Full opinion text
REENA RAGGI, Circuit Judge: Defendant Henk Rommy appeals from a judgment of conviction entered on January 27, 2006, in the United States District Court for the Southern District of New York (Jed S. Rakoff, Judge), following a jury trial at which he was found guilty on one count of conspiracy to import methy-lenedioxymethamphetamine, commonly known as “MDMA” or “ecstasy,” into the United States in violation of 21 U.S.C. §§ 952(a), 963. Presently incarcerated serving a twenty-year sentence, Rommy challenges his conviction on the grounds that the district court erred (1) in charging the jury that venue in the Southern District of New York could be established by a telephone call placed by an undercover agent in that district to Rommy in the Netherlands; and (2) in admitting evidence obtained in violation of the mutual legal assistance treaty in effect between the United States and the Netherlands, as well as various provisions of the Constitution and the Federal Rules of Evidence. Because we conclude that the alleged errors are either without merit or, in any event, harmless, we affirm the judgment of conviction. I. Factual Background From at least 1980, Dutch national Henk Rommy, also known as the “Cobra,” headed an international drug ring that trafficked in large quantities of controlled substances. The trial evidence establishing Rommy’s guilt included the testimony of co-conspirators, recorded conversations between Rommy and both a government informant and an undercover agent of the Drug Enforcement Administration (“DEA”), and statements volunteered by Rommy to federal agents with whom he asked to speak while incarcerated in Spain pending extradition to the United States. A. Co-conspirator Testimony 1. Background Evidence as to Rom-my’s European Drug Trafficking Thomas Bosch, a Swiss banker turned drug trafficker, testified that, in the late 1980s and continuing for more than a decade thereafter, he and confederate Jack Zuchetto smuggled hundreds of kilograms of hashish from Rommy in the Netherlands to buyers in Switzerland. In or about 2000, Bosch learned from Zuchetto that Rommy was experiencing problems smuggling ecstasy pills into Switzerland and that he sought their assistance in transporting a 100,000-pill shipment from the Netherlands to Zurich. Bosch testified that the pills in question were light blue in color and stamped with the logo of the late Italian fashion designer Gianni Versace. After successfully completing this delivery, Bosch helped smuggle two more shipments of ecstasy pills into Switzerland for Rommy. 2. Rommy Recruits Bosch to Smuggle Ecstasy into the United States In 2000, Rommy also asked Bosch to smuggle one million ecstasy pills into the United States. Bosch explained that he had acquired some familiarity with transporting drugs into this country because, in the three preceding years, he and his fian-cée, Daniela Rinaldi, had smuggled approximately 120 kilograms of hashish and marijuana into the United States, concealing the drugs in recreational vehicles shipped from Europe. Rommy told Bosch that he wanted the ecstasy imported into New York. When Bosch expressed a preference for Miami as the port of entry, Rommy agreed, advising Bosch that his New York contacts could travel to Miami to pick up the shipment. Eventually, Bosch and Rommy decided that half the pill shipment would be given to Rommy’s New York confederates while Bosch would transport the remainder into Mexico for sale in that country. Bosch would convert the proceeds from the ecstasy shipment into cocaine for delivery to Rommy in Europe. In return, Rommy would pay Bosch one dollar per pill successfully smuggled, for an anticipated total of $1 million. When, in late 2000, it came time to execute the million-pill shipment, Bosch could not locate Rommy. In fact, Rommy had been arrested by Dutch authorities in connection with an unrelated investigation into his drug activities. He remained incarcerated from November 2000 until May 2001. 3. Rommy’s Involvement in the Allen/Bosch/Rinaldi Shipment In 2000, Bosch and Rinaldi successfully smuggled a load of ecstasy into the United States for a different Dutch trafficker named Redouan. Redouan arranged for the drugs to be sold in Miami by Thomas Allen. Upon the successful completion of this scheme, Bosch, Rinaldi, and Allen decided to team up to import another ecstasy shipment totaling 800,000 pills into the United States in 2001. As Bosch and Ri-naldi each testified, Allen agreed to procure the pills in the Netherlands and to be financially responsible for half the shipment; Bosch and Rinaldi agreed to transport the pills into the United States and to be financially responsible for the remaining half. After the 800,000 ecstasy pills were successfully smuggled into Miami, Allen told Rinaldi that Allen’s half of the shipment had to be sold first because it belonged to the “Cobra” (ie., Rommy), who wanted his money right away. In fact, Allen did sell his half of the shipment; meanwhile Bosch and Rinaldi were arrested by Florida authorities in possession of the remaining 400,000 pills. B. The DEA Undercover Investigation 1. Dutch Authorities Alert DEA Agents to Rommy’s Interest in Smuggling Ecstasy into the United States In early 2000, at the same time that Rommy was plotting with Bosch, Rinaldi, and Allen to smuggle ecstasy pills into the United States, Dutch authorities contacted DEA agents stationed in the Netherlands to advise them that a confidential informant, Alexander Van der Laan DeVries (“DeVries”), had been approached by Rommy to transport ecstasy to New York City. After debriefing DeVries, the DEA decided to use him to introduce Rommy to an undercover agent, Mark Grey, whose purported criminal connections at New York ports would allow him to smuggle ecstasy into New York cached in vintage cars. 2. The Treaty Requests for Dutch Assistance To facilitate this plan, in April 2000, pursuant to a mutual legal assistance treaty then in effect between the United States and the Netherlands, see Treaty on Mutual Assistance in Criminal Matters, June 12, 1981, U.S.-Neth., 35 U.S.T. 1361, T.I.A.S. No. 10,734 (“MLAT”), the United States formally requested Dutch authorization to employ various investigative techniques in the Netherlands. Specifically, the United States sought to use DeVries in an undercover capacity and, pursuant thereto, to make audio or video recordings in the Netherlands of conversations between the confidential informant and Rommy. Authorization was also requested for United States officials to wiretap Rommy’s telephone in the Netherlands. Dutch authorities denied the April 2000 request. A second MLAT request from the United States, in September 2002, sought access to evidence and witnesses developed by Dutch authorities in the course of their investigations into Rommy’s criminal activities. In granting this request, the Netherlands provided the United States with a transcript of an October 30, 2000 telephone call intercepted by the Dutch police in which Rommy and an unnamed confederate discussed the limited supplies of “Ver-sace t-shirts.” At trial, the government would use Bosch’s testimony about ecstasy pills stamped with the Versace logo to argue that this conversation related to drugs. See infra at 137-38. 