A jury convicted the defendants, David Scott, Carl Buchholz and Gregory Sump-ter, of possession with intent to distribute marijuana in violation of 21 U.S.C. § 841. Scott and Buchholz also were charged with, and convicted of, carrying a firearm during a drug trafficking offense, in violation of 18 U.S.C. § 924(c). The defendants now appeal their convictions on numerous grounds. For the reasons set forth in the *732 following opinion, we affirm the judgments of the district court.
I
BACKGROUND
A. Facts
In the summer of 1996, Chad Little and friends, Tommy Smith and David Scott, discussed the difficulty of obtaining marijuana in the St. Louis area. Little agreed' to contact a college friend who might be able to assist them in procuring marijuana for their own use and for resale. Little’s college friend, unbeknownst to Little, was cooperating with law enforcement agents and put Little in touch with undercover officer Kelly Cain of the Drug Enforcement Administration. Little then engaged in ongoing negotiations with Cain to obtain up to 300 pounds of marijuana for redistribution in the St. Louis area.
To fund the venture, Little enlisted the assistance of Scott, Sumpter and Buchholz. For his part, Little contributed $500 and a motorcycle toward the purchase. The remainder of the purchase price was supplied by Scott ($500), Sumpter ($20,000) and Scott Carver ($3,000). Also, as part of the purchase arrangements, Little, Scott and Buchholz were to carry firearms to protect both the collateral and the contraband. On May 6,1997, Little, Scott, Bueh-holz and Sumpter traveled from St. Louis, to Lincoln, Illinois to purchase the marijuana. Upon arriving in Lincoln and presenting the money and other items, all were arrested.
After their arrest, both Buchholz and Sumpter made statements concerning the nature of the arrangement. Specifically, Buchholz stated that he had assisted Little in renting a trailer to transport Little’s motorcycle and that he knew that Little was going to use the motorcycle as partial payment for a marijuana deal. Buchholz, however, did not indicate when he had learned that the motorcycle would be used to purchase marijuana. According to the interviewing officers’ testimony, Buchholz also said that Little had told him that he (Buchholz) might be needed to drive Little’s vehicle and that his role was to provide security.
Sumpter told the interviewing officers that Little had been talking about the marijuana deal for about a week, that the deal was for a few hundred pounds, and that the motorcycle and cash were to be traded for marijuana. Sumpter stated that his role was to inspect the marijuana. Although Sumpter was unsure of his compensation for these efforts, he understood that Little would “take care of him.” Tr. 766.
All of the defendants subsequently were charged with possession with intent to distribute marijuana; Buchholz and Scott also were charged with carrying a firearm during a drug trafficking offense. Little pleaded guilty to the charge, as well as federal money laundering charges pending in Missouri. The remaining defendants, Scott, Buchholz and Sumpter, pleaded not guilty and proceeded to trial.
B. District Court Proceedings
1. Voir dire
It came to the attention of the district court that Juror 99 had expressed concern that the defendants had access to the information provided on the juror questionnaires. Counsel for the defendants requested that the court question Juror 99 about her comments, outside the presence of the other jurors. The district court granted the defendants’ request. During the questioning, Juror 99 stated that she did not “think concern is the right word,” but rather was curious as to “[w]hy the defendants were able to look through our *733 questionnaires.” Tr. 190. She further stated that the court had satisfied her concern or curiosity, and she believed that she could be fair and impartial.
Following the juror’s questioning, counsel for the defense, who had exhausted their allotment of peremptory challenges, requested that the juror be removed for cause. The district court first intimated that it might grant the request if the defendants would agree to a trial by eleven as the jury pool had been exhausted. However, on reexamination, the district court determined that juror curiosity did-not support a “for cause” challenge. Consequently, the court denied the request.
2. Witness testimony
During the trial, the key evidence was provided by Little and several drug enforcement agents. As a result, the primary defense strategy was to attack the credibility of Little and the agents to whom Buchholz and Sumpter had made their statements.
