Full opinion text
Affirmed by published opinion. Judge TRAXLER wrote the opinion, in which Judge LUTTIG and Senior Judge KISER joined. OPINION TRAXLER, Circuit Judge: Appellants Theresa Squillacote and her husband Kurt Stand appeal from their convictions on various espionage-related charges. We affirm. I. Viewed in the light most favorable to the government, the evidence presented at trial established the following. Kurt Stand’s parents fled to the United States from Germany during Hitler’s reign. After the war, his family maintained contact with friends in the German Democratic Republic (“East Germany”). When Stand was approximately 18, his father introduced him to Lothar Ziemer, an officer with the Ministerium fur Staatssicherheit (“MfS”), East Germany’s intelligence agency. The “HVA” was the foreign intelligence arm of the MfS, and Ziemer was in charge of Section 3 of the HVA’s Department XI. The “primary mission” of Department XI was the “operational reconnaissance of North America.” J.A. 726. Its purpose was to “acquire data of significance to the German Democratic Republic ... that could not be acquired by legal means.” J.A. 726. In the early 1970s, Stand began working for Ziemer as an HVA agent. Stand’s HVA activities consisted primarily of recruiting other agents. In 1976, Stand invited James Michael Clark, a college friend, to travel with him to Germany. Stand introduced Clark to an HVA operative, who introduced him to Ziemer. Ziemer invited Clark to join his organization, which he described as performing intelligence work on behalf of East Germany and other socialist countries, as well as “liberation movements” in Asia, Latin America, and Africa. J.A. 903. Clark agreed. Sometime between 1979 and 1981, Stand brought his wife Theresa Squillacote into the fold, and she too became what Ziemer described as an “informal collaborator[ ].” J.A. 703. At some point, Squillacote’s relationship with Ziemer became more than professional, and they had an affair that lasted until 1996. The HVA devoted substantial resources to the training of Stand, Squillacote, and Clark. They traveled to many countries, including East Germany and Mexico, to meet with their “handlers.” They received training on detecting and avoiding surveillance, receiving and decoding messages sent by shortwave radio from Cuba, mailing and receiving packages through the use of “accommodation” addresses, using codewords and phrases, using a miniature camera to photograph documents, and removing classified markings from documents. HVA records indicate that the three conspirators were together paid more than $40,000 between 1986 and 1989, primarily as reimbursement for travel expenses. As part of his “operational plan” devised -with Ziemer, J.A. 925, Clark moved to Washington, D.C., and obtained a master’s degree in Russian. For a time Clark worked for a private company in a position that required him to obtain a security clearance. He later obtained a position with the United States Army, in its environmental law division, which also required a security clearance. Clark had friends who worked for the State Department, and through them he obtained numerous classified documents that he turned over to the HVA. Squillacote and Stand also moved to Washington, D.C., and she went to law school at the HVA’s suggestion. Squilla-cote first followed in her father’s footsteps by becoming an attorney for the National Labor Relations Board. When she realized that she had taken a career path that was not “in the best direction,” J.A. 2213, she began trying to “move [her] professional work more in line with the commitments that [she] had made.” J.A. 1682. To that end, Squillacote used her father’s connections to obtain an unprecedented temporary detail from the NLRB to the House Armed Services Committee. In 1991, Squillacote obtained a permanent job as an attorney in the Department of Defense, eventually becoming the Director of Legislative Affairs in the Office of the Undersecretary of Defense (Acquisition Reform), a position that required a security clearance and provided access to valuable information. During her tenure with the federal government, Squillacote applied for numerous government jobs, including positions with the Central Intelligence Agency, the National Security Agency, United States Army, Navy, and Air Force, and the Departments of State, Commerce, Energy, and Treasury. Apparently it was not until she began working for the Department of Defense that Squillacote gained access to the kind of information sought by her handlers. However, by that time, East Germany had collapsed. After the fall of the Berlin Wall, Ziemer began working with the KGB, the Soviet Union’s intelligence agency. Ziemer maintained his relationships with Stand, Squil-lacote, and Clark during this time, and they, too, became involved with the KGB. Stand, Squillacote, and Clark each traveled overseas to meet with Ziemer during the period after the collapse of East Germany. Ziemer instructed the conspirators to purchase Casio digital diaries with interchangeable memory cards. The conspirators, Ziemer, and their KGB contacts communicated with each other by exchanging memory cards. In April 1992, Ziemer and another former HVA official were arrested and ultimately convicted for their post-unification intelligence activities with the KGB. Stand, Squillacote, and Clark became understandably concerned about their personal safety after Ziemer’s arrest. They knew that “western services” were looking for two men and one woman operating out of Washington, D.C., and that the western services were aware of code names they had used. J.A. 2240. However, they believed that Ziemer and other former HVA officials would not compromise their identities. When Ziemer was released from prison in September 1992, Stand, Squilla-cote, and Clark re-established a system of communication with him, one purpose of which was to keep everyone informed about any threats to their safety. From the beginning of their involvement with the HVA, Stand, Squillacote, and Clark operated independently of each other and generally were unaware of the others’ activities. After Ziemer’s arrest in 1992, however, the three began talking in detail about their activities and precautions needed to maintain their security. They began discussing the possibility of future intelligence work, perhaps for Vietnam or Cuba. Squillacote also talked to Clark about her interest in South Africa’s Communist Party. In 1994, Squillacote, as part of her search for “another connection,” J.A. 2290, went to Amsterdam to speak to David Truong, whom she had met in college. Truong, who had been convicted of espionage on behalf of North Vietnam, was intrigued, but took no further action. In 1995, Squillacote went to great lengths to obtain a post office box under the name of “Lisa Martin.” In June 1995, SquiUacote, as Lisa Martin, sent a letter to Ronnie Kasrils, the Deputy Defense Minister of South Africa. Kasrils was a Communist party official, and had received training in East Germany, the Soviet Union, and Cuba. The letter, which took SquiUacote months to write, was primarily devoted to SquUlacote’s explanation for the coUapse of socialism that began with the faU of the Berlin Wall, and her views on how the communist movement should proceed in the future. The letter was an attempt by SquUlacote to make a connection with KasrUs, whom SquiUacote hoped would “read between the lines.” J.A.1912. Stand and