death penalty.” Later, in response to the prosecution’s question whether her personal opinion could “substantially impair [her] service as a juror,” she answered “I would hope not,” and to a reiterated, “But could it?” responded, “It might.” Still later, in response to defense counsel’s question whether she could imagine cases “where she could contemplate imposing the death penalty” she stated that “there are some cases where I could,” and to a follow-up question whether in such cases her “personal feeling would get in the way” answered “No.” JA 1351-57. This simply left the court with facially ambiguous and arguably contradictory indications of the depth of her reservations. In those circumstances we have felt obliged to “rely on the trial court’s discretion in determining which responses best manifested the juror’s true opinions.” Briley, 750 F.2d at 1246. We so conclude as to the court’s removal of prospective juror Ellis. The same analysis applies to the Court’s removal for cause of the other two prospective jurors. Prospective juror Beazley first responded to the court’s question whether he would be able to impose the death penalty “disregarding any views that you might have as to what the law is or ought to be” by saying, “I doubt it,” and explained, “If I get on the jury and I have to give a death sentence, I don’t think I could live with it ... I really don’t.” Under probing by defense counsel he later said “yes” to questions whether he could “imagine” a crime sufficiently severe that he would impose the death penalty, and whether the multiple murders charged in this case would “in your estimation justify it.” But when in conclusion he was asked “what about a cold-blooded murder for profit?” his final response on the subject was, “I feel yes, but like I say, I’m just a nervous person. If I could live with it after I done it, I just wonder.” JA 1063-65. We cannot quarrel with the district court’s obvious determination that the first and last expressions by this venireman “best manifested the juror’s true opinion.” Briley, 750 F.2d at 1246. So also, with respect to prospective juror Gainsburg. After indicating some reservations about imposing the death penalty in any but “a very limited number of situations,” he responded to the court’s question whether in this case he could make “a fair, reasoned, objective determination” whether to impose the penalty by saying, “I would like to say yes. But I really suspect that my prejudices might to some extent affect my decision.” Though later, under questioning by defense counsel, he stated that he “absolutely would consider it,” he immediately qualified this by saying, “But I honestly believe that my decision would be based on my own biases and prejudices.” And, when the court then asked if by this response he was saying that he didn’t believe he could follow the court’s instructions if they were “not in sync” with his biases and prejudices, he responded, “I suspect that’s what I’m telling you.” JA 1401-05. The court did not err in excluding venireman Gainsburg based on the course of inquiry. D. Appellants’ final joint challenge to the jury selection process is that in exercising its peremptory strikes the prosecution impermissibly struck a disproportionate number of women, thereby violating appellants’ constitutional right as recognized in J.E.B. v. Alabama ex rel. T.B., 511 U.S. 127, -, 114 S.Ct. 1419, 1430, 128 L.Ed.2d 89 (1994) (equal protection under Fourteenth Amendment); see United States v. Lane, 866 F.2d 103, 104 n. 1 (4th Cir.1989) (Fifth Amendment provides comparable rights in federal prosecutions). Appellants did not contemporaneously object on this basis to the prosecution’s exercise of peremptory challenges, and the Government contends that this forecloses them on the issue in this court. Ordinarily it would, see Clark v. Newport News Shipbuilding & Dry Dock, 937 F.2d 934, 939-40 (4th Cir.1991), but appellants point out that J.E.B. was only decided after completion of the trial in this case and that at that time the rule in this circuit was that Batson v. Kentucky, 476 U.S. 79, 106 S.Ct. 1712, 90 L.Ed.2d 69 (1986) (race-based peremptory challenges prohibited), did not extend to gender-based challenges, see United States v. Hamilton, 850 F.2d 1038, 1041-12 (4th Cir.1988), so that their failure to object contemporaneously must be excused. To this, the Government responds that the failure is not excused, notwithstanding Hamilton, because at the time of trial, there was a direct conflict on the issue within the circuits and among the state courts, see, J.E.B., 511 U.S. at - n. 1, 114 S.Ct. at 1422 n. 1, so that appellants were obliged under Fed.R.Crim.P. 51 to object in order to preserve the claim. Without accepting the Government’s position on procedural default, we nevertheless conclude that the bare showing of gender discrimination first attempted on this direct appeal does not suffice either to allow first instance consideration by this court (as appellants concede), nor to warrant a remand for first instance consideration by the district court. III. We next address a number of challenges, some joint, some separate, to various trial court rulings at the guilt phase of the trial. A. Based on an underlying contention that the evidence on the conspiracy count tended to prove three separate conspiracies rather than the single one charged, appellants jointly and individually challenge a number of related district court rulings which denied (1) Roane’s motions for severance and for an in limine exclusion of any evidence against him except that related to the Newtowne phase of any