To counter the attacks on Little’s credibility and the suggestions that he was biased in favor of the Government, the Government introduced the testimony of Special Agent William Scheitlin of the Internal Revenue Service concerning Little’s cooperation in an unrelated drug and money laundering investigation in St. Louis, Missouri (“the St. Louis case”). 1 Special Agent Scheitlin testified, over objection, that Little had cooperated in the prior case and that, due in part to Little’s cooperation, several persons were indicted and one of the main targets of the investigation had pleaded guilty to various criminal offenses. Immediately following Special Agent Scheitlin’s testimony, the district court gave the following instruction:
Ladies and gentlemen of the jury, the testimony of this officer that as a result of Mr. Little’s assistance certain individuals entered pleas of guilty in the Missouri investigation does not give any rise to any inference that these Defendants here on trial are guilty. [T]he testimony is merely admitted to substantiate some of what Mr. Little has testified to. Again, it does not give rise to any inference that these defendants are, in fact, guilty. .
Tr. 724-25.
The defendants also mounted an attack on the credibility of the arresting officers. Specifically, the defense suggested that the substance of the statements allegedly made by Buchholz and Sumpter came from information that the arresting officers had received in an earlier briefing about the transaction, and that the statements were not the words of the defendants. The defense also focused on the officers’ questioning methods, their motivation in failing to use audio or visual recording devices, and their intent in discarding their original notes after completing the final report.
3. Instructions
At the instruction conference, the defendants tendered Pattern Federal Jury Instruction for the Seventh Circuit 5.11 (“Pattern Instruction 5.11”). Pattern Instruction 5.11 states:
(a)
A defendant’s presence at the scene of a crime and knowledge that a crime is being committed is not alone sufficient to establish the defendant’s guilt.
[A defendant’s association with conspirators [or persons involved in a criminal enterprise] is not by itself sufficient *734 to prove his/her participation or membership in a conspiracy [criminal enterprise].]
(b)
If a defendant performed acts that advanced a criminal activity but had no knowledge that a crime was being committed or was about to be committed, those acts alone are not sufficient to establish the defendant’s guilt.
Pattern Fed. Jury Instruction for the 7th Cir. 5.11. The court believed that either the first or second paragraph of (a) was appropriate, but not both. As a compromise position, the district court gave as its instruction the first paragraph of (a) and all of (b).
4. Closing arguments
Prior to closing argument, the Government sought permission from the district court to argue to the jury that Buchholz’s and Sumpter’s statements to law enforcement agents were confessions. The defendants objected, but the district court allowed the Government to make the argument to the jury. The defendants, stated the court, were free to argue the opposite. During closing arguments, therefore, the Government’s attorney attempted to characterize the statements as confessions.
The Government also spent some time during closing argument addressing the defendants’ attack on the credibility of Little and of the law enforcement officers who testified. With respect to the officers, the Government argued:
You can take — certainly take all three of the defense closings that you’ve heard today, lump them in to two areas: incessant reference to Mr. Little, and out and out perjury by four law enforcement officers who testified before you. Those are the two areas that have been referred to over and over and over and over again.
The clear implication from [Sumpter’s counsel’s] closing, which has stemmed from the very beginning, from the opening, before any of these witnesses even testified, was that Inspector Eck and Officer Burke came in here, committed crimes by perjuring themselves.
Tr. 1322. The defense did not object to any of these statements.
The jury subsequently found the defendants guilty as charged on all counts.
II
DISCUSSION
A. Testimony of Special Agent Scheit-lin
On appeal, the defendants first argue that the district court allowed the Government to engage in impermissible “bolstering” of Little’s testimony that deprived them of a fair trial. Specifically, the defendants’ question the district court’s admission of testimony by Special Agent Scheitlin concerning Little’s cooperation in the St. Louis case; according to the agent’s testimony, Little’s testimony in the St. Louis case assisted in obtaining convictions and indictments against those involved. The district court found controlling this court’s decision in
United States v. Lindemann,
“ ‘Bolstering’ is the practice of offering evidence solely for the purpose of enhancing a witness’s credibility before that credibility is attacked.”
