Full opinion text
COFFEY, Circuit Judge. This is the consolidated appeal of fourteen individuals who, based on their involvement in a heroin importation and distribution conspiracy, were convicted of various offenses under the federal narcotics laws. On appeal, they raise a number of arguments challenging their convictions and/or sentences. We affirm. I. FACTUAL BACKGROUND This case arises out of an extensive heroin network centered in Chicago, Illinois. Between 1984 and 1986 this drug enterprise imported approximately three kilograms of heroin having an estimated street value of over one million dollars into the United States from Pakistan, India and Nigeria. The heroin, most of which was smuggled into this country by female couriers concealing the drug in their body cavities, was then transported to the Chicago area for distribution. In addition to the importers and couriers, this organization employed a number of distributors who were responsible for the “cutting” and packaging of the heroin, as well as street dealers, the individuals within the organization ultimately charged with keeping a steady supply of heroin in Chicago. In early 1986, confidential informants working with the Chicago Police Department (“CPD”) and the United States Drug Enforcement Administration (“DEA”) introduced undercover law enforcement officials to Folorunsho Ogundipe and Surakatu Shittu, the central figures controlling the drug network. On January 10, 1986, CPD Officer Nathaniel Reed met with Ogundipe and purchased approximately one-half ounce of heroin for $3,500. Two weeks later, on January 24, Officer Reed went to Ogundipe’s apartment to make a second purchase of heroin. Upon his arrival, Reed encountered defendant Phyliss Briscoe, whom Ogundipe introduced as his wife. Shortly thereafter, Ogundipe told Briscoe to leave the apartment and get the “package.” Briscoe returned approximately fifteen minutes later carrying a small paper bag, informed Ogundipe that she “got it,” and went into the bedroom with him. Ogundipe returned with a one-ounce package of heroin, and Reed paid him $7,000. Between January and April 1986, Officer Reed also negotiated with Ogundipe for the purchase of a kilogram of heroin. Ogun-dipe informed Reed that a purchase of this size would involve a trip to Nigeria and that he (Ogundipe) could guarantee Reed safe passage to and from Nigeria by providing Reed with falsified passports and making the necessary arrangements, i.e., bribing, various “U.S. customs officials on his payroll.” During one of their meetings, Ogundipe drove Reed to the residence of Gbolahan Taiwo, who, according to Ogun-dipe, was the individual in charge of all the Nigerian heroin in Chicago. Ogundipe entered Taiwo’s residence, returning approximately fifteen minutes later with a small package of heroin for Reed. At approximately the same time, DEA Agent Robert Smith began purchasing heroin from Shittu. Shittu informed Agent Smith that he imported heroin from Nigeria through the use of female couriers and would be traveling to Nigeria himself to obtain a kilogram of heroin. Shittu also stated that he could supply Smith with as much heroin as he needed for a price of $6,500 to $7,500 an ounce. In March 1986, Agent Smith met with both Shittu and Ogundipe in Ogundipe’s apartment and purchased one ounce of heroin for $7,500. While in Ogundipe’s apartment, Agent Smith met Phyliss Briscoe, whom Ogundipe again introduced as his wife. At the close of this meeting, Shittu informed Smith that he was leaving for Nigeria and that while he was away, Ogundipe would be able to supply Smith with heroin. Smith entered into two subsequent transactions with Shit-tu, purchasing approximately four ounces of heroin for $25,500. Based on this evidence, the DEA obtained authorization to intercept and record telephone calls to and from the residences of Shittu, Ogundipe and Taiwo, located in Chicago. The government operated a wiretap on Shittu’s telephone from September 22 to November 12, 1986. Ogundipe’s calls were monitored from September 22 until October 22. The wiretap on Taiwo’s telephone commenced on October 16 and terminated on November 12. Through this wiretap investigation, the DEA was able to monitor the conversations of Shittu, Ogun-dipe and Taiwo, as well as identify the individuals listed on telephone company records as the subscribers to the numbers making calls to or receiving calls from these residences. The majority of the intercepted conversations were conducted in Yoruba, a language spoken in Nigeria, thus necessitating that the DEA task force charged with monitoring the conversations of Shittu, Ogundipe and Taiwo include individuals who could provide English translations of the conversations occurring during the wiretap investigation. Once these conversations were translated and combined with the subscriber information from the incoming and outgoing calls, the law enforcement officials learned of Shittu’s, Ogundipe’s and Taiwo’s heroin dealings with defendants Abdul Disu, Kola Ajibade, Charles Dina, Isaac Orija, Idris Duale, Ola-dipo Erinle, Albert Davies, Alaba Zach Iji-tola, Leonard Smith, James King, Alonzo Manning, and Jacqueline Simmons, all of whom were ultimately arrested and indicted as defendants in this case. The wiretap investigation also led to the arrests of three drug couriers and their escort at O'Hare International Airport in Chicago on October 23, 1986. On October 22, Shittu received a call from an individual identifying himself as “Kunle,” who was later identified as defendant Adekunle Ade-fuye. Adefuye stated that he had been sent by “Mrs. Agbabs” and that he had just arrived in New York City from Nigeria. Adefuye asked Shittu if he could handle “one door” (one kilogram of heroin) and Shittu stated that he would take as much as Adefuye could bring with him. Adefuye made a second call to Shittu’s residence in which the two discussed the price for the heroin Adefuye was transporting to Chicago. On October 23, Adefuye called Shittu a third time, stating that he and three female couriers would be arriving in Chicago that evening on American Airlines Flight 277. Upon their arrival in Chicago, Adefuye and the three couriers, defendants Sherifat Usman, Fadeke Bello and Aderemi Adefuye, were arrested by DEA agents who had been dispatched to O’Hare following Adefuye’s third telephone conversation with Shittu. The three couriers were taken to a hospital near O’Hare where they were x-rayed. The x-rays revealed that each woman had a foreign object in her pelvic area. After DEA agents stated that they had obtained a court order authorizing the removal of the objects, Bello and Usman removed egg-shaped objects wrapped in black electrical tape from their vaginas. The agents opened these containers and discovered that Bello had been carrying 67.62 grams of heroin and Usman had been carrying 212.5 grams of the drug. After Aderemi refused to remove the object from her pelvic area, doctors surgically withdrew from her vagina a container similar in appearance to those of Usman and Bello in which 200.62 grams of heroin was discovered. After their arrest, Adefuye informed law enforcement officials that he and the three couriers had been sent to Chicago by defendant Michael Alii, an importer of heroin residing in New York City. Based on this information, DEA agents arrested Alii in his New York home on January 6, 1987. On March 11, 1987, a federal grand jury returned a second