Clark were aware of the letter, but Clark apparently doubted its effectiveness. In February 1996, SquiUacote received a Christmas card from Kasrils addressed to L. Martin. In the card, Kasrils thanked “Lisa” for “the best letter” he had received in 1995. J.A. 1675. Stand and SquUlacote were thrilled they received the note, and they began to think that perhaps a connection could be made. In September 1996, SquUlacote found another letter from Kas-rUs in her Lisa Martin post office box. The letter stated that “you may have the interest and vision to assist in our struggle,” and invited SquiUacote to a meeting in New York City with a representative of “our special components.” J.A. 1681. SquiUacote and Stand, however, were unaware that, for many years, they had been the subjects of an intense FBI investigation. As part of its investigation, the FBI in January 1996 obtained authorization to conduct clandestine electronic sur-veülance, which included the monitoring of all conversations in the Appellants’ home, as well as calls made to and from their home and SquUlacote’s office. Through its investigation, the FBI had learned of SquUlacote’s letter to Kasrils and the Appellants’ response to the February 1996 note from Kasrils. The September 1996 Kasrils letter in fact was written by the FBI as part of a “false flag” operation intended to uncover information about the prior espionage activities of Stand, Squilla-cote, and Clark. When designing the false flag operation, the FBI’s Behavioral Analysis Program Team prepared a report “to examine the personahty of [SquiUacote] ..., and based on this examination, to provide suggestions ... that could be used in furthering the objective of this investigation — to obtain evidence regarding the subject’s espionage activity.” J.A.2057. The report (the “BAP report”) was based on information the FBI had learned during its extensive investigation and surveillance of the Appellants. The BAP report traced Squillacote’s family background, including the suicide of her older sister and her mother’s history of depression. The report stated that SquUlacote was suffering from depression and listed the anti-depressant medications she was taking. The primary focus of the BAP report, however, was SquUlacote’s emotional makeup and how to taüor the approach to her emotional characteristics. The report described SquiUacote as having “a cluster of personahty characteristics often loosely referred to as ‘emotional and dramatic,’ ” J.A.2060, and recommended taking advantage of Squillacote’s “emotional vulnerability” during her period of grieving over the then-recent end of her affair with Ziemer, using an undercover agent “who possesses the same qualities of dedication and professionalism as her last contact,” and structuring the undercover agent’s “pitch” to mirror her relationship with Ziemer. J.A.2061. The BAP report also made very specific recommendations about how the false flag operation should be designed: The following scenario has been developed upon an analysis of the subject’s personality, and includes suggestions designed to exploit her narcissistic and histrionic characteristics. It is believed that [SquUlacote] will be susceptible to an approach through her mail drop based on her recent rejection by her long-term German handler, and her thrill at receiving a Christmas card from the South African official. J.A.2064. The report suggested the use of a letter from “the object of [Squillacote’s] adulation in South Africa.” J.A.2064. It recommended that the letter instruct Squillacote to travel a circuitous route to the location of the first meeting to “add a sense of excitement and intrigue to the scenario.” J.A.2064. The report recommended the use of a mature male undercover agent, who should “capitalize on [Squillacote’s] fantasies and intrigue” by making a “friendly overture,” and “actfing] professional and somewhat aloof yet responsive to her moods. The initial meet should be brief and leave [Squillacote] beguiled and craving more attention.” J.A. 2065. The false flag letter received by Squilla-cote in September 1996 served its intended purpose. Unaware of any FBI involvement, Squillacote and Stand were thrilled about the letter, and Squillacote began enthusiastically making plans for a trip to New York City to meet the South African emissary. In October 1996, Squillacote met with an undercover FBI agent posing as a South African intelligence officer. She had face-to-face meetings with the agent a total of four times, including one meeting where she brought Stand and her two children. Several letters were also exchanged, including a letter that Squillacote wrote at the request of the undercover agent describing her previous activities with Ziemer. In these meetings and letters, Squilla-cote expressed her enthusiasm for her new South African connection and her hope for a productive collaboration. Throughout her association with the undercover agent, Squillacote discussed the possibility of bringing Ziemer and other former East German contacts into the operation. In December 1996, she contacted Ziemer to see if he was interested in the operation. According to Squillacote, Ziemer’s response was “[y]es, yes, yes, yes, yes!” J.A. 1939. At the second meeting with the undercover agent on January 5,1997, Squillacote presented the agent with four classified documents she had obtained from the Department of Defense. Although the agent had never requested any documents or classified information from Squillacote, she explained that one day when she and her secretary were alone in her office, she decided to “score what [she] could score.” J.A. 509. In fact, she had obtained one of the documents even before her first meeting with the undercover agent. The documents Squillacote gave to the undercover agent were: (1) “Defense Planning Guidance for Fiscal Year 1997 through 2001,” J.A. 499, a numbered document, classified “secret,” with restricted dissemination; (2) “Defense Planning Guidance Scenario Appendix” for 1998 through 2003, J.A. 501, a numbered document classified at the “secret” level, which forbade reproduction or further dissemination without authorization; (3) “Defense Planning Guidance, Fiscal Years 1996 through 2001, Final For Comment Draft,” J.A. 504, which was classified “secret,” with restricted dissemination; and (4) an untitled CIA intelligence report classified “secret,” with restricted dissemination. Three of the documents Squillacote gave to the undercover agent were copies; the “Scenario Appendix” was an original that Squillacote said would not be missed. These documents formed the basis of the charges against Squillacote and Stand. Shortly after this meeting, Squillacote quit her job with the Department of Defense, a political maneuver she hoped would put her in position for a more prestigious job. Nonetheless, Squillacote continued meeting and corresponding with the undercover agent for several more months, until she and Stand were arrested in October 1997. A search of their home uncovered a wealth of incriminating evidence, including a miniature camera, a Casio digital diary and memory cards, and an extra copy of two of the documents given to the undercover agent. Clark eventually pleaded guilty to a single charge of conspiring to commit espionage, and he testified for the government at the trial of Squillacote and Stand. At trial, the government introduced certain HVA records, including “true name” cards showing the names