Lindemann,
*735
In Lindemann, we addressed the operation of bolstering and rehabilitation as they apply to the testimony of a cooperating witness. There, Lindemann had suggested that a witness, Burns, “falsely implicated [Lindemann] to obtain a plea deal,” that is, that Burns was biased in favor of the Government. Id. We held that, when the defense makes such an attack, “the government [is] entitled to introduce evidence to rehabilitate [the witness] on the issue.” Id. Furthermore, because the Federal Rules of Evidence do not consider bias a collateral issue, we held that “it was permissible for evidence on this issue to be extrinsic in form.” Id. The only limitations, therefore, on this type of testimony was the relevance standard set forth in Federal Rule of Evidence 402 2 and the prejudice standard set forth in Federal Rule of Evidence 403. 3 Applying these standards to Burns’ testimony, we stated:
Here we conclude that the admission of evidence regarding Burns’ cooperation in other cases was relevant. The evidence specifically rebutted the allegation that Burns was biased out of self-interest in Lindemann’s case: Burns’ successful participation in numerous other cases meant that at the time he was negotiating over his plea deal, he had lots of information to use as bargaining chips. That fact was relevant under the standards of [Federal Rule of Evidence] 402 because it made less probable the assertion that Burns was lying in Linde-mann’s case out of self-interest. Finally, the district court immediately warned the jury that it was not to infer Linde-mann’s guilt from the fact that other indicted individuals had pleaded guilty. Thus the evidence was used only to assess Burns’ credibility, not as evidence of Lindemann’s guilt.
Id. at 1243-44.
In
United States v. Curry,
[t]hat is enough to create the multiple “chips” to which Lindemann referred. In addition, [the witness’] history of successful cooperation was relevant evidence under the standards of Federal Rule of Evidence 402 because the fact that she had cooperated against Pulley, who then pleaded guilty, made it more probable that she was telling the truth about Curry.
Id.
We believe
Lindemann
and
Curry
control the present case. Here, Little had information to provide the Government with respect to these defendants and to the defendants in the St. Louis case; consequently, Little had multiple “bargaining chips” to use in his plea negotiations. This fact, introduced through Special Agent Scheitlin, made it less probable that Little was lying out of self-interest against the defendants.
See Lindemann,
The defendants acknowledge the holdings of
Lindemann
and
Curry
but claim that they .are distinguishable from the present case on several grounds. First, the defendants state that in
Lindemann
the witness testified to his own prior cooperative efforts whereas here an agent was called to testify about Little’s cooperation. “This is an important difference ...,” claim the defendants, “because the basis for allowing the testimony about other cooperation is related to the cooperating witness’ state of mind.” Appellants’ Br. at 27. We do not believe that this is a material distinction. In
Lindemann,
we approved the use of “extrinsic” evidence to establish a witness’ credibility after attack; we did not limit it to extrinsic evidence from the witness himself.
Lindemann,
The defendants also attempt to distinguish
Lindemann
on the ground that
Lin-demann
involved the cooperation of the witness in the investigation of the same scheme or conspiracy that led to charges against the defendant. Again, there is no basis in
Lindemann
or
Curry
for drawing this distinction. Those cases hold that the evidence of cooperation in other cases is relevant “because the witness’s ‘successful participation in numerous other cases meant that at the time he was negotiating over his plea deal he had lots of information to use as bargaining chips’ and thus was less likely to be lying in [this particular] case out of self-interest.”
Curry,
The defendants further urge that the evidence was not valuable because Little already had served his sentence in the St. Louis case, but had not been sentenced on the drug and firearm charges. Consequently, they maintain, there was nothing about his prior cooperation that made it less likely that he was lying about the defendants. Again,
Lindemcmn
and
Curry
do not admit of such a distinction. In
Lindemcmn,
we stated that “Burns’ successful participation in numerous other cases meant that
at the time he was negotiating over his plea deal,
he had lots of information to use as bargaining chips.”