superseding 162-count indictment charging twenty-five individuals, including the fourteen appellants, with numerous violations of the federal narcotics laws. Count One charged all defendants with participating in a heroin importation and distribution conspiracy in violation of 21 U.S.C. § 846. Specifically, the defendants were charged with conspiring: (1) to possess with intent to distribute and to distribute heroin; and (2) to use interstate telephone lines to facilitate the importation, possession, and distribution of heroin. Counts Two through Seventeen charged several of the defendants with possession, possession with intent to distribute, and distribution of heroin in violation of 21 U.S.C. §§ 841(a)(1) and 844, and 18 U.S.C. § 2. In the remaining counts, various defendants were charged with using the telephone to facilitate the conspiracy, as well as to facilitate the actual importation and distribution of heroin in violation of 21 U.S.C. § 843(b). On May 13, 1987, a jury trial commenced as to fifteen of the defendants charged in the indictment, fourteen of whom are involved in this appeal. At trial, the government presented the testimony of CPD Officer Reed and DEA Agent Smith concerning their heroin transactions with defendants Ogundipe and Shittu, as well as the testimony from other law enforcement officials regarding the arrests of the various defendants. The government also elicited testimony from co-conspirators Shittu, Ade-fuye, King and Manning concerning their transactions with the other defendants in this case. Each of these individuals had pled guilty to certain charges in the indictment and testified pursuant to plea agreements in which the government agreed to drop the remaining charges against them. The bulk of the government’s evidence consisted of 230 tape-recorded conversations, most of which were in Yoruba, and their corresponding English transcripts. As foundation for the admission of the tapes and transcripts, the government presented the testimony of defendant Shittu detailing the identification of the voices on the tapes. The government also presented and the trial court qualified Michael Afolayan as an expert witness to testify as to the English translations of the Yoruba tapes. Afolay-an, a native Nigerian and an expert in the Yoruba language, had listened to the tapes of the conversations conducted in Yoruba and aided in translating the conversations into English and preparing the English transcripts which were ultimately submitted to the jury. After two months of trial, the case was submitted to the jury on July 16, 1987. On July 20, 1987, the jury returned a verdict finding all defendants guilty of conspiracy to distribute heroin in violation of 21 U.S.C. § 846. In addition to their convictions for conspiracy, all of the defendants involved in this appeal were convicted on at least one other count in the indictment. All of the appellants were sentenced on September 23, 1987, with the exception of Davies, who was sentenced on December 9, 1987. To the extent that further facts may be necessary to fully address the issues raised on appeal, such facts will be incorporated into our discussion of the merits of the appellants’ challenges to their convictions and sentences. II. JURY SELECTION The appellants, all of whom are black, initially contend that reversal of their convictions is required because the government violated their equal protection rights in using its peremptory challenges to exclude blacks from the trial jury. Specifically, the appellants argue that the government removed six black venirepersons from the jury based solely on their race and that the trial court’s finding that the government did not commit purposeful discrimination in removing these members of the venire is clearly erroneous. In Batson v. Kentucky, 476 U.S. 79, 106 S.Ct. 1712, 90 L.Ed.2d 69 (1986), the Supreme Court held that the Equal Protection Clause forbids the government from exercising peremptory challenges to remove black venirepersons from the petit jury based solely on their race or on the assumption that black jurors will be unable to consider the case against a black defendant impartially. Id. at 89, 106 S.Ct. at 1719. In so holding, the Court set forth an evidentiary framework for assessing whether the prosecution’s use of its peremptory challenges violates general principles of equal protection. Under this framework a defendant who is a member of a cognizable racial group “may make out a prima facie case of purposeful discrimination by showing that the totality of the relevant facts gives rise to an inference of discriminatory purpose.” Id. at 93-94, 106 S.Ct. at 1721. Once the defendant establishes a prima facie case, the burden shifts to the government to articulate a neutral explanation for challenging the black venirepersons. Id. at 94, 106 S.Ct. at 1722. “[T]he prosecutor’s explanation need not rise to the level justifying exercise of a challenge for cause.” Id. at 97, 106 S.Ct. at 1723. However, the government may not satisfy its burden by merely denying any discriminatory motive and asserting its good faith in individual selections. Id. at 98, 106 S.Ct. at 1724. Rather, the government’s explanation must be “clear and reasonably specific” and set forth “legitimate reasons” for the challenges, all of which must be “related to the particular case to be tried.” Id. at 98 and n. 20, 106 S.Ct. at 1724 and n. 20. If the government’s explanation satisfies these requirements, “[t]he trial court then will have the duty to determine if the defendant has established purposeful discrimination.” Id. at 98, 106 S.Ct. at 1724. In the present case the trial court allotted twelve peremptory challenges to the government. The government exercised a total of seven strikes, six of which were against blacks. Defense counsel, citing Batson, objected to five of the six strikes exercised against blacks, arguing that the government was purposefully using its per-emptories to remove blacks from the panel of prospective jurors. In response to the defendant’s objections, the government articulated its reasons for striking the black venirepersons. The trial court found that the government’s reasons were legitimate and, thus, that the defendants had failed to demonstrate a Batson violation. On appeal, the parties do not dispute that the defendants established a pri-ma facie case of racial discrimination under Batson nor do they dispute that the burden shifted to the government to articulate neutral explanations for its peremptory challenges. What is in dispute is whether the trial court erred in determining that the government did not commit purposeful discrimination based on its finding that the government’s explanations for challenging the black veniremen were not racially motivated. The appellants argue that the court’s finding is erroneous because the reasons the government articulated for striking the black veniremen were not legitimate, but rather were mere pretexts for discrimination. The appellants carry a heavy burden in challenging the findings of the trial court. As the Supreme Court recognized in Batson: “Since the trial judge’s findings in the context under consideration here largely will turn on evaluation of credibility, a reviewing court ordinarily should give those findings great deference.” Id. at 98 n. 21, 106 S.Ct. at 1724 n. 21. Thus, we may overturn the trial court’s determination that the government’s peremptory challenges were not