and addresses of Stand, Squillacote, and Clark, as well as documents listing some of their code names and the names of the operations to which they were assigned. The HVA records listed Squillacote as a “[d]evelopmen-tal agent” whose target was the “U.S. central government” and described Squil-lacote as trustworthy. J.A.2028. The records described Stand as reliable, and listed him as a “[s]ource with direct access,” with a target of “U.S. union/organization, direct/upper level, IBFG union, U.S.A.” J.A.2034. Clark was listed as a “[sjource with direct access,” whose activities were targeted against the “Defense Ministry NATO Country FRG USA” J.A. 2010. The records also described Clark as reliable. Other than the four documents passed to the undercover agent, the government presented no evidence establishing that Squillacote or Stand had previously supplied classified documents or information to Ziemer or anyone else. Squillacote and Stand were convicted of conspiracy to transmit information relating to the national defense, see 18 U.S.C.A. § 794(a) and (c) (West 2000); attempted transmission of national defense information, see 18 U.S.C.A. § 794(a); and obtaining national defense information. See 18 U.S.C.A. § 793(b) (West 2000). Squilla-cote was also convicted of making false statements. See 18 U.S.C.A. § 1001 (West 2000). Squillacote and Stand appeal, raising numerous issues arising during the course of the prosecution. We address each issue, although not in the order presented by the Appellants. II. The Appellants filed several pre-trial motions to suppress various portions of the government’s evidence. The district court denied each of the motions, and the Appellants challenge those rulings on appeal. A. The government conducted 550 consecutive days of clandestine surveillance of the Appellants, surveillance that was authorized under the Foreign Intelligence Surveillance Act of 1978 (“FISA”), 50 U.S.C.A. § 1801 — 1811 (West 1991 & Supp.2000). FISA was enacted “to put to rest a troubling constitutional issue” regarding the President’s “inherent power to conduct warrantless electronic surveillance in order to gather foreign intelligence in the interests of national security,” ACLU Found, of Southern California v. Barr, 952 F.2d 457, 460 (D.C.Cir.1991), a question that had not been definitively answered by the Supreme Court. See id. at 461. “FISA thus created a ‘secure framework by which the Executive Branch may conduct legitimate electronic surveillance for foreign intelligence purposes within the context of this Nation’s commitment to privacy and individual rights.’ ” Id. (quoting S.Rep. No. 604, pt. 1, 95th Cong., 1st Sess. 15 (1977), reprinted in 1978 U.S.C.C.A.N. 3904, 3916). FISA established a special court, composed of seven federal district court judges appointed by the Chief Justice, which reviews applications for authorization of electronic surveillance aimed at obtaining foreign intelligence information. See 50 U.S.C.A. § 1803. “With several exceptions not here relevant, electronic surveillance of a foreign power or its agents may not be conducted unless the FISA Court authorizes it in advance.” ACLU of Southern California, 952 F.2d at 461. Each application to the FISA court must first be personally approved by the Attorney General. See 50 U.S.C.A. § 1804(a). The application must contain, among other things, a statement of reasons to believe that the target of the surveillance is a foreign power or agent of a foreign power, specified information on the implementation of the surveillance, and a “certification” from a high-ranking executive branch official stating that the official “deems the information sought to be foreign intelligence information” and that the information sought cannot be obtained by other means. United States v. Pelton, 835 F.2d 1067, 1075 (4th Cir.1987); see 50 U.S.C.A. § 1804(a)(7). Where the target of the surveillance is a “United States person,” the FISA court may issue an order authorizing the surveillance only if the FISA judge concludes that there is “probable cause to believe that the target of the surveillance is a foreign power or agent of a foreign power, that proposed ‘minimization procedures’ are sufficient under the terms of the statute, that the certifications required by § 1804 have been made, and ... that the certifications are not ‘clearly erroneous.’” Pelton, 835 F.2d at 1075; see 50 U.S.C.A. § 1805(a) (setting forth the findings necessary to support the issuance of an order authorizing surveillance). Prior to trial, the Appellants sought to suppress the fruits of the FISA surveillance. They attacked the validity of the surveillance on several grounds, all of which were rejected by the district court. On appeal, however, the Appellants press only one FISA-related issue: They contend that the surveillance was improper because there was no probable cause to believe that Squillacote or Stand were agents of a foreign power. We disagree. Under FISA, an agent of a foreign power is any person who “knowingly engages in clandestine intelligence gathering activities for or on behalf of a foreign power, which activities involve or may involve a violation of the criminal statutes of the United States.” 50 U.S.C.A. § 1801(b)(2)(A). One who knowingly aids and abets another engaging in such clandestine intelligence activities, or one who knowingly conspires with another to engage in the clandestine intelligence activities, is also considered an agent of a foreign power. See 50 U.S.C.A. § 1801(b)(2)(D). A “United States person” may not be determined to be an agent of a foreign power “solely upon the basis of activities protected by the first amendment to the Constitution of the United States.” 50 U.S.C.A. § 1805(a)(3)(A). FISA provides that the district court must review in camera and ex parte the FISA application and other materials necessary to rule upon a defendant’s suppression motion “if the Attorney General files an affidavit under oath that disclosure or an adversary hearing would harm the national security of the United States.” 50 U.S.C.A. § 1806(f). Because the Attorney General filed such an affidavit in this case, the district court reviewed the applications and other materials in camera, and the documents were not disclosed to counsel for the Appellants. See 50 U.S.C.A. § 1806(f) (The district court “may disclose to the aggrieved person, under appropriate security procedures and protective orders, portions of the application, order, or other materials relating to the surveillance only where such disclosure is necessary to make an accurate determination of the legality of the surveillance.”). After reviewing the applications, the district court concluded that each of the more than 20 FISA applications established probable cause to believe that the Appellants were agents of a foreign power. We have reviewed de novo the relevant materials, and likewise conclude that each FISA application established probable cause to believe that Squillacote and Stand were agents of a foreign power at the time the applications were granted, notwithstanding the fact that East Germany was no longer in existence when the applications were granted. See 50 U.S.C.A. § 1801(a) (defining “foreign power”); 50 U.S.C.A. § 1801(b) (defining “agent of a foreign power”). We are also satisfied that the Appellants were not targeted solely because of any protected First Amendment activities in which they may have engaged. Given the sensitive nature of