3. The Recorded Telephone Calls Despite the denial of the initial MLAT request, United States authorities proceeded with their plan to use DeVries in an undercover investigation of Rommy, but they conducted no electronic monitoring in the Netherlands. Instead, between October 2001 and March 2003, DEA agents working in Manhattan recorded five telephone calls in which Rommy, DeVries, and Agent Grey engaged in thinly veiled discussions about smuggling ecstasy into New York. Because the location of the parties and the initiator of the calls are issues relevant to the venue argument on appeal, we duly note these facts. It is undisputed that the first recorded call was placed by DeVries in Manhattan to Rommy in the Netherlands on October 20, 2001. In that conversation, DeVries not only told Rommy that he was in New York City, he specifically reported that he was standing near the site of the recently destroyed World Trade Center. With respect to the smuggling plan, Rommy asked DeVries if his “friend” (Agent Grey) was going “to look at the car.” Telephone Tr. Oct. 20, 2001, at 1. When DeVries replied that this had already been done, Rommy inquired, “Do you think he can sell it, do you think?” Id. DeVries assured Rommy of his friend’s ability to do what was necessary, and advised that he (DeVries) would be back in the Netherlands the following week. It would be almost a year before the next recorded call on September 17, 2002. On that date, DeVries was again in Manhattan meeting with federal agents at the United States Attorney’s Office. According to the agent who recorded this call, Rommy, who was then in the Netherlands, placed the call to the informant’s cell phone. At trial, Rommy’s counsel disputed his client’s initiation of the call, an argument made possible by the fact that the recording of the start of the call was inaudible., In the ensuing conversation, DeVries reported that he was “going to come to Spain with Mark [ie., Agent Grey].” Telephone Tr. Sept. 17, 2002, at 2. Rommy stated that he would meet the men there. The Spain meeting, scheduled for October 4, 2002, never took place because, from October 2-4, Rommy was once again detained by Dutch authorities conducting an unrelated investigation. A third recorded telephone call occurred on October 17, 2002. Agent Grey testified that, on that date, while in his Manhattan office, he received an unexpected call on an undercover telephone from Rommy and DeVries who were then together in the Netherlands. Because it took Grey a few moments to attach a recording device to the telephone, the initial part of the conversation was not recorded. Grey testified, however, that the first voice he heard on the line was Rommy’s, who introduced himself as “Alex’s friend” and who apologized for missing the meeting in Spain. Trial Tr. 61. The defense challenged this account, arguing that DeVries placed the call because his was the first voice recorded speaking with Grey. The government disputed this contention, noting that, within moments, Grey asked DeVries to “put him \i.e., Rommy] back on.” Telephone Tr. Oct. 17, 2002, at 2 (emphasis added). In the course of this conversation, Rommy stated that he was “famous in Holland,” to which Grey replied that he was not interested in fame, just in “do[ing] some business together.” Id. at 3. Rommy told Grey, “[D]on’t worry. I see you soon.” Id. It was undisputed that the fourth and fifth recorded calls were placed by Agent Grey in Manhattan to Rommy in the Netherlands. In the fourth call, on February 25, 2003, for which DeVries was present with Rommy, the three men planned a meeting. In agreeing to the proposed schedule, Rommy stated, “Ok, no problem. I can do a lot of things.” Telephone Tr. Feb. 25, 2003, at 3. In the final recorded telephone conversation on March 14, 2003, Rommy was initially distracted, explaining, “I have a lot of problems. Somebody must pay me some money, about, ah, $240,000.” Telephone Tr. Mar. 14, 2003, at 2. Soon thereafter, however, Rommy confirmed that he would meet with Grey the following week. 4. The Videotaped Meeting in Bermuda On March 23, 2003, Rommy met with Agent Grey and DeVries at a hotel in Bermuda to finalize a deal to import 300,-000 ecstasy pills into New York City. In a videotaped meeting lasting more than an hour, Rommy provided the most compelling evidence of his own guilt. Speaking openly of his experience in narcotics trafficking generally and ecstasy trafficking in particular, Rommy explained that ecstasy pills were made from special oils produced in China. According to Rommy, two liters of the oil could yield 8,000 ecstasy pills for a total cost of $2,500; those 8,000 pills, in turn, could command $150,000 on the open market. Rommy stated that he had “friends” who could get 2,000-3,000 liters of the oil per year, Videotape Tr. Mar. 23, 2003, at 48, and he bragged of his connections with Dutch drug laboratories that “make the best stuff,” id. at 50. Agent Grey represented to Rommy that his contacts at the ports in New York would allow him to get drug-laden cars through customs without inspection. Grey nevertheless told Rommy that, once he got the ecstasy pills into the United States, he did not want to be responsible for their disposal. Rommy assured Grey that he already had people in New York City ready to accept the ecstasy shipment, and that these individuals would pay Grey in “cash right away” upon delivery. Id. at 37. When Grey indicated a preference to be paid in pills, Rommy agreed to give Grey one-third of the shipment — 100,000 out of a total of 300,000 pills — as a transportation fee. C. Rommy’s Prison Interview in Spain Following the Bermuda meeting, United States authorities made an international request for Rommy’s provisional arrest. On November 12, 2003, Spanish authorities, acting on this request, took Rommy into custody and detained him in a Madrid prison. While extradition proceedings were pending, Rommy, through his girlfriend Laura de Vreeze, requested a meeting with DEA representatives in Spain. At the time, Rommy had been represented for more than eight months in the extradition proceedings by two Spanish attorneys. In response, DEA Special Agent John Fernandez, accompanied by a DEA intelligence analyst, an inspector from the Spanish police, and Ms. de Vreeze, met with Rommy in the Madrid prison on August 26, 2004. At no time during this meeting was Rommy advised that he had rights pursuant to Miranda v. Arizona, 384 U.S. 436, 86 S.Ct. 1602, 16 L.Ed.2d 694 (1966), or asked for an explicit waiver of those rights. Instead, after introducing himself, Agent Fernandez asked Rommy why he had requested a meeting. Rommy replied that he was facing extradition to the United States where he knew that penalties for drug trafficking were more severe than in Europe. He had sought a meeting to proffer his cooperation to the DEA “in setting up other traffickers that he knew, in exchange for leniency at sentencing.” Trial Tr. 556. Agent Fernandez told Rommy that he could not promise any leniency because Rommy’s immediate fate lay in the hands of Spanish authorities and, even if he were extradited to the United States for prosecution, leniency “was ultimately the decision of a judge.” Id. Agent Fernandez then offered to end the meeting, but Rommy stated that he still wished to go forward and provide information. Rommy proceeded to speak at some length and in detail about areas of potential cooperation. He described himself as a well-known international drug broker whose nickname was the “Cobra.” To confirm his notoriety, Rommy showed Agent Fernandez press clippings from Dutch newspapers that included his photo and reported