motivated by intentional discrimination only if it is clearly erroneous. Id. Applying these standards to the facts of this case, we are convinced that the trial court properly found that the government did not use its peremptory challenges to exclude black veniremen from the petit jury based on racial considerations. The transcript of the jury selection proceedings reveals that after each of the defendants’ objections to the peremptory challenges against black venirepersons, the government set forth its rationale for striking the particular juror. The Assistant United States Attorneys representing the government explained that it challenged juror Karen Jackson, a black female, because she had previously worked as a youth supervisor at the Illinois Youth Correctional Center, a penal facility for young persons convicted of criminal violations, and feared she might have a tendency to be sympathetic toward the defendants and their reasons for engaging in criminal activity. The appellants argue that the government’s reason for striking Jackson is pretextual because the government’s assumption of bias is contradicted by Jackson’s statement that her experience as a youth supervisor would not prejudice her and that she could be fair to both sides. This argument ignores the fact that the Supreme Court in Batson “emphasize[d] that the prosecutor’s explanation need not rise to the level justifying exercise of a challenge for cause.” 476 U.S. at 97, 106 S.Ct. at 1723. Had Jackson stated that she would be biased due to her previous employment at the Illinois Youth Correctional Center, she certainly would have been dismissed for cause. We agree with the trial court that the government articulated a legitimate, race-neutral explanation for the exercise of its peremptory challenge against juror Jackson. Juror Andrew Cooper, a black male, stated during the court’s voir dire examination that he had been accused of assault and battery, but had been acquitted of the charge because the judge in his trial found the evidence to be “too circumstantial.” The government explained that due to Cooper's acquittal based on circumstantial evidence, “he would empathize with the defendants unnaturally and possibly not consider the circumstantial evidence we present.” Given the significance of circumstantial evidence in a conspiracy case such as this, see United States v. Vega, 860 F.2d 779, 793-94 (7th Cir.1988), we are of the opinion that the government’s reservations concerning juror Cooper were well founded and, in any case, were not motivated by racial concerns. Thus, we uphold the trial court's determination that the government’s peremptory challenge against Cooper on this basis was proper. Juror Donald Jeffries, a black male, testified on voir dire that he was an unemployed student and that during the last five years he had resided at three different addresses on the west side of Chicago. The Assistant United States Attorneys stated that all three of these addresses were “geographically close” to the addresses of two individuals, Fanny Chambers and Joseph Henley, who were scheduled to testify that they had engaged in heroin transactions with defendant Shittu, and that, in their opinion, the government’s interest would be disserved by allowing “a juror who somehow may be personally familiar with, if not the people involved, certainly the area involved where these events have taken place.” The appellants argue that the possibility that juror Jeffries was acquainted with the two government witnesses is too remote to justify Jeffries’ removal from the venire. We disagree. At trial, Shittu testified that between 1984 and 1986 he distributed a significant amount of heroin to Fannie Chambers, a heroin dealer operating on the west side of Chicago. Given the widespread activities of the heroin distribution network in this case, coupled with the fact that Chambers conducted her own distribution operation in close proximity to the area where Mr. Jeffries resided, it is quite likely that Jeffries might very well have been familiar with, if not Chambers herself, the individuals involved as purchasers and/or distributors within Chambers’ operation, thus justifying the government’s peremptory challenge. Other courts have upheld peremptory challenges based on similar concerns. See United States v. Mitchell, 877 F.2d 294, 303 (4th Cir.1989); United States v. Davis, 871 F.2d 71, 73-74 (8th Cir.1989); United States v. Tindle, 860 F.2d 125, 129 (4th Cir.1988). We are cognizant of the fact that the west side of Chicago is predominantly black and that exclusion of jurors based solely on their residence in this area of the city could be a pretext for discrimination. However, the government’s explanation for its strike went well beyond a cursory statement that Mr. Jeffries resided on the west side of Chicago. The government explicitly stated that Jeffries’ last three separate addresses where he had resided in the immediate past were geographically close to the addresses of Chambers and Henley. Defense counsel, both at trial and on appeal, failed to present any evidence that Jeffries’ residences were not in close proximity to the area where these individuals conducted their illicit activities. In light of these circumstances, as well as our deference to the trial court’s opportunity to assess the credibility of the prosecutors, we affirm the trial court’s determination that the government’s reasons for challenging Mr. Jeffries were legitimate. Juror Grant Owens, a black male, testified that he had been unjustly convicted of aggravated assault because the Cook County (Illinois) State’s Attorney’s Office persuaded him to plead guilty despite his representations of innocence. Owens stated that due to this conviction he had been denied employment with the federal government on two separate occasions. As with juror Jackson above, the defendants merely refer to Owens’ statement that he could be a fair and impartial juror. In light of his past experience with the criminal justice system, this attempt to attack the government’s reasons for challenging Mr. Owens borders on the frivolous. We affirm the trial court’s finding that the government’s peremptory challenge against Mr. Owens was properly exercised. Juror Jerry Beal, a black male, testified that he had been the victim of a crime involving armed violence and that no court proceeding occurred regarding this incident. The Assistant United States Attorneys stated that they “detected in [Beal] some resentment over the fact that there was nobody charged in [the] crime and that this ‘resentment’ would inure to the detriment of the government.” The appellants argue that the prosecutors’ perception of resentment in Mr. Beal is a subjective determination based only on their own intuition and, thus, is insufficient to justify the peremptory challenge. This argument was rejected in United States v. Lance, 853 F.2d 1177, 1181 (5th Cir.1988), where the Fifth Circuit stated: “[T]he vagarious process of choosing jurors need not be controlled by a simple equation; it may be influenced by intuitive assumptions that are not fairly quantifiable ... and by the interplay of various factors.” Accord United States v. Terrazas-Carrasco, 861 F.2d 93, 94 (5th Cir.1989) (“Valid reasons for exclusion may include ‘intuitive assumptions’ upon confronting a venireman.”). See also Davis, supra, 871 F.2d at 73. The government articulated a facially valid explanation for excluding