the information upon which we have relied in making this determination and the Attorney General’s conclusion that disclosure of the underlying information would harm the national security, it would be improper to elaborate further. See United States v. Isa, 923 F.2d 1300, 1304 (8th Cir.1991) (finding probable cause to authorize FISA surveillance and declining to comment further on the probable cause issue where the Attorney General filed an affidavit and claim of privilege). Accordingly, we reject the Appellants’ contention that the FISA surveillance was illegal. In addition, because the documents submitted by the government were sufficient for the district court and this Court to determine the legality of the surveillance, we also deny the Appellants’ request for disclosure of the FISA materials. See United States v. Belfield, 692 F.2d 141, 147 (D.C.Cir.1982) (“The language of section 1806(f) clearly anticipates that an ex parte, in camera determination is to be the rule. Disclosure and an adversary hearing are the exception, occurring only when necessary.”). B. The Appellants also sought to suppress the evidence obtained during the search of their home, including the miniature camera, the digital diary and memory cards, a doll with a roll of miniature film hidden inside, and copies of two of the documents Squillacote passed to the undercover agent. The Appellants contend that the search was conducted in flagrant disregard of the express terms of the warrant, and that the district court therefore erred in denying their suppression motion. The warrant authorizing the search of the Appellants’ home stated that the government was to search the residence “on or before October 10, 1997 (not to exceed ten days) ..., serving this warrant and making the search [ ]in the daytime — 6:00 A.M. to 10:00. P.M.” J.A. 330. The search extended over six days, with two FBI agents remaining at the house each night. It is the presence of the FBI agents in the home after 10:00 p.m. that forms the basis of the Appellants’ suppression arguments. (1) The Appellants first contend that, by remaining inside the Appellants’ home overnight for five consecutive nights, the FBI searched the home at night, thus flagrantly disregarding the warrant’s time restriction. We are wholly unpersuaded by this argument. Preliminarily, we reject the main premise of the Appellants’ challenge to the search: that the presence of the agents in the house, in and of itself, constitutes a search that should be considered separate and distinct from the authorized search of the residence. The cases upon which the Appellants rely for this proposition — Segura v. United States, 468 U.S. 796, 104 S.Ct. 3880, 82 L.Ed.2d 699 (1984), and United States v. Jacobsen, 466 U.S. 109, 104 S.Ct. 1652, 80 L.Ed.2d 85 (1984) — involved questions about the nature and propriety of law enforcement conduct that occurred without a warrant. See Segura, 468 U.S. at 799-801, 104 S.Ct. 3380; Jacobsen, 466 U.S. at 111-12, 104 S.Ct. 1652. Thus, a determination of whether the conduct amounted to a search or seizure in those cases was a necessary predicate to the resolution of the Fourth Amendment claims raised. In this case, there is simply no doubt that the government searched the Appellants’ home and seized an abundance of incriminating evidence. The search and seizure, however, were authorized by a warrant, the validity of which the Appellants do not challenge. Where a search is authorized by a warrant, we believe it unnecessary and improper to isolate certain conduct occurring during the execution of the warrant and treat that conduct as a separate and discrete search. Instead, the government’s actions while executing a warrant must be considered in context, and the question that must be answered is whether the government exceeded the scope of the warrant. See, e.g., Walter v. United States, 447 U.S. 649, 656, 100 S.Ct. 2395, 65 L.Ed.2d 410 (1980) (plurality opinion) (“When an official search is properly authorized — whether by consent or by the issuance of a valid warrant — the scope of the search is limited by the terms of its authorization.”). We first conclude that the government did not exceed the scope of the warrant. Second, we conclude that even if the government did exceed the scope of the warrant, blanket suppression of all evidence seized would not be required. (a) Distilled to its essence, the Appellants’ “flagrant disregard” argument is this: (1) The warrant authorized searching the residence only between the hours of 6:00 a.m. and 10:00 p.m.; (2) government agents remained inside the residence between 10:00 p.m. and 6:00 a.m.; (3) ipso facto, the government flagrantly disregarded the terms of the warrant. The validity of this argument, however, is largely dependent upon the Appellants’ assumption that the mere presence of the agents in the house amounted to a search, an assumption we have already rejected. And without this assumption, the argument fails, as we discuss below. When denying the Appellants’ motion to suppress, the district court found that the government complied with the warrant by conducting the search “during the hours that were set out in the warrant.” J.A. 415. This conclusion is supported by the affidavit of Special Agent Gregory Leylegi-an, an FBI agent who took part in the search. Leylegian’s affidavit stated that the FBI “conducted no searching of the premises after 10:00 p.m. each day” and that “[t]he FBI maintained two agents on the premises each night to preserve the integrity of the search process, to expedite the completion of the search, and to maintain security of the premises to prevent the removal or destruction of evidence.” J.A. 360. Because the district court’s factual determination of the conduct actually engaged in by the FBI agents is supported by the evidence presented at the suppression hearing and is not implausible, the standard of review governing this issue dictates that we accept that conclusion. See United States v. Lattimore, 87 F.3d 647, 651 (4th Cir.1996) (en banc) (A district court’s factual determination is clearly erroneous if “it can be said that the view of the evidence taken by the district court is implausible in light of the entire record.”). The warrant provided only that the search must be conducted between the hours of 6:00 a.m. and 10:00 p.m.; it did not expressly prohibit the presence of non-searching agents in the house after 10:00 p.m. Because the FBI did not search during the hours prohibited by the warrant, we therefore conclude that the FBI did not exceed the scope of the warrant by remaining in the house overnight. (b) Nonetheless, even if we were to conclude that the FBI exceeded the scope of the warrant, we still would not conclude that the government’s actions required suppression of all the evidence seized during the search. As a general rule, if officers executing a search warrant exceed the scope of the warrant, only the improperly-seized evidence will be suppressed; the properly-seized evidence remains admissible. See United States v. Jones, 31 F.3d 1304, 1314 (4th Cir.1994); see also Horton v. California, 496 U.S. 128, 140, 110 S.Ct. 2301, 110 L.Ed.2d 112 (1990) (“If the scope of the search exceeds that permitted by the terms of a validly issued warrant or the character of the relevant exception from the warrant requirement, the subsequent seizure is unconstitutional without more. Thus, in the case of a search incident to a lawful arrest, if the police