on his criminal exploits. Rommy emphasized his ability to target very high-level traffickers and proceeded to disclose names and background information on more than a dozen such persons, including Bosch, Zuchetto, Allen, and DeVries. Rommy expressed confusion as to his own arrest, insisting that he had never sent ecstasy to the United States despite being pushed to do so by others, notably, DeV-ries. Rommy stated that DeVries had recently arranged a meeting in Bermuda where Rommy had spoken with a smuggler who could clear drugs into New York’s ports. Unfamiliar with any of the persons or facts disclosed by Rommy — not even with the fact that the “smuggler” whom Rommy met in Bermuda was an undercover DEA agent — Fernandez simply took notes as Rommy spoke, interrupting the defendant only to ask follow-up questions that sought the spelling of names, the dates when recounted events occurred, and, on one occasion, a clarification as to a substance that Rommy referred to as “BMK,” apparently an ingredient of ecstasy. Several weeks later, Agent Fernandez and Rommy’s lawyers discussed a possible second meeting. Fernandez reported that Rommy’s lawyers were enthusiastic about such a meeting and expressed disappointment when it did not materialize. D. Rommy’s United States Prosecution 1. Indictment Rommy was originally indicted by a grand jury in the Southern District of New York in July 2002, well before his provisional arrest in Spain. That initial indictment charged Rommy with one count of conspiracy to import ecstasy into the United States in violation of 21 U.S.C. §§ 952(a), 963. Two superseding indictments were filed in November and December 2003, expanding the time frame of the charged conspiracy and adding a forfeiture allegation. 2. Suppression Motions After extradition to the United States and before trial, Rommy moved to suppress various evidence, including (1) the recorded telephone calls and the videotape of the Bermuda meeting, which he challenged as the fruits of an unlawful DEA undercover operation conducted in violation of the MLAT; and (2) the statements he made to the DEA while incarcerated in Spain pending extradition, which he claimed were procured in violation of the Fifth and Sixth Amendments. The district court denied these motions as without merit. 3. The Challenged Venue Charge Rommy’s trial commenced on September 20, 2005. The government introduced the extensive incriminating evidence already detailed. As was his right, Rommy offered no evidence. He did, however, move for a judgment of acquittal pursuant to Rule 29 of the Federal Rules of Criminal Procedure based on the government’s alleged failure to establish venue in the Southern District of New York. The district court denied the motion but pursued the venue question further with counsel at the charging conference. Specifically, the district court rejected defendant’s request to instruct the jury that venue in the Southern District of New York had to be proved beyond a reasonable doubt, charging instead that the government could carry its venue burden by a preponderance of the evidence. The district court further proposed to charge the jury — by way of example — that a telephone call made in furtherance of the conspiracy by a defendant outside the Southern District to a non-conspirator within the district could establish venue in the district. While acknowledging the existence of some cases indicating that even calls “going the other way,” ie., from a non-conspirator in the district to a defendant outside the district, might suffice, Trial Tr. 632, the court reserved judgment on that possibility: “I think I want to think a little bit more about this issue of the [outgoing] phone call,” id. at 634. In the end, the issue was left unresolved, and the court charged the jury as follows with respect to venue: Finally, you must determine whether any action in furtherance of the alleged conspiracy occurred at least in part in the Southern District of New York. This is called “venue,” and, unlike all the other requirements, which must be proven beyond a reasonable doubt, the government is only required to prove venue by a preponderance of the evidence; that is, that it is more probable than not. [Court defines Southern District] It is not necessary that the government prove that all or even most of the conspiracy was carried out in the Southern District of New York. Rather, it is sufficient if you find by a preponderance of the evidence that any act in furtherance of the conspiracy occurred at least in part in the Southern District of New York. For example, if you find by a preponderance of the evidence that after the alleged conspiracy was formed, a telephone call in furtherance of the conspiracy was made to a location in the [district], that would be sufficient to fulfill the venue requirement, even if the call was made to an undercover agent or some other nonconspirator. Id. at 748-49. In the course of its deliberations, however, the jury itself raised the outgoing call issue, asking, “[C]an venue be proved by an outgoing call; in other words, if [Special [Ajgent Grey made a call out to Henk Rommy on October 17, does that constitute venue[?]” Id. at 773. Disclosing the inquiry to counsel, the district court observed, “So the issue that we have ducked has come back and can no longer be ducked.” Id. Rommy’s counsel demurred, insisting that the outgoing call issue had already been decided in Rommy’s favor, that counsel had relied on that decision in summation, and that any response allowing the jury to base venue on an outgoing call would violate Federal Rule of Criminal Procedure 30(b), which requires the trial court to inform parties before summations of its rulings on requested instructions. The district court disagreed. It observed that it had given the jury “an example” of an incoming call supporting venue, but this was “not a definitive ruling excluding all other possibilities.” Id. at 774. It concluded that venue could be established by an outgoing call from Agent Grey within the district to Rommy outside the district “if [the call] meets the other requirements for an act in furtherance of a conspiracy.” Id. at 778. The court rejected defense counsel’s argument that Rommy would “have to know that Agent Grey was in New York at the time” of the outgoing call for such a call to establish venue. Id. The court also denied Rommy’s request to charge the jury further on the issue of manufactured venue, finding that the issue was “totally before [the jury],” and that the requested instruction was not responsive to the jury’s particular inquiry. Id. at 780. Following this colloquy, the district court responded to the jury’s venue inquiry as follows: The first question is, can venue be proved by an outgoing call. The answer to that is yes, a call that originates in the Southern District of New York can go somewhere else if it meets the other requirements to support venue just like an incoming call. In the instructions I used an example of an incoming call, but an outgoing call that meets the requirements would also support venue in the Southern District of New York. The second question is, “In other words, if [S]pecial [A]gent Grey made a call out to Henk Rommy (10/17) does that constitute venue.” The answer to that is it could. Remember, you have to find before you can find that any such call in either direction supports venue that, first, there was already a conspiracy formed and, second, that the call in some manner furthered the conspiracy. Now, a third party can initiate a call, it doesn’t have to be a co-conspirator, obviously, [S]peeial [A]gent Grey was not a co-conspirator; on the other hand, a call that is initiated by someone who is not a co-conspirator would not count unless it was a call that in some fashion was either induced by the ongoing conspiracy or in some way furthered the ongoing conspiracy. Id. at 782-83. On September 30, 2005, the jury returned a guilty verdict. 