Lindemann,
Because the evidence was admissible and not unduly prejudicial, we do not believe the district court abused its discretion in admitting Special Agent Scheitlin’s testimony. However, even if we had reached the opposite conclusion, any error was harmless. Here, as in
Curry,
“[t]he evidence against [the defendants] was overwhelming, and there were a host of corroborating witnesses whose testimony would have helped the jury to evaluate [Little’s] credibility.”
Curry,
B. Instructional Error
The defendants next focus on alleged instructional error. In the district court, the defendants tendered Pattern Instruction 5.11, which states:
(a)
A defendant’s presence at the scene of a crime and knowledge that a crime is being committed is not alone sufficient to establish the defendant’s guilt.
[A defendant’s association with conspirators [or persons involved in a criminal enterprise] is not by itself sufficient to prove his/her participation or membership in a conspiracy [criminal enterprise].]
(b)
If a defendant performed acts that advanced a criminal activity but had no knowledge that a crime was being committed or was about to be committed, those acts alone are not sufficient to establish the defendant’s guilt.
*738 The district court did not believe that all of Pattern Instruction 5.11 was warranted. It therefore agreed to give the “mere presence” portion of paragraph (a) together with paragraph (b). The defendants maintain, however, that the district court’s failure to include the second paragraph of (a), the “mere association” instruction, deprived them of a fair trial.
With respect to a district court’s duty to give a particular jury instruction, this court has stated:
It is the well-settled law of this Circuit that a defendant is entitled to a jury instruction on his or her particular theory of defense if: “(1) the instruction represents an accurate statement of the law; (2) the instruction reflects a theory that is supported by the evidence; (3) the instruction reflects a theory which is not already part of the charge; and (4) the failure to include the instruction would deny the appellant a fair trial.”
United States v. Linwood,
Evaluating the instruction according to these standards, we find no misstep on the part of-the district court. There is no question that paragraph two of Pattern Instruction 5.11(a) represents an accurate statement of the law.
See, e.g., United States v. Percival,
The “mere association” instruction is designed to inform the jury that guilt should not follow from one’s association with those who commit crimes; guilt may only be found when the defendant knowingly participated in the criminal activity. In this case, the instructions adequately apprised the jury of this principle. The instructions given to the jury made it clear both that the defendants must have engaged in the conduct knowingly, and that the determination of knowing participation must be individual to each defendant. Specifically, the district court charged that the jury must find that “the defendants knowingly or intentionally attempted to possess the marijuana.” R.91, Government’s Inst. 22. “To ‘attempt,’ ” the court continued, “means that the defendants knowingly took a substantial step toward the commission of the offense with the intent to commit that offense.” Id., Gov *739 ernment’s Inst. 24. The aiding and abetting instruction also spoke to the knowledge requirement; it stated: “Any person who knowingly aids or abets the commission of a crime is guilty of that crime. However, that person must knowingly associate himself with the criminal venture, participate in it, and try to make it succeed.” Id., Government’s Inst. 31. “[Kjnowingly,” the jury was informed, meant that the “defendants realized what they were doing and were aware of the nature of their conduct, and did not act through ignorance, mistake or accident.” Id., Government’s Inst. 28. Consequently, the court further instructed, “[i]f a defendant performed acts that advanced a criminal activity but had no knowledge that a crime was being committed or was about to be committed, those acts alone are not sufficient to establish the defendant’s guilt.” Id., Defendant’s (Scott) Inst. 1 (as modified).
The district court also took pains to ensure that each defendant’s conduct was evaluated separately and that the acts of one were not imputed to the other. It informed the jury that it “must give separate consideration both to each count and to each defendant.” Id., Government’s Inst. 21. The court continued:
You must consider each count and the evidence relating to it separate and apart from every other count.