Beal. Giving due deference to the trial court’s opportunity to observe the credibility of the prosecutors, we refuse to disturb the court’s finding that the government articulated legitimate reasons under Batson for striking Beal. In sum, we agree with the trial court that in light of the government’s race-neutral explanations for peremptorily challenging the black venirepersons discussed above, the defendants failed to establish purposeful discrimination in the jury selection process. In addition to the facial validity of the government’s explanations, we note that the jury ultimately empaneled consisted of six blacks, one Oriental, and five whites. Moreover, all four of the alternate jurors were black. Although “the striking of a single black juror for racial reasons violates the equal protection clause, even though other black jurors are seated,” United States v. Battle, 836 F.2d 1084, 1086 (8th Cir.1987), the fact that ten black jurors were seated when the government left five of its twelve allotted peremptory challenges unused strongly supports the trial court’s finding that the government did not act with discriminatory intent during jury selection. On this record, we are convinced that the court’s finding is not clearly erroneous. Accordingly, we hold that the appellants’ jury was selected in accordance with the Batson mandate. III. EVIDENTIARY RULINGS The appellants raise numerous arguments challenging the evidentiary rulings made by the district court during the course of the trial. We note that the appellants carry a heavy burden in challenging the trial court’s evidentiary rulings on appeal because “ ‘a reviewing court gives special deference to the evidentiary rulings of the trial court.’” United States v. Shukitis, 877 F.2d 1322, 1327 (7th Cir.1989) (citation omitted). Thus, we will reverse such rulings only upon a showing that the trial court committed an abuse of discretion. United States v. Alvarez, 860 F.2d 801, 807 (7th Cir.1988). With this standard in mind we address the appellants’ arguments seri-atim. A. Transcripts of Tape-Recorded Telephone Conversations Defendants Disu, Ajibade and Davies contend that the trial court erred in allowing the jury to use government-prepared transcripts containing English translations of tape-recorded telephone conversations in which they and the other defendants spoke almost exclusively in Yoruba. Specifically, the defendants contend that the government failed to establish that the transcripts were authentic versions of the recorded conversations because the methods used to translate the conversations and identify the parties thereto were inherently untrustworthy. We consider the defendants’ argument in view of the well-established rule that “[cjourts possess wide discretion in determining whether to permit the jury to use written transcripts as aids in listening to tape recordings.” United States v. Keck, 773 F.2d 759, 766 (7th Cir.1985). Accord United States v. Carrasco, 887 F.2d 794, 804-07 (7th Cir.1989); Vega, supra, 860 F.2d at 791; United States v. Zambrana, 841 F.2d 1320, 1335 (7th Cir.1988). With regard to the method used to identify the voices on the various tapes, DEA Agent Michael Streicher testified that after the conversations were recorded, he and Surukatu Shittu listened to the tapes, Shittu identified the participants in the conversations, and Streicher took notes as to Shittu’s identifications which were later transferred to the transcripts. According to the defendants, this procedure was inherently untrustworthy because the government failed to establish Shittu’s familiarity with their voices and failed to identify the individuals who affixed the names of the speakers to the transcripts. We disagree. As an initial matter, we are of the opinion that the government clearly established Shittu’s familiarity with the voices of the defendants alleged to be the speakers on the tape recordings. We recently set forth the standard of familiarity necessary for an authenticating witness to identify the voices of participants in conversations recorded on tape: “Federal Rule of Evidence 901(b)(5) ... permits voice identification ... to be made ‘by opinion based upon hearing the voice at any time under circumstances connecting it with the alleged speaker.’ As long as the basic requirement of familiarity is met, lay opinion testimony is an acceptable means for establishing the speaker’s identity.” Vega, 860 F.2d at 788. Shittu’s identification of the defendants’ voices comports with this standard. Shittu testified that he had spoken with all of the defendants prior to identifying the voices on the tapes. With respect to the particular defendants challenging the voice identification procedure on appeal, Shittu testified that he had spoken with Disu and Ajibade on at least 150 occasions. Although Shittu was not as familiar with Davies, he testified that he had known Davies for five years and that they had been involved in at least three heroin transactions together. Shittu also stated that he had spoken with Davies while they were incarcerated prior to trial. Thus, there is little question that the government established that Shittu was sufficiently familiar with the voices of Disu, Ajibade and Davies to identify their voices on tape. The defendants also argue that the government failed to identify the individuals who affixed the names of the defendants onto the transcripts, thus precluding them from inquiring into the method used to identify the speakers. We recently rejected a similar challenge to the voice identifications on government-prepared transcripts in Alvarez, supra. In that case we dismissed the defendants’ attack on the transcripts, also based on the government’s failure to identify the individuals affixing speakers’ names to the transcripts, in light of the testimony of voice identification witnesses who had substantial familiarity with the defendants implicated in the recorded conversations, as well as the extensive opportunity afforded defense counsel to cross-examine the witnesses concerning their identification of the defendants’ voices. Alvarez, 860 F.2d at 812. As noted above, the government clearly established Shittu’s familiarity with the voices of Disu, Ajibade and Davies. More importantly, defense counsel extensively cross-examined Shittu concerning statements allegedly made by the defendants in particular transcripts. Thus, there was sufficient evidence elicited for the jury to assess the reliability of the government’s method for assigning speakers’ names to the various statements in the transcripts and determine the proper weight to be given to the various voice identifications. The defendants also argue that the English transcripts of the tape-recorded Yoruba conversations were inaccurate because Michael Afolayan, the government’s language expert, did not prepare the transcripts “from scratch.” Rather, Afolayan, while listening to the tapes, reviewed and corrected preliminary versions of the transcripts prepared by the Nigerians deputized as United States Marshals (“Nigerian deputies”) who worked with DEA agents during the wiretap investigation. According to the defendants, Afolayan’s method of preparing the final versions of the transcripts renders them inaccurate because of “a person’s propensity to hear what they [sic] see written.” At the outset, we note that the defendants failed to offer an alternate version of the transcript containing their own translations