4. Sentencing At sentencing, the district court found that Rommy had conspired to import at least 1.7 million ecstasy pills into the United States. This quantity included the aborted one-million pill agreement with Bosch and Rinaldi; the 400,000 pills that Rommy gave Thomas Allen as part of the 800,000-pill Allen/Boseh/Rinaldi shipment in 2001; and the 300,000 pills discussed with Grey and DeVries in Bermuda. With an offense level of 40 and a criminal history of V, Rommy’s Sentencing Guidelines range provided for a prison term of 360 months to life. This range was, however, limited by the statutory maximum term of twenty years’ incarceration. See 21 U.S.C. §§ 960(b)(3), 963. Rejecting defense arguments for leniency, the district court sentenced Rommy to the maximum twenty-year prison term, observing that he was “a hardened, sophisticated, career criminal” who had organized “international drug deals whose scope and sophistication is outweighed only by their intrinsic value.” Sentencing Tr. Jan. 17, 2006, at 21. In addition to twenty years’ incarceration, the court sentenced Rommy to three years’ supervised release, a $100 special assessment, and a forfeiture judgment in the amount of $1 million. Rommy timely appealed the judgment of conviction. II. Discussion A. Challenge to Venue Instructions Rommy asserts that the district court’s jury instructions as to venue were flawed in two respects: (1) in identifying the government’s venue burden as a preponderance of the evidence rather than proof beyond a reasonable doubt, and (2) in allowing the jury to find venue in the Southern District of New York based on calls made by an undercover agent in Manhattan to defendant in the Netherlands. We review legal challenges to jury instructions de novo, and, even where we identify error, we will reverse a conviction “only if the charge, taken as a whole, was prejudicial.” United States v. Gaines, 457 F.3d 238, 244 (2d Cir.2006) (quoting United States v. Caban, 173 F.3d 89, 94 (2d Cir.1999)); see United States v. Ford, 435 F.3d 204, 209-10 (2d Cir.2006); see also United States v. Ramirez, 420 F.3d 134, 139 (2d Cir.2005) (noting that questions of law pertaining to venue are reviewed de novo). In this case, we conclude that neither of defendant’s challenges to the venue charge has merit. 1. The Preponderance Burden Rommy’s argument that venue must be proved beyond a reasonable doubt requires little discussion. The government’s burden to establish venue originates in two provisions of the Constitution. Article III, section 2, states, in relevant part, that criminal trials “shall be held in the State where the said Crimes shall have been committed.” U.S. Const. art. III, § 2, cl. 3. The Sixth Amendment further guarantees that a criminal defendant “shall enjoy the right to a speedy and public trial, by an impartial jury of the State and district wherein the crime shall have been committed.” Id. amend. VI. In furtherance of these provisions, Rule 18 of the Federal Rules of Criminal Procedure requires that, “[ujnless a statute or these rules permit otherwise, the government must prosecute an offense in a district where the offense was committed.” Fed.R.Crim.P. 18. As this court has frequently observed, the venue requirement, despite its constitutional pedigree, “is not an element of a crime” so as to require proof beyond a reasonable doubt; rather, venue need be proved only “by a preponderance of the evidence.” United States v. Ramirez, 420 F.3d at 139 (emphasis added); United States v. Chen, 378 F.3d 151, 159 (2d Cir.2004); United States v. Svoboda, 347 F.3d 471, 485 (2d Cir.2003); United States v. Bala, 236 F.3d 87, 95 (2d Cir.2000); United States v. Smith, 198 F.3d 377, 382 (2d Cir.1999). To the extent Rommy persists in arguing that venue is an element, his argument is convincingly refuted by the fact that the law treats objections to venue as waived “unless ‘specifically articulated’ in defense counsel’s motion for acquittal.” United States v. Potamitis, 739 F.2d 784, 791 (2d Cir.1984) (quoting United States v. Grammatikos, 633 F.2d 1013, 1022 (2d Cir.1980)); accord United States v. Bala, 236 F.3d at 95. Accordingly, we reject Rommy’s burden challenge to the district court’s venue instruction as meritless. 2. Basing Venue on the Site of a Government Actor’s Outgoing Call to a Conspirator Whatever burden applies to venue, Rommy submits that the district court’s response to the jury’s venue inquiry was flawed in three respects: (a) the court erred as a matter of law in instructing that telephone calls from a government actor in Manhattan to Rommy in the Netherlands could establish venue in the Southern District of New York; and, even if such calls could support venue, the instruction (b) ran afoul of Fed.R.Crim.P. 30(b) because it contradicted representations made to counsel at the charging conference; and (c) should have included a charge on “manufactured venue.” We are not persuaded. a. Telephone Calls in Furtherance of a Conspiracy Can Establish Venue Either Where Placed or Received (1) The Venue for Conspiracy The venue requirement serves to shield a federal defendant from “the unfairness and hardship” of prosecution “in a remote place.” United States v. Cores, 356 U.S. 405, 407, 78 S.Ct. 875, 2 L.Ed.2d 873 (1958). As the constitutional text makes plain, however, unfairness is generally not a concern when a defendant is tried in a district “wherein the crime shall have been committed.” U.S. Const. amend. VI. The site of a crime’s commission is not always readily determined. The commission of some crimes can span several districts. In such circumstances, Congress has instructed that venue properly lies in “any district in which such offense was begun, continued, or completed.” 18 U.S.C. § 3237(a); see United States v. Ramirez, 420 F.3d at 139. Applying this rule to the continuing crime of conspiracy, this court has held that venue may lie in any district in which the conspiracy was formed or in any district in which a conspirator committed an overt act in furtherance of the criminal scheme. See United States v. Geibel, 369 F.3d 682, 696 (2d Cir.2004); United States v. Smith, 198 F.3d at 382; United States v. Ramirez-Amaya, 812 F.2d 813, 816 (2d Cir.1987). Thus, a defendant need not himself have ever been physically present in a district for a conspiracy charge against him to be venued there. See United States v. Naranjo, 14 F.3d 145, 147 (2d Cir.1994) (holding with respect to venue that conspiracy defendant “need not have been present in the district as long as an overt act in furtherance of the conspiracy occurred there”). (2) Telephone Calls as Overt Acts (a) Calls Between Conspirators It is beyond question that telephone calls can constitute overt acts in furtherance of a conspiracy. See United States v. Smith, 198 F.3d at 382; United States v. Naranjo, 14 F.3d at 147; United States v. Friedman, 998 F.2d 53, 57 (2d Cir.1993). In cases involving telephone calls between co-conspirators in