You should return a separate verdict as to each defendant and as to each count. Your verdict of guilty or not guilty of an offense charged in one count should not control your decision as to that defendant under any other count.
Id.
We believe that these instructions, taken together, accomplished the same function as the “mere association” instruction. They told the jury that it was not enough that the defendants were present at a crime scene or were unwitting participants in a criminal activity; they were guilty only if they each knowingly participated in some part of the criminal act. 6
C. Prosecutorial Misconduct
1.
The defendants next maintain that several of the Government’s statements in closing arguments constituted prosecutorial misconduct that resulted in, the defendants being denied a fair trial. The defendants believe that the Government’s argument posed an improper alternative to the jury: In order to convict the defendants, the jury had to find that the investigating officers committed perjury. Specifically, the defendants point to two sections of the Government’s closing argument, which states:
You can take-certainly take all three of the defense closings that you’ve heard today, lump them in to two areas: incessant reference to Mr. Little, and out and out perjury by four law enforcement officers who testified before you. Those are the two areas that have been referred to over and over and over and over again.
*740 The clear implication from [Sumpter’s counsel’s] closing, which has stemmed from the very beginning, from the opening, before any of these witnesses even testified, was that Inspector Eck and Officer Burke came in here, committed crimes by perjuring themselves.
Tr. 1322.
Usually, in reviewing improper comments by a prosecutor, this court undertakes a two-step inquiry. “[W]e first determine if the comments, looked at in isolation, were improper.”
United States v. Morgan,
The defendants maintain that the Government’s argument in this case is indistinguishable from the argument we found problematic in
United States v. Vargas,
Even assuming that the testimony of the prosecution and defense witnesses contained unavoidable contradictions, it of course does not follow as a matter of law that in order to acquit Vargas the jury had to believe that the agents had lied. If the jurors believed that the agents probably were telling the truth and that Vargas probably was lying or even if the jury was convinced that all of the agents save Garcia were telling the truth and thought that Garcia probably was telling the truth it would have been proper to return a verdict of not guilty because the evidence might not be sufficient to convict [the] defendant beyond a reasonable doubt. To tell the jurors that they had to choose between the two stories was error.
Id.
We believe that the remarks made by the prosecution in this case are not equivalent to those made in
Vargas.
In the present case, the Government’s attorney argued that “[t]he clear implication from [the defense] closing, ... was that Inspector Eck and Officer Burke came in here,
*741
committed a crime by perjuring themselves,” Tr. 1322, and that there were “suggestions” that the officers falsified the report and committed perjury, Tr. 1327-28. However, the prosecutor here stopped short of giving the jury the ultimatum presented to the jury in Vargas: The prosecutor did not tell the jury that, if they returned a verdict of not guilty, they had to conclude that the officers lied. This either/or proposition is what we found most troubling in
Vargas.
We commented that “[ejven assuming that the testimony of the prosecution and defense witnesses contained unavoidable contradictions, it of course does not follow as a matter of law that in order to acquit Vargas the jury had to believe that the agents had lied.”
Vargas,
More recent cases have emphasized this distinction. In
United States v. Cornett,
2.
The defendants also claim prejudice from the Government’s characterization of Sumpter’s and Buchholz’s statements as “confessions.” Prior to his closing argument, the attorney for the Government requested that the district court allow him to argue that, pursuant to 18 U.S.C. § 3501, 8 the statements of Sumpter and Buchholz were confessions. The defendants objected, but the district court acceded in the Government’s request with the understanding that the defendants could argue that the statements did not constitute confessions. The court also gave an instruction directed to these statements. The court charged the jury:
You have received evidence of statements said to be made by defendants Sumpter and Buchholz to law enforcement officers. You must decide whether the defendants did in fact make the statements. If you find that the defen *742 dants did make the statements, then you must decide what weight, if any, you feel the statements deserve. In making this decision, you should consider all matters in evidence having to do with the statements, including those concerning the defendants themselves and the circumstances under which the statements were made.