stray outside the scope of an authorized ... search they are already in violation of the Fourth Amendment, and evidence so seized will be excluded .... ” (emphasis added) (alteration and internal quotation marks omitted)). However, “[i]n extreme circumstances even properly seized evidence may be excluded when the officers executing the warrant exhibit a flagrant disregard for its terms.” United States v. Ruhe, 191 F.3d 376, 383 (4th Cir.1999) (internal quotation marks omitted). The extraordinary remedy of blanket suppression of all evidence seized “should be used only when the violations of the warrant’s requirements are so extreme that the search is essentially transformed into an impermissible general search.” United States v. Chen, 979 F.2d 714, 717 (9th Cir.1992); accord United States v. Medlin, 842 F.2d 1194, 1199 (10th Cir.1988). Thus, in the few cases where blanket suppression has been ordered, most involved the seizure by law enforcement officials of large quantities of evidence clearly not within the scope of the warrant. See United States v. Foster, 100 F.3d 846, 848 (10th Cir.1996); Medlin, 842 F.2d at 1196, 1199; United States v. Rettig, 589 F.2d 418, 420-21 (9th Cir.1978). In this case, however, the Appellants do not contend that any of the evidence seized by the government was beyond the scope of the warrant or that, by remaining in the house after 10:00 p.m., the government impermissibly converted the warrant into a general warrant. Instead, the Appellants complain only about the manner by which the government executed the warrant, a complaint that is inadequate to justify the severe remedy of blanket suppression. First, we note that when a warrant authorizes only a daytime search, some courts have held that there is no violation of the terms of the warrant if the search is commenced in the daytime, even if it continues into the night. See, e.g., United States v. Young, 877 F.2d 1099, 1104-05 (1st Cir.1989); United States v. Burgard, 551 F.2d 190, 193 (8th Cir.1977); United States v. Joseph, 278 F.2d 504, 505 (3rd Cir.1960) (per curiam). Because the search of the Appellants’ home was commenced in the daytime, as required by the warrant, the FBI agents reasonably could have believed (if their actions after 10:00 p.m. could be considered a search) that it was proper to continue the search into the night. Second, the FBI reasonably could have concluded that it was proper to station agents inside the house after the search was suspended each evening in order to guard against the possible destruction of evidence. Cf. United States v. Gagnon, 685 F.2d 766, 769 (10th Cir.1980) (concluding that when agents executing a search warrant discovered more marijuana than they could transport, the agents were responsible for preserving the evidence, and properly remained on the scene overnight and resumed the search the next day, when a truck arrived that could carry away the drugs). The reasonableness of the agents’ conduct makes it difficult to conclude that they flagrantly disregarded the terms of the warrant. Under these circumstances, even if the FBI’s actions amounted to technical violations of the terms of the warrant, the violations were relatively minor and were “motivated by considerations of practicality rather than by a desire to engage in indiscriminate ‘fishing.’ ” United States v. Tamura, 694 F.2d 591, 597 (9th Cir.1982). Thus, any violations are wholly insufficient to require blanket suppression of all the evidence seized under the warrant. (2) In a last-ditch effort to invalidate the search, the Appellants contend that if the government did in fact stop searching each night at 10:00, then the evidence must still be suppressed because the government did not obtain a new warrant for each successive day of searching. Again we disagree. It is beyond dispute that FBI agents entered the Appellants’ home on six consecutive days to search for evidence. However, given the number and type of items that can be evidence of espionage-related activities, the search was necessarily extensive and exhaustive. See United States v. Wuagneux, 688 F.2d 1343, 1352 (11th Cir.1982) (“[T]he magnitude of a search is insufficient, by itself, to establish a constitutional violation; rather, the relevant inquiry is whether the search and seizures were reasonable under all the circumstances .... [GJiven the complexity of the crimes under investigation and the fact that they would be detected primarily if not exclusively through analysis and synthesis of a large number of documents, a rather extensive search could reasonably be expected.”). As Agent Leylegian explained in his affidavit, a “search for evidence of espionage ... requires extreme thoroughness in order to discover the covert instruments, communications, and records of the illegal activity.” J.A. 358. In addition, the search was complicated by the condition of the home. According to Leylegian, “[t]he house was extremely cluttered, and the [Appellants’] personal possessions and documents were of such quantity and in such a state of disarray as to create a great obstacle to the execution of the warrant.” J.A. 359. The search was further complicated because the house was undergoing renovations, which increased the clutter and made it difficult to search certain areas of the house. Leylegian also explained that the agents were unable to search the basement, where many items were located, “for long stretches of time due to the irritation caused by an immense amount of dust and the odor of cat urine.” J.A. 360. Therefore, notwithstanding the large number of agents involved in the search, it is apparent that the search could not have been completed in a single day. Under these circumstances, the subsequent entries were not separate searches requiring separate warrants, but instead were simply reasonable continuations of the original search. The government, therefore, was not required to obtain additional warrants for each day that the search continued. See United States v. Kaplan, 895 F.2d 618, 623 (9th Cir.1990) (concluding that second search conducted two hours after first search was a proper continuation of the first search); United States v. Carter, 854 F.2d 1102, 1107 (8th Cir.1988) (upholding under a single warrant a second search occurring several hours after initial search: “The authority of the warrant had not expired and therefore the return search was not beyond the scope of the Fourth Amendment.”); United States v. Bowling, 351 F.2d 236, 241 (6th Cir.1965) (upholding entries on successive days pursuant to a single warrant); see also United States v. Gerber, 994 F.2d 1556, 1558-60 (11th Cir.1993) (reversing the suppression of evidence found on Monday during search under the hood of a car even though warrant authorizing the search of the car expired on the previous Friday). Although this search may well have extended over a substantially longer period of time, the length of the search was a function only of the nature of the evidence sought and the condition of the home. To require the government to obtain a new search warrant for each continued day of searching would impose an undue burden on the government’s efforts to investigate complex crimes, a burden that would be unjustifiable under the circumstances of this case. See United States v. Sakyi, 160 F.3d 164, 167 (4th Cir.1998) (“The touchstone of our analysis under the Fourth Amendment is always the reasonableness in all the circumstances of the particular