different districts, we have ruled that venue lies “in either district as long as the calls further the conspiracy.” United States v. Smith, 198 F.3d at 382. In such circumstances, the direction of the call is irrelevant to venue. Id. (noting that in United States v. Friedman, 998 F.2d at 57, where defendant in Long Island placed calls in furtherance of conspiracy to confederate in Manhattan, venue was established in the Southern District of New York, and concluding “[t]here is no reason why the opposite calling pattern should not also establish venue”); accord United States v. Kim, 246 F.3d 186, 193 n. 5 (2d Cir.2001) (observing that phone call “to or from” a district can establish venue in that district as to any member of conspiracy). Rommy submits that the reasoning in these cases cannot support venue in a district from which a non-conspirator initiates a call to a conspirator outside the district. To the extent the conspirator uses such a telephone call to further the conspiracy, we disagree. (b) Calls Between Conspirators and Norir-Conspirators (i) Calls Placed by Conspirators When one of the participants in a telephone call is a non-conspirator, such as a government actor, we have already ruled that a call in furtherance of the conspiracy placed by a conspirator outside the district to a government actor within the district is sufficient to establish venue in the district with regard to any member of the conspiracy “at least in the absence of unfairness or hardship ... arising from trial in that district, or artificial creation of venue in that district by the Government.” United States v. Naranjo, 14 F.3d at 146 (holding that telephone call from conspirator in Eastern District of New York to undercover agent in Southern District of New York established venue in Southern District as to defendant who was member of conspiracy); see also United States v. Stewart, 878 F.2d 256, 258 (8th Cir.1989) (upholding venue in North Dakota when Colorado defendant placed call to telephone in North Dakota that was programmed to forward calls to undercover agent in Minnesota). In light of this precedent, Rommy’s own telephone calls from the Netherlands to government actors in Manhattan certainly support venue in the Southern District of New York. (ii) Calls Placed by Government Actors a) The Conspirator’s Use of Such a Call to Further the Conspiracy Renders It an OveH Act On this appeal, however, we must consider whether the district court erred in allowing the jury to base its venue finding on a different scenario: telephone calls from government actors within the district to Rommy in the Netherlands. Although this court has not previously considered whether such circumstances can establish venue in the district where the call was initiated, two of our sister circuits have answered that question in the affirmative. In United States v. Cordero, 668 F.2d 32 (1st Cir.1981), the First Circuit considered whether telephone calls from an undercover agent in the District of Puerto Rico to conspirators outside that district could establish venue in Puerto Rico to prosecute a conspiracy to import drugs into the island. In an opinion by then-judge Breyer, the First Circuit ruled that such outgoing calls supported venue in Puerto Rico: Sorren and Cordero [the co-conspirators] spoke to Jimenez [the undercover agent] while he was in Puerto Rico and provided him with key information, which was then communicated to others. The fact that Jimenez placed the calls to Cordero and to Sorren who were outside the Commonwealth, does not change the fact that Cordero and Sorren transmitted this information through Jimenez who was inside Puerto Rico. Moreover, they knew he was in Puerto Rico and they knew the offense was bound for completion in Puerto Rico. It is not as if Jimenez were a traveler making chance use of a telephone at a bus stop. Thus, we think it highly likely that the offense was “continued” in Puerto Rico. Id. at 44 (citations omitted). In Andrews v. United States, 817 F.2d 1277 (7th Cir.1987), an Illinois defendant was prosecuted in the Western District of Wisconsin for unlawfully using a telephone to facilitate cocaine distribution in violation of 21 U.S.C. § 843(b). The trial evidence showed that, while in Illinois, the defendant had received at least one telephone call from an undercover agent in the Western District of Wisconsin who indicated interest in buying cocaine. The Seventh Circuit upheld venue in Wisconsin, observing that “section 843(b) proscribes a continuing offense and, as a result, the crime is committed both where the call originates and where it is received.” Id. at 1279. The Seventh Circuit noted that “it appears clear from the record that [defendant] knew that at least one phone call was from [Wisconsin],” but it reserved decision on “whether venue would be proper in Wisconsin without the defendant’s knowledge that the call originated from there.” Id. at 1280 n. 2. In response to defendant’s complaint that, “allowing venue to be determined by the origin of the call, when the defendant does not make the call, could lead to forum-shopping on the part of the government,” id. at 1279, the Seventh Circuit observed that there was no evidence of forum-shopping in the case before it. “To the extent that [forum-shopping] is a concern in a given case, it is more appropriately handled at the trial level by a transfer to a more reasonable forum, pursuant to Fed.R.Crim.P. 21.” Id. at 1279-80. We agree with the First and Seventh Circuits that a telephone call placed by a government actor within a district to a conspirator outside the district can establish venue within the district provided the conspirator uses the call to further the conspiracy. Indeed, we conclude that the critical factor in conspiracy venue analysis is not whether it is a conspirator or a government actor who initiates the call; nor does it matter whether the conspirator is communicating with someone who is a knowing confederate, an undercover agent, or an unwitting third-party. What is determinative of venue — as the district court emphasized to the jury — is whether the conspirator used the telephone call to further the objectives of the conspiracy. See United States v. Naranjo, 14 F.3d at 147 (‘We see no basis for imposing any more rigorous requirement concerning the content of the phone calls than that they do further the conspiracy.”). When a conspirator uses a telephone call — by whomever initiated — to further a criminal scheme, the conspirator effectively propels not only his voice but the scheme itself beyond his own physical location into that of the person with whom he is speaking. See United States v. Johnson, 323 U.S. 273, 275, 65 S.Ct. 249, 89 L.Ed. 236 (1944) (holding that venue may constitutionally lie in any area through which “force propelled by an offender operates”). In short, the conspirator avails himself of modern technology to commit at long distance the identical overt act that he would commit by being in the same room with a person and whispering a conspiracy-furthering message directly into his listener’s ear. In the latter circumstance, the conspirator’s commission of an overt act does not depend on whether the listener rather than the conspirator initiates the conversation. Nor does it matter whether the listener is a confederate, an innocent third party, or an undercover agent. What matters is that the conspirator speaks, not to hear the sound of his own voice, but to communicate