R.91, Government’s Inst. 12.
Relying on
United States v. Morsley,
Even if'we were to agree with our colleagues on the Fourth Circuit that the prosecutor’s characterization of Buchholz’s and Sumpter’s statements constituted “tolerable trial error,” it does not follow that the defendants were deprived of a fair trial.
See Morgan,
D. Jury Misconduct
Finally, the defendants characterize Juror 99’s “curiosity” as “bias against the Defendants,” Appellants’ Br. at 48, that undermines the validity of the jury’s
*743
verdict. Because ‘“[t]he process of empaneling a jury is firmly entrusted to the sound discretion of the trial judge,”’ we shall not disturb the district court’s decision in this arena “ ‘absent an abuse of this discretion.’ ”
United States v. Beasley,
According to the juror’s own statement, she had not meant to express concern, only curiosity. Upon further questioning by the court, she stated unequivocally that she could be fair and impartial. Given these responses and the district court’s superior vantage point to evaluate the juror’s credibility in responding to its inquiries, we shall not second guess its determination that Juror 99 could faithfully execute her oath. Consequently, we shall not disturb the district court’s decision to allow the empaneled jury to sit and render judgment.
Cf. Thompson v. Altheimer & Gray,
Conclusion
For the reasons set forth above, the judgment of the district court is affirmed.
AFFIRMED
Notes
. Little had agreed to cooperate with the investigation in St. Louis at the time he entered his agreement with the Government to cooperate in this matter. See Tr. 432-36.
. Federal Rule of Evidence 402 states: "All relevant evidence is admissible, except as otherwise provided by the Constitution of the United States, by Act of Congress, by these rules, or by other rules prescribed by the Supreme Court pursuant to statutory authority. Evidence which is not relevant is not admissible.”
Federal Rule of Evidence 401 defines relevant evidence as "evidence having any tendency to make the existence of any fact that is of consequence to the determination of the action more probable or less probable than it would be without the evidence.” Fed.R.Evid. 401.
. Federal Rule of Evidence 403 states: "Although relevant, evidence may be excluded if its probative value is substantially outweighed by the danger of unfair prejudice, confusion of the issues, or misleading the jury, or by considerations of undue delay, waste of time, or needless presentation of cumulative evidence.”
. The defendants also point to
United States v. Cheska, 202
F.3d 947 (7th Cir.2000), in support of their contention that the district court abused its discretion in admitting Special Agent Scheitlin’s testimony. We cannot agree.
Cheska
did not involve the admission of evidence but instead involved prosecutorial misconduct that stemmed from a comment that a witness “had convicted 23 other people” when evidence of the witness’ prior cooperation had not been admitted into evidence.
Cheska,
. The comment to 5.11 states that "[t]he bracketed paragraph in (a) may be used as additional or substitute language in cases involving charges of conspiracy, RICO or CCE.” Furthermore, all of the cases that the defendants cite in support of their proposition that the instruction should be given are conspiracy cases. See Appellants' Br. at 31. No conspiracy was charged in the present case and, therefore, it is not clear that the omitted language is applicable to these defendants.
. Our conclusion also finds support in the commentary to Pattern Instruction 5.11. The Committee Comment to the instruction states: "As a general rule, (a) and (b) are alternative instructions. The bracketed paragraph in (a) may be used as additional or substitute language in cases involving charges of conspiracy, RICO or CCE.” The comment to the proffered instruction, therefore, belies the defendants’ suggestion that the instruction, as given, was inadequate because paragraphs (a) and (b) of 5.11 were designed to be given in the alternative, and not the conjunctive.
. Because we do not believe any prosecutorial misconduct occurred, it is unnecessary for us to engage in the second of the two-part inquiry — whether prejudice occurred as a result of the misconduct.
. 18 U.S.C. § 3501 defines “confession” to include “any self-incriminating statement made or given orally or in writing.”
Cf. Dickerson v. United States,
.
See United States v. Goodlow,