governmental invasion of a citizen’s personal security. Reasonableness is determined by weighing the public interest against the individual’s right to personal security free from arbitrary interference by law officers.” (citations and internal quotations omitted)). Accordingly, we conclude that the district court properly denied the Appellants’ motion to suppress the evidence obtained during the search of their house. C. During the FISA-authorized surveillance of the Appellants, the government intercepted several telephone calls between Squillacote and her psychotherapists. Only the first two of these conversations, however, were listened to or transcribed by the government. Once the supervising FBI agent learned of the conversations, she instructed the agent responsible for transcribing and indexing the conversations not to listen to, index, or transcribe any other conversations between Squillacote and her therapists. The Appellants moved to suppress any evidence derived from the privileged communications, and requested a hearing to require the government to prove that the evidence it would present at trial was derived from sources independent of the privileged communications. The district court refused to hold the hearing, concluding that such a hearing was required only when a constitutionally-based privilege was at issue. On appeal, the Appellants contend that the FBI employee who listened to and transcribed the conversations between Squillacote and her therapists was involved in the preparation of Squillacote’s BAP report, and that privileged information was therefore used to formulate the false flag operation that led to the arrest of the Appellants. The Appellants contend that any evidence derived from the privileged information should have been suppressed and that they were entitled to a hearing to vindicate the principles set forth by the Supreme Court in Kastigar v. United States, 406 U.S. 441, 92 S.Ct. 1653, 32 L.Ed.2d 212 (1972). We, however, conclude that Kastigar simply is not applicable to this case. In Kastigar, the issue was whether a witness who asserts his Fifth Amendment privilege against self-incrimination may be compelled to testify “by granting immunity from the use of compelled testimony and evidence derived therefrom (‘use and derivative use’ immunity), or whether it is necessary to grant immunity from prosecution for offenses to which compelled testimony relates (‘transactional’ immunity).” Id. at 443, 92 S.Ct. 1653. The Court concluded that a grant of “immunity from use and derivative use is coextensive with the scope of the privilege against self-incrimination, and therefore is sufficient to compel testimony over a claim of the privilege.” Id. at 453, 92 S.Ct. 1653. The Court noted that if a witness who has been granted use and derivative use immunity is subsequently prosecuted, the prosecutors bear “ ‘the burden of showing that their evidence is not tainted by establishing that they had an independent, legitimate source for the disputed evidence.’ ” Id. at 460, 92 S.Ct. 1653 (quoting Murphy v. Waterfront Comm’n of New York Harbor, 378 U.S. 52, 79 n. 18, 84 S.Ct. 1594, 12 L.Ed.2d 678 (1964)). The Court further explained that “[t]his total prohibition on use provides a comprehensive safeguard, barring the use of compelled testimony as an ‘investigatory lead,’ and also barring the use of any evidence obtained by focusing investigation on a witness as a result of his compelled disclosures.” Id. at 460, 92 S.Ct. 1653 (footnote omitted). We agree with the Appellants that Squillacote’s conversations with her psychotherapists are privileged. See Jaffee v. Redmond, 518 U.S. 1, 15, 116 S.Ct. 1923, 135 L.Ed.2d 337 (1996) (“[W]e hold that confidential communications between a licensed psychotherapist and her patients in the course of diagnosis or treatment are protected from compelled disclosure under Rule 501 of the Federal Rules of Evidence.”). The question, then, is whether the mere existence of this privileged information brings to bear the full weight of Kastigar, as Appellants apparently contend. Contrary to the Appellants’ view, a Kastigar analysis is not triggered by the existence of evidence protected by a privilege, but instead by the government’s effort to compel a witness to testify over the witness’s claim of privilege. See United States v. Hubbell, — U.S. -, -, 120 S.Ct. 2037, 2045, 147 L.Ed.2d 24 (2000) (stating that Kastigar “particularly emphasized the critical importance of protection against a future prosecution based on knowledge and sources of information obtained from the compelled testimony ” (emphasis added) (internal quotation marks omitted)); United States v. McHan, 101 F.3d 1027, 1035 (4th Cir.1996) (“Whether the oral use-immunity agreement at issue in this case is subject to the full Kastigar protections is doubtful because McHan voluntarily cooperated -with the government.”); United States v. Eliason, 3 F.3d 1149, 1152 (7th Cir.1993) (Under Kastigar, “if a defendant is able to establish through relevant evidence that he gave compelled testimony in a court proceeding based upon a promise of immunity, the government must come forth with evidence that the information it purports to use against the defendant came from a source independent of the defendant’s immunized testimony.”); United States v. Gutierrez, 696 F.2d 753, 756 n. 6 (10th Cir.1982) (“Because [the defendant], with full knowledge of her rights, voluntarily agreed to make a statement, the constitutional principles enunciated in Kastigar ... are inapplicable to her claim.”). If the privilege can be vindicated through a grant of immunity — as can, for example, the privilege against self-incrimination — then the witness may be compelled to testify if an adequate offer of immunity is made. To this extent then, we agree with the Appellants’ assertion that Kastigarlike protections may be required in cases involving testimony compelled over the assertion of a non-constitutional privilege. For example, a spouse asserting the adverse spousal testimony privilege or the marital communications privilege may be compelled to testify if the prosecutor gives an adequate promise that the information will not be used against the other spouse. See, e.g., In re Grand Jury, 111 F.3d 1083, 1087 (3rd Cir.1997) (“[0]nce the government grants immunity that eliminates the possibility that the testimony will be used to prosecute the witness’s spouse, the witness spouse may no longer invoke the testimonial privilege.”); In re Grand Jury Subpoena of Ford, 756 F.2d 249, 252 (2nd Cir.1985) (concluding that husband could be held in contempt for refusing to testify before the grand jury about actions of his wife where the prosecutor promised that “no grand jury testimony elicited from [the husband] would be used, either directly or indirectly, against [his] wife”). However, because the government’s right to compel testimony in the face of a claim of privilege is the issue at the heart of Kastigar, its protections do not apply in cases where there is privileged evidence, but no compelled testimony. Moreover, because “[testimonial exclusionary rules and privileges contravene the fundamental principle that the public ... has a right to every man’s evidence,” any such privilege “must be strictly construed.” Trammel v. United States, 445 U.S. 40, 50, 100 S.Ct. 906, 63 L.Ed.2d 186 (1980) (ellipses in original) (citation and internal quotation marks omitted). Thus, we do not believe that