to his listener because he thinks that, by doing so, he furthers a conspiratorial goal. Thus, the overt act may properly be understood to have occurred at the site where the listener receives the conspirator’s message. That an instrument of commerce or technology permits the conspirator to communicate with his listener while physically removed from him does not alter the fact that the conspirator has committed an overt act at the recipient’s location. It means simply that his communication is a continuing act, supporting venue in the district of its initiation as well as the district of its receipt. As the Supreme Court recognized more than sixty years ago with respect to use of the mails, venue may constitutionally lie “in the district where [a defendant] sent the goods, or in the district of their arrival, or in any intervening district.” Id. Accordingly, even with respect to telephone calls placed by non-conspirators to conspirators, we adhere to our precedent that the direction of the call is irrelevant to venue. Calls “to or from” a district can constitute overt acts sufficient to establish venue, provided that the conspirator uses the call to further the objectives of the conspiracy. United States v. Kim, 246 F.3d at 193 n. 5 (emphasis added); see also United States v. Smith, 198 F.3d at 382; United States v. Naranjo, 14 F.3d at 147; United States v. Friedman, 998 F.2d at 57. b) The Foreseeability of Venue Rommy submits that, even if a call initiated by a government actor to a conspirator can support venue in the calling district, the district court erred in refusing to instruct the jury that the defendant had to know his caller’s location. See United States v. Reed, 773 F.2d 477, 481 (2d Cir.1985) (discussing fairness of venue in the “sense of having been freely chosen by [the defendant] as the place at which the [overt] acts were committed”); see also United States v. Ramirez, 420 F.3d at 143 (observing that “inquiry should not end with finding that venue properly lay” pursuant to statute; court should determine whether location of venue is constitutional). Rommy notes that such knowledge was present in both Andrews and Cordero. See Andrews v. United States, 817 F.2d at 1280 n. 2 (noting fact without deciding whether it was essential to venue); United States v. Cordero, 668 F.2d at 44. Preliminarily, we observe that the law does not require a defendant to have actual knowledge that an overt act will occur in a particular district to support venue at that location. At most, it asks that the overt act’s occurrence in the district of venue have been reasonably foreseeable to a conspirator. See United States v. Rowe, 414 F.3d 271, 279 (2d Cir.2005) (holding that, in prosecution for electronically advertising to distribute child pornography in violation of 18 U.S.C. § 2251(d), even though defendant posted advertisement from home in Kentucky, venue was proper in Southern District of New York because defendant “must have known or contemplated that the advertisement would be transmitted by computer to anyone the whole world over who logged onto the site” (internal quotation marks omitted)); United States v. Svoboda, 347 F.3d at 483 (collecting cases with respect to foreseeability of venue). In this case, although the district court did not specifically instruct the jury as to the foreseeability of venue in the Southern District of New York, the evidence supporting that conclusion is so compelling that, if there was an error in that omission, it was plainly harmless. See generally Neder v. United States, 527 U.S. 1, 10-16, 119 S.Ct. 1827, 144 L.Ed.2d 35 (1999); California v. Roy, 519 U.S. 2, 5, 117 S.Ct. 337, 136 L.Ed.2d 266 (1996). The first recorded telephone call of the investigation, placed by DeVries to Rommy on October 20, 2001, establishes Rommy’s knowledge that he was being called from the Southern District of New York. In reporting to Rommy that he had successfully made contact with someone who could help them smuggle drugs, DeVries stated, “I am with my friend [ie., Agent Grey] in New York.” Telephone Tr. Oct. 20, 2001, at 2. Indeed, DeVries effectively told Rommy that he was in Manhattan by noting that, as they spoke, he was looking at the site of the recently collapsed World Trade Center. From this conversation, Rommy would have to have foreseen the reasonable likelihood that future telephone calls from the smuggler contact (Agent Grey) would emanate from his base of operations in New York. See generally United States v. Svoboda, 347 F.3d at 483 (holding that defendant, who was “savvy investor,” could reasonably foresee that his stock trades would be executed on either NYSE or AMEX in Southern District of New York); United States v. Kim, 246 F.3d at 193 (holding that defendant who knew his victim paid invoices from a bank located in the Southern District of New York could reasonably foresee mailings in that district). Thus, if the district court had instructed the jury on Rommy’s ability to foresee the location of the government agent’s calls, we have no doubt that the jury would still have found venue. Indeed, this conclusion is only reinforced by evidence that it was Rommy’s specific conspiratorial purpose to smuggle ecstasy pills into New York. Rommy acknowledged both to his confederates Bosch and Rinaldi and to Agent Grey that fellow conspirators were already in New York ready to accept delivery of the smuggled pills and to pay for their transport. It was in this context that Rommy encouraged DeVries to find someone to facilitate the pill shipment through New York’s ports. Once DeVries told Rommy that he had located such a “friend in New York,” Telephone Tr. Oct. 20, 2001, at 2, Rommy “must have known or contemplated” that subsequent telephone calls from this smuggler would likely emanate from New York, United States v. Rowe, 414 F.3d at 279 (internal quotation marks omitted). Like Cordero, then, this is not a case in which venue in the Southern District of New York is the product of some “chance use of a telephone” by a government agent. United States v. Cordero, 668 F.2d at 44. Rather, the calls here at issue were placed from or to the Southern District of New York because Rommy himself had identified New York as the desired destination point of his smuggling scheme and was aware that individuals who could further the scheme were located in New York. See id. (citing defendants’ knowledge that undercover agent was in District of Puerto Rico and that drug smuggling scheme “was bound for completion in Puerto Rico” in concluding that call from agent to defendants “continued” crime in that district). Accordingly, we conclude that the district court correctly charged the jury that a call placed by a government actor in Manhattan to Rommy in Amsterdam could establish venue in the Southern District of New York provided Rommy used the call to further the objectives of the charged conspiracy. b. The Challenged Charge Did Not Violate Fed.R.Crim.P. 30 Rommy contends that the challenged jury charge nevertheless violated Rule 30 of the Federal Rules of Criminal Procedure because it was at odds with agreements reached at the charging conference about how the jury would be instructed as to venue. We disagree. Rule 30 both permits parties to “request in writing” specific jury instructions, see Fed.R.Crim.P. 30(a), and requires the trial court to rule on those requests “before closing arguments,” id. 30(b). The rule is grounded in “basic concepts of