concerted drug trafficking activities, (2) related motions for instructions limiting the evidence properly to be considered against particular appellants, and (3) motions for a multiple-conspiracy instruction. We find no reversible error as to any of these. Critical to all of these challenges is the argument that the evidence could have supported findings only of three separate conspiracies, and not of the single one charged. Specifically, it is contended that the evidence only supported findings of an original conspiracy centered on Trenton, New Jersey involving the “New York Boyz” group that included Tipton and Johnson, a separate conspiracy centered on the Central Gardens area of Richmond in which only Tipton and Johnson of the appellants were involved, and another separate conspiracy centered on the Newtowne area of Richmond in which all three appellants — Roane for the first time — were involved. We disagree with this critical contention; the evidence supports the jury’s finding of the single conspiracy charged and of Roane’s connection to it. The indictment charged that “from on or about January, 1989, ... and continuously thereafter up to and including the filing of this indictment,” appellants and others conspired to possess with intent to distribute and to distribute cocaine base “in the Eastern District of Virginia and elsewhere.” The evidence amply supports the jury’s finding that such a single conspiracy existed and that each applicant was a participant in that conspiracy. In summary, the evidence was sufficient to show the following: Such a conspiracy originated in the Trenton, New Jersey area in 1989, involving as its core members a group known as the “New York Boyz” and including as members Appellants Tipton and Johnson and co-defendant Lance Thomas. In 1991, law enforcement efforts resulted in a cessation of the conspiracy’s operations in the Trenton area but not in its continued existence and operation elsewhere. At that time, some members of the conspiracy ceased their participation while some went to New York City and others, including Appellants Tipton and Johnson, and Lance Thomas, went to Richmond. Earlier, while still engaged in the Trenton operation, Tipton had organized a Central Garden operation in Richmond that expanded the conspiracy’s geographical area while continuing to use its established mode of obtaining, processing, and distributing its drug product. The Central Garden operation was supplied from the New York drug source that supplied the Trenton-based operation. Under Tipton’s leadership, it employed the same methods of intimidation and violence to dominate the crack cocaine trade in this new market area of its operation. Shortly after the Central Garden operation commenced, “Hess,” one of the New York Boyz group, came from New York to act as an enforcer for the operation; later, he returned to New York to deal with “trouble” resulting from a police raid on a house used by the New York Boyz. Appellant Johnson came from.the New York area to the Richmond area in the summer of 1990 for the specific purpose, according to Tipton, of making sure that the losses taken in earlier operations were not repeated there. Throughout the Richmond-based operations, Tipton, as key man of the conspiracy’s operations there, asserted his ability to call on the New York Boyz group — who remained in the New York area — to assist the Richmond operation. Seeking to further expand the conspiracy’s operations in the Richmond area, Tipton directed the development of another distribution network in the Newtowne area of Richmond. By late 1991, it was the main focus and the most productive area of the conspiracy’s operations in the Richmond area. It was during the early stages of this new market area’s development that Appellant Roane joined the conspiracy. A cousin of Tipton’s who “had a spot” in Newtowne, Roane was brought in at Tipton’s instigation in the Fall of 1991 soon after being released from prison, to help develop that new area. From that point on, he participated as a full “partner” with Tipton, Johnson, and other conspiracy leaders in the ongoing operations of the conspiracy. Appellants emphasize the evidence that membership in the groups participating in the concerted drug trafficking activities in the Trenton and Richmond areas shifted over time and that the activities were widely separated geographically and in time. That evidence was of course relevant to the ultimate factual issue whether the single conspiracy charged did exist, but it surely did not prevent a properly supported finding that it did. See United States v. Banks, 10 F.3d 1044, 1053-54 (4th Cir.1993) (single conspiracy properly found despite looseness of organizational structure, changing membership, shifting roles of participants, limited roles and knowledge of some members). Once that underlying contention is rejected, all the claims of error dependent upon it fail. With its rejection, no appellant has any basis for claiming unfair prejudice from the introduction and consideration against him of any evidence about any activities of others in furtherance of the single conspiracy charged. The basic rule is that persons who have been indicted together, particularly for conspiracy, should be tried together. United States v. Brooks, 957 F.2d 1138, 1145 (4th Cir.1992). Once the scope of that conspiracy is established, one’s having come late to or having varied his level of participation in it from time to time puts him in a position “no different from that of any co-conspirator who claims to be prejudiced by evidence that goes to the activities of co-conspirat