suppression of any evidence derived from the privileged conversations would be proper in this case, given that the privilege is a testimonial or evidentiary one, and not constitutionally-based. See United States v. Elie, 111 F.3d 1135, 1142 (4th Cir.1997) (rejecting defendant’s claim that evidence found as a result of his custodial statements made without receiving Miranda warnings should be suppressed because “the ‘tainted fruits’ analysis applies only when a defendant’s constitutional rights have been infringed”). Other circuits have rejected similar arguments under similar circumstances. For example, in United States v. Marashi, 913 F.2d 724 (9th Cir.1990), the court concluded that the testimony of the defendant’s ex-wife was not barred by the marital communications privilege, and the court therefore declined to address the defendant’s argument that all evidence derived from the ex-wife’s information and testimony should be suppressed. See id. at 731 n. 11. The court noted, however, that “no court has ever applied the [fruit-of-the-poisonous-tree] theory to any evidentiary privilege.” Id.; see also Nickel v. Hannigan, 97 F.3d 403, 409 (10th Cir.1996) (even if testimony of attorney consulted by the defendant before the defendant was charged with a crime should have been suppressed on the basis of a breach of the attorney-client privilege, evidence obtained by the police that was derived from the attorney’s information should not have been suppressed); United States v. Lefkowitz, 618 F.2d 1313, 1318 n. 8 (9th Cir.1980) (“Because we reject ... Lefkowitz’s argument that the marital privileges are somehow constitutionally grounded in, among other locations, the Fourth Amendment, we doubt that a secondary source of information obtained through information protected by the confidential marital communications privilege would in any way be ‘tainted.’ ”). Because this case does not involve the use of compelled testimony, the district court properly refused the Appellants’ request for a Kastigar hearing. In addition, because the privilege at issue here is not a constitutional one, the district court properly refused to suppress any evidence arguably derived from the government’s interception of the two conversations with Squillacote’s therapists. III. Perhaps some of the most damaging evidence introduced against the Appellants at trial were the HVA documents — the “true name” cards listing the names of the Appellants and their code names, and the “agent data sheets” showing the nature of their assignments for the HVA. The Appellants moved to prevent the introduction of these documents, but the district court denied the motion. On appeal, the Appellants contend that the documents were improperly admitted, arguing that they were not properly authenticated and that, even if authenticated, the documents were inadmissible hearsay. A. The Federal Rules of Civil Procedure provide that official records of a foreign country are considered properly authenticated if the records are attested by a person authorized to make the attestation, and accompanied' by a final certification as to the genuineness of the signature and official position (i) of the attesting person, or (ii) of any foreign official whose certificate of genuineness of signature and official position relates to the attestation or is a chain of certificates of genuineness of signature and official position relating to the attestation. Fed.R.Civ.P. 44(a)(2). “A final certification may be made by a secretary of embassy or legation, consul general, vice consul, or consular agent of the United States, or a diplomatic or consular official of the foreign country assigned or accredited to the United States.” Id. Rule 902(3) of the Federal Rules of Evidence sets forth an essentially identical self-authentication process for the somewhat broader category of “foreign public documents” “purporting to be executed or attested in an official capacity” by a foreign official. See Fed. R.Evid. 902(3); id. advisory committee’s note (Rule 902(3) “is derived from Rule 44(a)(2) of the Rules of Civil Procedure but is broader in applying to public documents rather than being limited to public records”). In this case, the government presented a certification from Dirk Dorrenberg, the director of the counterespionage and protective security department of the Bundesamt fur Verfassungsschutz, the counter-intelligence service for the unified Federal Republic of Germany (“FRG”). In his certification Dorrenberg stated that the FRG is the legal successor to East Germany and that he had the “authority to make this certification by virtue of [his] official position and area of expertise.” 'J.A.1982. Dorrenberg stated that he had compared the HVA documents introduced by the government to “actual duplicates” of the original records, and he certified that the government’s copies were “true and correct copies” of “genuine and authentic records” of the HVA. J.A.1983-84. Dorren-berg also certified that the signature of Lothar Ziemer appearing on some of the records was “genuine and authentic.” J.A. 1984. The government also presented a final certification from Manfred Bless, an FRG representative “assigned and accredited to the United States as a Counselor, Political Section, of the Embassy of the Federal Republic of Germany, in Washington, D.C.” J.A.1980. In this final certification, Bless certified that Dorrenberg held the position claimed in the Dorrenberg certification and that Dorrenberg was authorized to make the certification. These certifications comply in all respects with the requirements of ‘ Rule 44(a)(2) and Rule 902(3). Therefore, whether the documents are considered official documents or official records, the district court quite properly concluded that the government adequately authenticated the HVA documents. The Appellants, however, contend that the certification process of Rule 902(3) is intended to confirm the signature or attestation contained in the offered document. According to the Appellants, if the document being offered into evidence does not contain a signature, a self-serving declaration of authenticity is meaningless. Thus, the Appellants contend that many of the HVA documents are not subject to self-authentication under the rules because the documents themselves are not signed or do not contain an attestation. This argument is without merit. Nothing in Rule 44(a)(2) or in Rule 902(3) requires that the documents themselves be signed or contain an attestation within the body' of the document. The rules are written in the alternative — foreign documents may be authenticated by a certification from the official executing the document or by an official attesting to the document. To “attest” means to “affirm to be correct, true, or genuine.” American Heritage College Dictionary 89 (3d ed.1997). Thus, so long as a proper official attests that the proffered document is true and genuine, it simply does not matter whether the document itself is signed or contains its own attestation. As noted above, Rule 44(a)(2) also requires a final certification regarding the signature and position “(i) of the attesting person, or (ii) of any foreign official whose certificate of genuineness of signature and official position relates to the attestation or is in a chain of certificates of genuineness of signature and official position relating to the attestation.” Fed.R.Civ.P. 44(a)(2); see also, Fed.R.Evid. 902(3)(A) & (B). Seizing on these requirements, the Appellants contend that neither the Dorrenberg certification nor the Bless certification establish that “Dorrenberg is an official ‘whose certificate of genuineness of signature and official position relates to the execution or attestation’ or that his certificate is in a ‘chain of certificates of genuineness of signature and official position relating to the execution or attestation.’ ” Brief of Appellants at 73. This argument is likewise without merit, as it is premised upon a fundamental misapprehension of the requirements for the authentication of foreign documents. An examination of Rule 44(a)(2) and Rule 902(3) reveals two requirements for the authentication of a foreign document. First, there must be some indication that the document is what it purports to be. Thus, the proffered document must be executed by a proper official in his official capacity, or the genuineness of the document must be attested to by a proper official in his official capacity. See Fed. R.Civ.P. 44(a)(2); Fed.R.Evid. 902(3); see also United States v. Doyle, 130 F.3d 523, 545 (2d Cir.1997) (noting that the authentication provisions of the Rules of Evidence are not concerned with establishing the truth of information contained in proffered documents, but only with “assuring that evidence is what it purports to be”). Second, there must be some indication that the official vouching for the document is who he purports to be. Thus, the rules require that one of a specified group of foreign officials must issue a final certification attesting to the genuineness of signature and title of the person executing or attesting to the document, or of another official who has certified the signature and position of the person executing or attesting to the document. By the plain language of the rules, it is only when the genuineness of signature and position is established in the second manner described above that it is relevant whether the official is “relatefd] to” the execution or attestation or is in the “chain of certificates of signature and position.” See Fed R. Civ. P. 44(a)(2); Fed.R.Evid. 902(3). In this case, the government satisfied the first requirement of establishing that the HVA records were what they purported to be by presenting Dorrenberg’s certification that the government’s records were true and accurate copies of genuine HVA records. The government then established that the official vouching for the document was who he purported to be in the first manner described above — by presenting a final certification from another official establishing that it was Dorren-berg’s signature on the proffered certification and that Dorrenberg was authorized to attest to the authenticity of the HVA documents. Because the government established the genuineness of signature and position of the person attesting to the documents, the portions of the rules dealing with officials related to the execution or attestation or in the chain of certifications are not applicable. Finally, contrary to the Appellants’ suggestions, the rules do not require the official attesting to the genuineness of foreign documents or records to have possession or custody of the proffered documents, to be an expert in handwriting analysis, or to have been associated with the foreign government at the time the documents were created. See Fed.R.Civ.P. 44(a)(2); Fed.R.Evid. 902(3). Accordingly, we conclude that the government properly authenticated the HVA records, whether the authentication is considered under Rule 44(a)(2) of the Rules of Civil Procedure or under Rule 902(3) of the Rules of Evidence. Cf. United States v. Koziy, 728 F.2d 1314, 1322 (11th Cir.1984) (concluding that World War II-era employment forms showing the defendant’s affiliation with the Ukranian police, during a period when Russia was in control of the region, were properly authenticated under Fed.R.Evid. 902(3) where the documents were attested to by “[a] Russian official authorized to authenticate such documents”). B. The Appellants also challenge the district court’s ruling that the HVA documents were admissible as statements of a co-conspirator under Rule 801(d)(2)(E) of the Federal Rules of Evidence. We review the district court’s admission of evidence under Rule 801(d)(2)(E) for an abuse of discretion. See United States v. Blevins, 960 F.2d 1252, 1255 (4th Cir.1992). Evidence that would otherwise be considered hearsay may be admitted as a statement by a co-conspirator if the government establishes, by a preponderance of the evidence, “(1) that there was a conspiracy involving the declarant and the party against whom admission of the evidence is sought and (2) that the statements at issue were made during the course of and in furtherance of that conspiracy.” Id.; see also Bourjaily v. United States, 483 U.S. 171, 175, 107 S.Ct. 2775, 97 L.Ed.2d 144 (1987). In our view, the district court properly admitted the HVA records as statements by a co-conspirator. First, ' the indictment specifically charged the Appellants with conspiring with, among others, “agents and officers of the GDR,” J.A. 88, and the government presented ample evidence supporting that allegation, including the government’s overwhelming evidence of the Appellants’ relationship with Lothar Ziemer, whose signature appears on many of the disputed HVA documents. Second, although some of the documents are undated, many bear dates that are clearly within the course of the conspiracy as defined by the government’s evidence. And many of the undated HVA documents show the same registration number as the dated documents and the documents bearing Ziemer’s signature, thus establishing a connection between all of the HVA documents. Accordingly, the government’s evidence demonstrated that' the statements were made during the course of the conspiracy. Third, there can be no real dispute that, by compiling the information contained in the disputed documents — the Appellants’ real and code names, their addresses, the object of their assignments, how they could be contacted — the GDR was acting in furtherance of the conspiracy. While the identity of the declarant of the unsigned documents may not be known, the only conclusion that can be drawn from the information included in the documents — information that was corroborated in many respects by Clark’s testimony and by Squillacote’s own statements to the undercover agent — is that the documents were created by or at the direction of East German agents who had knowledge of and were involved in the conspiracy with the Appellants. While there may be cases where the inability to identify the declar-ant of an alleged co-conspirator’s statement could render the statement inadmissible, this is not one of those cases. The HVA documents were sufficiently connected to each other and to the .conspiracy established by the government’s evidence to make them reliable and admissible under Rule 801(d)(2)(E), notwithstanding the government’s inability to identify the de-clarants. See United States v. Cruz, 910 F.2d 1072, 1081 n. 10 (3d Cir.1990) (“Uni-dentifíability [of the declarant] may be important in some situations, but when the statement itself and the surrounding circumstances provide sufficient evidence of reliability, unidentifiability will not be particularly important.”). We therefore conclude that the HVA records were properly authenticated and were properly admitted as statements of co-conspirators. The Appellants’ complaints about the reliability