fairness,” allowing “counsel to conform their arguments to the law as it will thereafter be presented by the judge to the jury.” United States v. James, 239 F.3d 120, 124 (2d Cir.2000) (internal quotation marks omitted). The rule can thus be violated by a trial judge “giving instructions that he did not inform counsel he would give, or by not giving instructions that he informed counsel he would.” Id. Reversal on the basis of a Rule 30 violation is warranted, however, only “where the defendant can show that he was substantially misled in formulating his [closing] arguments or otherwise prejudiced.” Id. (internal quotation marks omitted); accord United States v. Prawl, 168 F.3d 622, 629 (2d Cir.1999); United States v. Adeniji, 31 F.3d 58, 64 (2d Cir.1994). That is not this case. The question whether venue could be based on a call from a government actor in the Southern District of New York to Rommy in the Netherlands was first raised in connection with defendant’s Rule 29 motion for acquittal. The district court concluded, “I don’t have to reach that [question]” because there is evidence of “a call initiated by the defendant” to the Southern District of New York. Trial Tr. 613. When the issue resurfaced at the charging conference, the record shows that the district court made no ruling: “I think I want to think a little bit more about this issue of the [outgoing] phone call.” Id. at 634. Ultimately, it opted to finesse the point, offering the jury an illustrative example of venue that did not address the possibility of outgoing calls establishing venue: For example, if you find by a preponderance of the evidence that after the alleged conspiracy was formed, a telephone call in furtherance of the conspiracy was made to a location in the Southern District of New York, that would be sufficient to fulfill the venue requirement, even if the call was made to an undercover agent or some other noncon-spirator. Id. at 748-49 (emphasis added). Neither the prosecution nor the defense requested the district court to decide the outgoing call issue before summation. Rather, the parties, no less than the district court, apparently took a chance that the jury might decide the case without any need to resolve the outgoing-call question. The gamble did not pay off. The jury’s direct inquiry about outgoing calls, posed in the midst of deliberations, required the district court to address the question left unanswered at the charging conference: whether the outgoing-call evidence could support venue. In these circumstances, we identify no Rule 30 violation. As our case law makes plain, when a defendant is on notice that the propriety of a particular jury instruction is subject to further consideration by the court, he cannot claim to have been substantially misled in framing his summation. See United States v. Eisen, 974 F.2d 246, 256-57 (2d Cir.1992) (holding that where defendant “was on notice that his requested charge was the subject of further consideration,” he “could not have been substantially misled by the Court in formulating his summation argument” (internal quotation marks omitted)). Indeed, although Rommy contends that the challenged instruction was prejudicial because it “cut the legs out from beneath” his manufactured venue argument, Appellant’s Br. 35, the instruction did no such thing. Assuming the viability of a manufactured venue defense — which is debatable, see infra at 126-28 —that doctrine functions only as a basis for rejecting venue in cases in which the factual predicates for venue are established. Cf. United States v. Myers, 692 F.2d 823, 847 n. 21 (2d Cir.1982) (challenging venue, despite overt acts in Eastern District of New York, based on purported government overreaching in steering those acts into district). By instructing the jury that outgoing calls from, as well as incoming calls to, a government agent in the Southern District of New York could constitute factual predicates for venue in that district, the district court in no way undermined Rommy’s argument that, whatever predicates might support venue in the Southern District of New York, those predicates had been unfairly manufactured by the government to prosecute Rommy in a district that had no actual connection to the charged crime. c. The District Court Did Not Err in Failing to Charge “Manufactured Venue” in Response to the Jury Inquiry Rommy asserts that the district court committed reversible error in failing to include a “manufactured venue” charge in its response to the jury inquiry about outgoing calls. Specifically, Rommy faults the court for not instructing the jury that, if Agent Grey placed telephone calls to Rommy for the purpose of “manufacturing venue” in the Southern District of New York, venue in that district could not be sustained. Rommy’s argument fails for several reasons. First, the district court acted well within its discretion in concluding that the requested instruction was not strictly responsive to the jury’s inquiry as to whether outgoing calls generally, and Agent Grey’s October 17 call in particular, could support venue. While an accused is entitled to have the trial court include in its initial instructions to the jury “any defense theory for which there is a foundation in the evidence,” United States v. Allen, 127 F.3d 260, 265 (2d Cir.1997) (internal quotation marks omitted), a trial court responding to a note from a deliberating jury is only required to answer the particular inquiries posed. The trial court enjoys considerable discretion in construing the scope of a jury inquiry and in framing a response tailored to the inquiry. See United States v. Young, 140 F.3d 453, 456 (2d Cir.1998) (noting that response to jury request “is a matter committed to the sound exercise of a trial court’s discretion”). In doing so, it is not required to reference specific arguments advanced or defenses raised by counsel in urging particular outcomes; cf. Arizona v. Johnson, 351 F.3d 988, 994 (9th Cir.2003) (“Because the jury may not enlist the court as its partner in the factfinding process, the trial judge must proceed circumspectly in responding to inquiries from the jury.”). That conclusion applies with particular force in this case because Rommy argued manufactured venue to the jury without requesting any such instruction from the court in the initial charge. In these circumstances, he can hardly claim reversible error in the district court’s refusal to charge the concept in response to a jury note that did not inquire on that subject. Further, this court has never specifically ruled that a defendant is entitled to a manufactured venue charge. The concept derives from a footnote in United States v. Myers, in which this court did no more than leave open the possibility of invalidating venue in circumstances where the “key events occur in one district, but the prosecution, preferring trial elsewhere, lures a defendant to a distant district for some minor event simply to establish venue.” 