of the Yoruba conversations, nor did they present an expert witness to testify that Afolayan’s translations were, in fact, inaccurate. In Zambrana, supra, we adopted the following procedure for resolving challenges to the accuracy of transcripts: “ ‘Initially, the district court and the parties should make an effort to produce an “official” or “stipulated” transcript, one which satisfies all sides. If such an “official” transcript cannot be produced, then each side should produce its own version of the disputed portions. In addition, each side may put on evidence supporting the accuracy of its version or challenging the accuracy of the other side’s version. This procedure is well suited to cases such as that before us, where the transcript is an English translation of a foreign language conversation. Such a procedure does not tie a defendant to an “official” transcript prepared by the prosecution, nor does it “usurp” the fact-finder’s function. If there is a dispute as to the contents of a foreign language recording the burden will lie with the respective parties to present transcripts or other evidence to support their version of the conversation.’ ” 841 F.2d at 1335-36 (quoting United States v. Llinas, 603 F.2d 506 (5th Cir.1979)). Moreover, in Zambrana we agreed with the Llinas court’s “[holding] that 1 “[o]nce we have concluded that the defendants could have challenged specific portions of the government’s transcript or prepared an alternate version, it follows that they cannot be heard to complain on appeal because they failed to take advantage of their trial opportunity.” ’ 603 F.2d at 509 (quoting United States v. Wilson, 578 F.2d 67, 70 (5th Cir.1978)).” Zambrana, 841 F.2d at 1335. In this case, because the defendants failed to present their own translation of the Yoruba conversations and also failed to present an expert witness to demonstrate possible inaccuracies in the translated transcripts, despite the trial court’s explicit statement that defense counsel could do so, they have certainly limited their opportunity to challenge the accuracy of the government’s transcripts on appeal. It is undisputed that Afolayan was an expert in the Yoruba language. Moreover, the defendants were given the opportunity to, and did in fact, cross-examine Afolayan regarding his translations. It is clear that the jury, like the trial court, was convinced that the government’s translations in the transcripts were reliable and accurate, That the defendants were unable to cast doubt on the translations is due in large part to their own failure to present alternate translations or an expert witness of their own to discredit the testimony of the government’s translator. Thus, we hold that the transcripts were properly provided to the jury as an aid while listening to the tape-recorded conversations. On a related note, although the defendants extensively cross-examined Afolayan regarding his translations of the tape-recorded Yoruba conversations, they nonetheless argue on appeal that the trial court unduly restricted their opportunity to cross-examine Afolayan effectively in violation of the Confrontation Clause of the sixth amendment. Specifically, the defendants contend that their confrontation rights were violated by the trial court’s ruling precluding them from questioning Afolayan about differences between the Nigerian deputies’ preliminary drafts and the final drafts submitted to the jury which Afolayan had prepared, as well as the notes Afolayan made on the preliminary drafts regarding the translations contained therein. The trial court precluded the defendants from questioning Afolayan on the preliminary documents, ruling that Afolayan had not prepared the preliminary drafts and, thus, could not testify as to why the Nigerian deputies’ translations differed from the translations Afolayan had prepared. The court went on to state that the preliminary transcripts constituted hearsay because, in effect, they were the statements of out-of-court declarants. With regard to Afolayan’s notes, the court ruled that defense counsel could impeach Afolay-an with the notes, provided counsel could establish that the notes were inconsistent with Afolayan’s final translations. The main thrust of the defendants’ argument that the trial court’s ruling violated their confrontation rights is that without learning of the discrepancies between the preliminary and final versions of the transcripts, the jury could not possibly have reached an informed decision regarding the weight to be given the final transcripts. The sixth amendment’s Confrontation Clause provides: “In all criminal prosecutions, the accused shall enjoy the right ... to be confronted with the witnesses against him.” Included within this right is the guarantee that a defendant will have an effective opportunity to test the accuracy of adverse evidence. Ohio v. Roberts, 448 U.S. 56, 65, 100 S.Ct. 2531, 2538-39, 65 L.Ed.2d 597 (1980). However, this guarantee does not include the opportunity to test the evidence “in whatever way, and to whatever extent the defense might wish.” Delaware v. Fensterer, 474 U.S. 15, 20, 106 S.Ct. 292, 295, 88 L.Ed.2d 15 (1985) (per curiam). In the present case, the defendants sought to question Afolayan concerning documents which he had not prepared —namely, the preliminary transcripts prepared by the Nigerian deputies. As noted above, Afolayan, while listening to the tape-recorded conversations, reviewed, corrected and edited the translations contained in these documents. Although Afolayan was competent to testify as to his own translations, we agree with the trial court that he was not competent to testify as to the reasons why the Nigerian deputies translated the Yoruba conversations in the manner in which they did. Indeed, Afolayan was not present when the deputies listened to the Yoruba conversations, nor did he participate in the preparation of the preliminary transcripts. In any case, the fact that there may have been some discrepancies between Afolayan’s translations and those of the Nigerian deputies does not somehow give the defendants the right to engage in unfettered cross-examination of Afolayan. “[A]s we observed in United States v. Zambrana, 841 F.2d [at] 1337 ...: ‘In our view a foreign language translation is sufficiently accurate to assist the jury if the “translation” reasonably conveys the intent or idea of the thought spoken. It is axiomatic that a translation of most foreign languages to English (and vice versa) can never convey precisely and exactly the same idea and intent comprised in the original text, and it is unrealistic to impose an impossible requirement of exactness before allowing a translation to be considered by a jury.’ Differences in grammar between languages, for example, could preclude exact translation of sentences. Accordingly, we are most reluctant to disturb a district court’s admission of a translated transcript without some clear demonstration of inaccuracy.” Carrasco, supra, 887 F.2d at 806 n. 19. The defendants extensively cross-examined Afolayan regarding his translations — the only version submitted to the jury — as well as his expertise in Yoruba and the intricacies of the language itself. As noted above, the trial court informed defense counsel that if he wished to challenge Afo-layan’s translations, he was free to present an expert witness to testify that Afolayan’s translations of the tape-recorded conversations were inaccurate. However, the defendants failed to present such expert witness. We agree with the previous holding of this court in which this court has been hesitant to find Confrontation Clause violations in situations where defendants have failed to take full advantage of the opportunity for cross-examination afforded them by the trial court. See United States v. Mayomi, 873 F.2d 1049, 1057 n. 9 (7th Cir.1989). Under these circumstances we refuse to hold that the trial court violated the defendants’ confrontation rights. Cf. Alvarez, 860 F.2d at 812. In sum, the jury was presented with extensive testimony, including thorough direct and cross-examination regarding the procedures used to identify the voices on the tapes, as well as the methods employed to translate the Yoruba conversations into English. We are of the opinion that this extensive examination of the witnesses provided the jury with sufficient information to determine the accuracy of the voice identifications and translations, as well as the method used to attribute certain statements to the defendants. Thus, we hold that the defendant’s challenge to the district court’s decision to allow the jury to use the government’s transcripts as an aid to listening to the taped conversations is without merit. B. Telephone Records Defendants Orija, Erinle, Duale and Smith challenge the admission of computerized telephone records under Fed.R. Evid. 803(6). The telephone records listed the telephone numbers, the names of the subscribers placing calls to, as well as the subscribers receiving calls from, the three telephone numbers that were the subjects of the DEA wiretap investigation, the date, time and length of the call. The defendants allege that the trial court abused its discretion in admitting the telephone records because the government failed to present sufficient foundational evidence to establish that the computer records were accurate compilations of the telephone call data associated with the three “wiretapped” telephones. It is well established that computer data compilations are admissible as business records under Fed.R.Evid. 803(6) if a proper foundation as to the reliability of the records is established. United States v. Croft, 750 F.2d 1354 (7th Cir.1984). A proper foundation is established if the government demonstrates that the business records, in this case, the computerized telephone records, “are kept in the course of regularly conducted business activity, and [that it] was the regular practice of that business activity to make records, as shown by the testimony of the custodian or other qualified witness.” United States v. Chappell, 698 F.2d 308, 311 (7th Cir.), cert. denied, 461 U.S. 931, 103 S.Ct. 2095, 77 L.Ed.2d 304 (1983). “Business records are reliable to the extent they are compiled consistently and conscientiously.” United States v. Ramsey, 785 F.2d 184, 192 (7th Cir.1986). At trial, the government presented the testimony of Merny Miller, the keeper of the records at Illinois Bell Telephone Company. Miller testified that the telephone records proffered by the government were Automatic Message Accounting Interrogation sheets which are compilations of call data entered into a computer when an Illinois Bell subscriber places a telephone call prepared for billing purposes. According to Miller, it was the regular business practice of Illinois Bell to assemble and maintain the records of the subscriber’s telephone calls. Moreover, Miller also stated that the computer assembling the call data scanned itself for error every fifteen seconds. Finally, defense counsel were given an opportunity to, and did in fact, cross-examine Miller on all of the information concerning the telephone records presented at trial. In light of these facts, we are convinced that the government’s foundation evidence established the reliability of Illinois Bell’s computerized telephone records. Despite the government’s extensive foundation evidence, as well as the defendants’ opportunity to cross-examine Miller, the defendants argue that the foundation for the computer records is deficient because the government failed to establish that the computers were tested for internal programming errors on a monthly basis as were the computers in United States v. Weatherspoon, 581 F.2d 595, 598 (7th Cir.1978). Although the government did, in fact, present such evidence in Weather-spoon, that case in no way requires that such a showing be made in every case as a prerequisite to the admission of computer records. As long as the government provides sufficient facts to warrant a finding that the records are trustworthy and the opposing party is afforded an opportunity to inquire into the accuracy thereof and how the records were maintained and produced, a proper foundation has been established. See Croft, 750 F.2d at 1365 n. 7. From our review of the testimony, we are convinced that the government’s foundation in this case complies with this standard and hold that the trial court’s admission of the telephone records was not an abuse of discretion. C. Transcript Cover Sheets Defendants Orija, Erinle, Duale and Smith argue that the district court erred in allowing the government to submit cover sheets with the transcripts of the tape-recorded telephone conversations. Each cover sheet listed the following information: (1) the date and time of the telephone call; (2) the identified parties to the conversation; and (3) the subscribers of the telephone numbers making and receiving the call. The court admitted the cover sheets as summaries under Fed.R.Evid. 1006, which provides: “The contents of voluminous writings, recordings, or photographs which cannot conveniently be examined in court may be presented in the form of a chart, summary, or calculation.” Specifically, the court ruled that because the jury would be considering 238 tapes and their corresponding transcripts, the cover sheets would be an aid to the jury in understanding the telephone record exhibits and testimony and would provide them with an efficient method for identifying the tapes and transcripts, most of which corresponded to specific counts in the indictment charging telephone facilitation in violation of 21 U.S.C. § 843(b). See infra section IV.B. The defendants argue that the court improperly admitted the cover sheets because the summaries did not accurately represent the evidence upon which they were based and because the tapes and transcripts were not too voluminous to present in their original form. “The admission of a summary under Fed. R.Evid. 1006 requires ‘a proper foundation as to the admissibility of the material that is summarized and ... [a showing] that the summary is accurate;’ however, the decision to admit or exclude the summary rests in the district court’s sound discretion.” United States v. Driver, 798 F.2d 248, 253 (7th Cir.1986) (quoting Needham v. White Laboratories, Inc., 639 F.2d 394, 403 (7th Cir.), cert. denied 454 U.S. 927, 102 S.Ct. 427, 70 L.Ed.2d 237 (1981)). Our review of the court transcript reveals that the information contained in the cover sheets was corroborated by: evidence from the government’s wiretap investigation (dates and times of the calls); Shittu’s voice identification testimony (parties to the conversations); and Illinois Bell telephone records (subscriber information). Thus, we reject the defendants’ contention that the information on the cover sheets did not accurately reflect the evidence presented at trial. We