692 F.2d at 847 n. 21 (citing United States v. Archer, 486 F.2d 670, 682 (2d Cir.1973) (holding that government agents cannot manufacture federal jurisdiction)); see United States v. Naranjo, 14 F.3d at 147 (rejecting defendant’s claim that government “artificially created venue” in district). Myers itself presented no such venue concern because the “key events” of the crime had, in fact, occurred in the district of prosecution. United States v. Myers, 692 F.2d at 847 n. 21. Thus, we had no occasion conclusively to decide the availability of such a defense, much less the propriety of submitting it to a jury. In the quarter century since Myers, this court has never vacated a conviction on the basis of manufactured venue. Several of our sister circuits, moreover, have specifically rejected or at least questioned the doctrine. See United States v. Rodriguez-Rodriguez, 453 F.3d 458, 462 (7th Cir.2006) (rejecting both manufactured venue and manufactured jurisdiction); United States v. Al-Talib, 55 F.3d 923, 929 (4th Cir.1995) (“There is no such thing as manufactured venue or venue entrapment.” (internal quotation marks omitted)); see also United States v. Spriggs, 102 F.3d 1245, 1250 (D.C.Cir.1996) (expressing reservations as to “manufactured venue”); Andrews v. United States, 817 F.2d at 1279-80 [7th Cir.] (observing that appropriate way to address prosecution venue shopping is through transfer pursuant to Fed.R.Crim.P. 21). However convincing their reasoning, we need not here conclusively decide the continued vitality of the manufactured venue doctrine because the record evidence clearly does not support its application to this case. See United States v. Stewart, 433 F.3d 273, 310 (2d Cir.2006) (holding that refusal to give charge requested by defense does not warrant reversal unless “instruction is legally correct, represents a theory of defense with basis in the record that would lead to acquittal, and the theory is not effectively presented elsewhere in the charge” (internal quotation marks and citations omitted)). Rommy was not “lure[d]” telephonically into the Southern District of New York to pursue a smuggling conspiracy otherwise focused elsewhere. United States v. Myers, 692 F.2d at 847 n. 21. To the contrary, Rommy selected the district as the destination objective of the charged conspiracy. It was he who proposed smuggling ecstasy into New York, first to Bosch and then to DeVries and Agent Grey, telling them that he had confederates in place in New York ready to accept delivery of ecstasy pills. When Bosch expressed a preference to import the pills through Miami, Rommy stated that his New York associates would travel to Florida to arrange for the drugs’ transportation to New York. Rommy reiterated his New York objective to Agent Grey both guardedly in the recorded telephone conversations and bluntly in the videotaped Bermuda meeting. Viewed in this context, Rommy’s five recorded telephone conversations with government actors in New York cannot be viewed as “minor event[s]” engineered “simply to establish venue.” Id. Rather, they were overt acts critical to the furtherance of a criminal scheme that Rommy wished to realize in the Southern District of New York. Accordingly, we identify no error in the district court’s refusal to charge manufactured venue in response to the jury’s venue inquiry. B. Evidentiary Challenges Rommy submits that a number of erroneous evidentiary rulings require reversal of his conviction. Specifically, he asserts that (1) the district court erred in failing to suppress the five telephone calls recorded in New York and the videotape of the meeting in Bermuda as fruits of DEA violations of the Mutual Legal Assistance Treaty (“MLAT”) in effect between the United States and the Netherlands; (2) his post-indictment statements to DEA agents while incarcerated in a Madrid prison should have been suppressed for failure to secure waivers of his Fifth and Sixth Amendment rights; and (3) by allowing the prosecution to read into evidence the transcript of a telephone conversation recorded in 2000 by Dutch authorities, the district court violated Fed.R.Evid. 803(5) and 901(a), as well the Due Process and Confrontation Clauses of the Constitution. None of these arguments warrants reversal. 1. The MLAT Challenge to the Admission of Recorded Evidence Rommy contends that the DEA violated the MLAT in effect between the United States and the Netherlands, as well as Dutch domestic law, by employing a confidential informant (DeVries) to gather evidence in the Netherlands after Dutch officials had denied the United States’ MLAT request to conduct an undercover investigation in their country. Rommy submits that the treaty violation required the district court to suppress all evidence obtained from DeVries’s use as an informant in the Netherlands and all fruits derived therefrom, specifically, the five telephone calls with Rommy in the Netherlands that were, in fact, recorded in New York, and the videotaped meeting between Rommy, DeVries, and Agent Grey in Bermuda. On review of a district court’s ruling on a motion to suppress evidence, we examine findings of fact for clear error, viewing the evidence in the light most favorable to the government, and we apply de novo review to the district court’s conclusions of law. See United States v. Rodriguez, 356 F.3d 254, 257 (2d Cir.2004); United States v. Casado, 303 F.3d 440, 443 (2d Cir.2002). Following these principles, we conclude that Rommy’s treaty argument fails for two reasons. First, Rommy cannot demonstrate a treaty violation. The Treaty on Mutual Assistance in Criminal Matters between the United States and the Netherlands, a self-executing agreement that entered into force in this country on September 15, 1983, see Treaty on Mutual Assistance in Criminal Matters, June 12, 1981, U.S.-Neth., 35 U.S.T. 1361, T.I.A.S. No. 10,734, provides various means for the governments of the two countries to provide legal assistance to one another in criminal matters, see id. art. 1 (describing type of assistance available); see also id. arts. 13-16 (outlining procedures for making and responding to requests for assistance). It also places certain limitations on how information obtained pursuant thereto may be used. See id. art. 11. By its express terms, however, the treaty has no application to evidence obtained outside the MLAT process. Article 18, subsection 1, states: Assistance and procedures provided by this Treaty shall be without prejudice to, and shall not prevent or restrict, any assistance or procedure available under other international conventions or arrangements or under the domestic laws of the Contracting Parties. Id. art. 18, subsec. 1. This does not mean that United States or Dutch authorities, operating without MLAT authorization, may act with impunity in conducting law enforcement investigations in each others’ countries. To the contrary, it means that, when securing evidence without MLAT authorization, foreign government officials lacking diplomatic immunity must conduct themselves in accordance with applicable “domestic laws.” Id. Thus, when DEA agents proceeded to use DeVries as a confidential informant in the Netherlands even after their MLAT request to do so was denied, they did not violate the treaty. They did, however, subject themselves and their informant to any constraints imposed on private actors by Dutch law. We need not here decide whether any DEA actions violated Dutch domestic law. The admissibility of evidence in a United States court depends solely on compliance with United States law. See United States v. Morrison, 153 F.3d 34, 57 (2d Cir.1998) (observing that “federal law governs the admissibility of evidence in a federal criminal trial”); United States v. Brown, 52 F.3d 415, 420 (2d Cir.1995) (noting that “federal law is applicable in a federal prosecution even when state police officers [are] involved” in investigating case); United States v. Pforzheimer, 826 F.2d 200,