also reject the defendants’ argument that the trial court erred in admitting the cover sheets because the tapes and transcripts were not too voluminous to present in their original form. The defendants are not aided by the fact that the tapes and transcripts were, in fact, presented in their original form. Rule 1006 “does not require that it be literally impossible to examine all the underlying records, but only that in-court examination would be an inconvenience.” United States v. Possick, 849 F.2d 332, 339 (8th Cir.1988). In view of the numerous tapes and transcripts presented in this ease, as well as the importance of separating this evidence as it pertained to each defendant, we hold that the district court’s admission of the transcript cover sheets as an aid to the jury in interpreting the voluminous records and documents presented by the government was not an abuse of discretion. D. Shittu’s Explanation of Narcotics Terms Defendants Disu, Ajibade and Davies argue that the trial court erred in allowing defendant Shittu to testify as to the meaning of certain words allegedly referring to narcotics used in the tape-recorded conversations in which he was not a participant. The district court ruled that Shittu was competent to testify as to the meaning of these terms under Fed.R.Evid. 602 based on the fact that he had personally dealt with many of the defendants alleged to be the speakers on tape. Furthermore, the court ruled that under Fed.R.Evid. 702 and 703, Shittu could testify as an expert witness based on his experience in the field of narcotics trafficking. The defendants’ attack on Shittu’s testimony focuses almost solely on the Rule 602 aspect of the trial court’s ruling. Essentially they argue that it was never established that Shittu and the other defendants formulated specific code words to signify terms relating to the distribution of narcotics. In our opinion the defendants interpret the trial court’s ruling too narrowly. Whether or not Shittu and the other defendants formally established a narcotics code is irrelevant. The fact of the matter is that such code language was used. As we stated in Vega, supra: “The fact that tapes of the conversations implicating Vega in the drug conspiracy may, in certain parts, have been somewhat unclear, does not preclude a determination that he participated in the conspiracy. As we observed in United States v. Zanin, 831 F.2d 740, 744 (7th Cir.1987): ‘Conversations regarding drug transactions are rarely clear. A fact-finder must always draw inferences from veiled allusions and code words.’ In this case the jury was confronted with conversations which contained ‘code words’ that, when considered in isolation, might seem unclear, veiled and almost nonsensical, but when analyzed properly, in the context of the totality of the evidence, can be clearly seen to be ‘code words’ for drugs. See generally United States v. Abascal, 564 F.2d 821, 827 (2nd Cir.1977) (‘The conversing conspirators frequently discuss non-narcotic-related matters at the beginning of conversations, and often resorted to jargon and code words, a frequent practice in narcotics dealings’); United States v. Chavez, 533 F.2d 491, 494 (9th Cir.1976) (‘Jargon and code words are commonly used by those dealing in illicit drugs and were employed here’) (citation omitted). It is true that, advisedly, no explicit mention was ever made of cocaine or other drugs in any of Vega’s conversations with the Zambra-nas. However, a case was made, which was more than strong enough to convince the jury, the trier of fact, that Vega used terms like ‘chickens,’ ‘roosters’ and ‘it’ as code words for drugs. Not only are code words always used by drug conspirators when they realize, as they do in today’s drug culture, that their telephone conversations are frequently intercepted, such terms were obviously used by the conspirators in this case. Tom Lovely, a convicted member of the ... conspiracy, testified clearly and without qualification that he had been instructed to use code words for drugs when speaking on the telephone.” 860 F.2d at 795. It is most apparent that members of a narcotics organization are uniquely qualified to testify as to the code words used by their fellow conspirators. In this case, the record is replete with references to where the speakers on tape used such isolated terms as “tar” and “show” to mean heroin; “red” and “white” to signify the color of heroin; and “one” and “two” to signify the quantity of heroin being discussed. Thus, we reject the defendants’ argument that the trial court improperly allowed Shittu to testify under Rule 602. In any case, even if we agreed with the defendant’s arguments under Rule 602, which we do not, we agree with the trial court’s ruling that given Shittu’s extensive knowledge and experience as a narcotics dealer, as well as his many dealings with the other defendants, Shittu was well qualified to offer his interpretation of the meaning of the code terms and phrases used in the tape-recorded conversations as an expert witness under Rules 702 and 703. These rules permit the admission of the opinion testimony of a witness qualified by the court as an expert if the “witness’ specialized knowledge will assist the trier of fact to understand the evidence in the case.” United States v. Rollins, 862 F.2d 1282, 1292 (7th Cir.1988). It is well-settled that the meaning of narcotics code words are an appropriate subject for expert testimony. Id.; United States v. Ramirez, 796 F.2d 212, 216 (7th Cir.1986). See also Vega, 860 F.2d at 782-83. Thus, we hold that the district court did not abuse its discretion in permitting Shittu to express his opinion on the meaning of code words and phrases used during the course of the telephone conversations recorded on tape. E. Ajibade’s Document Theft Defendants Dina, Ogundipe and Ijitola argue that the district court erred in admitting evidence of defendant Ajibade’s attempt to remove an airline ticket to Puerto Rico issued in the name of Joseph Shobo and charged to Ajibade’s credit card from the courtroom. During its case-in-chief, the government elicited testimony from Shittu that Ajibade was selling heroin in Puerto Rico and introduced an airline ticket to Puerto Rico issued in Ajibade’s name, which was issued for the same flights and dates of travel as the ticket issued to Shobo. After Shittu’s testimony, Ajibade and his attorney requested and received permission from the court to examine documents relating to Shittu’s testimony concerning Ajibade’s drug activities in Puerto Rico, including Shobo’s airline ticket. During Ajibade’s examination of the documents, United States Marshal Charles Wagner observed him remove the ticket from the evidence table and shove it into his sock. Wagner reported Ajibade’s actions to his superior, Julian Styne, who searched Ajibade and found Shobo’s ticket hidden in one of his socks. After learning of this series of events, the government sought on two occasions to introduce evidence of Ajibade’s attempt to remove the ticket from the courtroom, arguing that it was evidence of Ajibade’s consciousness of guilt. The court initially refused to allow the government to present this evidence, ruling that the probative value with respect to consciousness of guilt was substantially outweighed by the risk of unfair prejudice and that the jury might have difficulty considering the evidence only with respect to Ajibade and not the other defendants. During Ajibade’s presentation of evidence, Ajibade’s wife testified that she and her husband, accompanied by Shobo and his wife, traveled to Puerto Rico, but that their trip was unrelated to heroin trafficking. Following Mrs. Ajibade’s testimony, the government again sought leave to introduce evidence of defendant Ajibade’s attempt to remove Shobo’s ticket from the courtroom. Over the objection of all defendants, the trial court reversed its prior ruling and admitted this evidence, concluding that Mrs. Ajibade’s testimony had “opened the door” for the government to present evidence of Ajibade’s consciousness of guilt concerning the trip to Puerto Rico. Prior to admitting this evidence the trial court instructed the jury that the government’s rebuttal evidence applied only to Kola Ajibade and only for the limited purpose of demonstrating his consciousness of guilt. The defendants contend that this evidence was “outrageously prejudicial” to them, especially in light of the fact that this was the last evidence the jury heard before closing arguments, and thus, was inadmissible under Fed.R.Evid. 403, which provides, in relevant part: “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....” It is well established that “a trial judge’s assessment of relative probative value and unfair prejudice is generally accorded great deference because of his firsthand exposure to the evidence and his familiarity with the course of the trial proceeding.” United States v. Liefer, 778 F.2d 1236, 1244 (7th Cir.1985) (citation omitted). Accord United States v. Garner, 837 F.2d 1404, 1416 (7th Cir.1987). In asserting that the evidence of Ajibade’s document theft was inadmissible under Rule 403, the defendants place significant reliance on the trial court’s initial determination that the unfair prejudicial effect of this evidence substantially outweighed its probative value. This reliance is misplaced because the probative value of this evidence dramatically increased after Mrs. Ajibade’s testimony that the trip to Puerto Rico was not drug related. Assuming this were true, defendant Ajibade had no reason to fear the introduction of Shobo’s ticket, and thus, had no reason to surreptitiously attempt to remove the ticket from the courtroom. Thus, in light of Mrs. Ajibade’s testimony, we agree with the trial court’s decision to allow the reception of the document theft evidence for the sole and limited purpose of establishing Ajibade’s consciousness of guilt concerning his trip to Puerto Rico with Shobo. The defendants argue that even if Ajibade’s document theft is admissible under Rule 403, they were denied a fair trial because of the “spillover” prejudice inuring to them from the admission of this evidence. The defendants correctly point out that in joint trials the court must consider, and remain particularly sensitive to the possibility that the prejudicial effect of evidence admissible only as to only one or a few defendants may have a “spillover” effect on the jury’s consideration of the government’s case against defendants to whom the evidence does not apply. United States v. Davis, 838 F.2d 909, 916 (7th Cir.1988). “Generally, a cautionary instruction will be sufficient to cure any unfair prejudice ...; however, if the evidence creates an unacceptably high inference of wrongdoing against another defendant, the district court should either exclude the evidence or sever the trials.” Id. The defendants argue that the trial court’s cautionary instruction was insufficient to mitigate the unfair prejudice they suffered from the admission of Ajibade’s document theft. This argument is based entirely on the defendants’ speculative assertion that at the point in the trial when this evidence was introduced, “the jury had become conditioned to the fact — rightly or wrongly— that what one defendant said or did was attributable to each and every defendant on trial.” We refuse the defendants’ invitation to engage in such speculation. Despite the fact that the circumstances surrounding Ajibade’s document theft were presented to the jury immediately before closing argument, the evidence involved only Ajibade and his consciousness of guilt regarding activities — namely, drug trafficking in Puerto Rico — in which no defendant on trial other than Ajibade participated. In light of the trial court’s clear and repeated instructions that the jury could consider this evidence only against Ajibade on the issue of consciousness of guilt, we refuse to hold that the district court’s admission of this evidence was an abuse of discretion. F. “Other Acts” Evidence Against Alii Defendant Alii challenges the district court’s admission of the testimony of defendant Adekunle Adefuye, who stated that in addition to the trip involving the heroin couriers arrested at O’Hare, Alii had arranged four other trips during 1986 in which couriers working for and on behalf of Alii smuggled heroin from foreign countries, including Nigeria, to New York in their body cavities. Alii also challenges the admission of the testimony of Internal Revenue Service Agent Patrick McDer-mott, who stated that Alii had substantial income during the years 1985 and 1986, but failed to file income tax returns for these years. Alii argues that the testimony of these witnesses was inadmissible because it involved acts not charged in the indictment falling outside the parameters of Fed.R. Evid. 404(b). That rule, which governs the admission of “other acts” evidence, provides: “Evidence of other crimes, wrongs, or acts is not admissible to prove the character of a person in order to show action in conformity therewith. It may, however, be admissible for other purposes, such as proof of motive, opportunity, intent, preparation, plan, knowledge, identity, or absence of mistake or accident.” In this circuit, district courts, before admitting “other acts” evidence under Rule 404(b), must analyze the evidence within the framework of a four-part test and determine that: “(1) the evidence is directed toward establishing a matter in issue other than the defendant’s propensity to commit the crime charged, (2) the evidence shows that the other act is similar enough and close enough in time to be relevant to the matter in issue, (3) the evidence is sufficient to support a jury finding that the defendant committed the similar act, and (4) the probative value of the evidence is not substantially outweighed by the danger of unfair prejudice.” United States v. Zapata, 871 F.2d 616, 620 (7th Cir.1989). We note that a trial court’s decision to admit “other acts” evidence is reversible only upon a showing that the court committed a clear abuse of discretion. Id. at 621. With this standard in mind, we address Alli’s arguments concerning his prior heroin trafficking activities and his failure to file income tax returns in 1985 and 1986. 1. Prior Heroin Trafficking Activities At trial, Adefuye testified that between January and August of 1986, Alii organized a number of trips in which female couriers transported heroin in their body cavities from foreign lands, including Nigeria, to Alli’s home in New York. Ade-fuye also testified that defendant Aderemi had been a courier on two of these trips and that the defendants Usman and Bello acted as couriers on one of these trips. The government offered and the trial court admitted Adefuye’s testimony as evidence of Alli’s intent, knowledge and preparation regarding the October 1986 trip in which Adefuye, Aderemi, Usm