§ 3.05. Notice to Courts and Targets of Investigations

(a) Agency requests for a court order or warrant should identify the policing activities used to obtain the information underlying the request, as well as the methods and techniques to be used in executing the order requested.

(b) In cases in which the target is prosecuted, the agency or prosecutor should inform the target about any policing activities that produced evidence against the target.

(c) In a case in which the target is not prosecuted, the agency should inform the target of any particularly invasive methods or techniques that were used to gather information about the individual, although the agency may delay providing notice in so far as it would impede an ongoing investigation of either the individual or the broader criminal enterprise of which the individual is believed to be a part.


a. Generally. This Section serves a number of important purposes. First, it enables courts to fulfill their constitutional obligation to define the scope of the Fourth Amendment and to supervise adequately searches and seizures that fall within the Fourth Amendment’s reach. Second, it ensures that criminal defendants are afforded their due-process right to review the evidence against them and to challenge the use of any evidence that may have been obtained improperly. Third, it ensures that individuals are made aware of—and are able to challenge—governmental intrusions into their lives and property. These purposes are imperiled when agencies conceal from courts and from targets of government searches, particularly criminal defendants, the tactics they used or intend to use to obtain information. See also § 3.02 (discussing aggregate disclosure to the broader public).

In any number of instances, judges have expressed serious concerns that relevant information was kept from them. Such information includes the methods agency officials intended to use to execute a court order or warrant and the means by which agency officials gathered evidence to support the court order or warrant in the first place. For example, in warrant applications to search a particular address or location where the defendant was found, agencies sometimes have alluded to nonexistent confidential sources in lieu of disclosing the actual techniques, such as Stingray cell-site simulators, they used to locate the defendant. Law-enforcement officials also have relied on what sometimes is referred to as “parallel construction”, which involves working backward to develop an alternative path for obtaining information or evidence in order to avoid disclosing how officials originally came upon it. Similarly, agencies, in requesting court orders and warrants, have at times not provided judges with full and candid information about the means by which officers intended to execute the order. Tactics such as these undermine the legitimacy of judicial proceedings, breed mistrust among judges regarding law-enforcement officers, and run the risk of circumventing constitutional or other protections.

b. Reasons to notify judges. Notice to judges is necessary to enable judges to perform the functions required of them by statutes and the Constitution. Court orders and warrants have evidentiary predicates, be they “relevance” to a legitimate investigation or “probable cause”; and judges have an obligation to assess independently whether the predicate has been met. Judges need to know the means by which the information was obtained in order to ensure that it is reliable and was obtained lawfully. The warrants themselves must describe with “particularity” the places to be searched and the items that may be seized. In order to be specific about what is permitted pursuant to a warrant, judges need to know what the requesting agency intends to do to execute it. This sort of notice is particularly important when an agency plans to seize computers or records that contain vast amounts of information—not only about the target but also potentially third persons. The same is true of certain forms of digital surveillance, which necessarily sweep up information about many people at once. Judicial supervision is essential to ensure that agency officials are taking the steps necessary to both minimize the collection of information that exceeds the scope of the investigation and regulate the use of any incidental records that are inadvertently obtained. See also § 3.03 (on limiting the scope of information-gathering activities).

c. Notice to individuals who subsequently are prosecuted. There are independent reasons to notify the targets of government information gathering. The most obvious apply to targets who subsequently become criminal defendants. Those individuals have a right to know how information about them was acquired so that they may challenge the lawfulness of the procedures used. They also have a due-process right to assure any evidence against them is reliable and to know of any possible exculpatory evidence, both of which may be implicated by the methods of information collection. Courts have long held that the government’s interest in preserving confidentiality must give way when the information at issue is material to the defense. Because few issues are more central to the defense than the question of whether evidence was obtained lawfully and is therefore admissible against the accused, it is particularly important that this information be disclosed.

This does not mean that the government necessarily must reveal every detail about a particular technology or technique used. For example, courts have held that the government need not disclose the precise placement of an electronic-surveillance device or the precise technical specifications for a piece of equipment. But agencies should, at a minimum, provide sufficient information to enable defendants to address the accuracy or lawfulness of the investigative techniques that were used.

d. Notice to targets who are not prosecuted. Agencies also should—at least in some circumstances—provide notice to individuals who are the targets of information-gathering activities but who are not prosecuted. Under the Federal Rules of Criminal Procedure, as well as analogous state rules, agencies already are required to notify the targets of all searches and surveillance activities conducted pursuant to a warrant, although notice may be delayed to prevent flight, the destruction of evidence, or harm to witnesses. In some cases, individuals also must be notified when the government obtains information about them from third parties. See § 2.05 (addressing notice to targets of third-party information gathering). Such notice provisions ensure that individuals have an opportunity to challenge the legality of government intrusions into their lives and promote the broader systemic goal of ensuring the propriety and legality of government action.

A more difficult question arises with regard to information-gathering activities that are not conducted pursuant to a warrant or a court order. A blanket presumption in favor of providing notice of all information-gathering activities—every license-plate scan or query made of another agency’s database—would impose an immense administrative burden on law enforcement. At least some of the information-gathering techniques that are subject to these Principles are minimally intrusive. In addition, many are used in the early stages of an investigation, long before it is clear whether or when an individual will in fact be prosecuted. Enterprise investigations in particular may take a long time to come to fruition. For at least some information-gathering activities, then, aggregate notice to the public, along with robust auditing by the agency itself, see § 3.02, may be sufficient to ensure that these techniques are used responsibly. However, for more intrusive information-gathering activities—including comprehensive data requests from third parties, trash drops, or long-term physical surveillance—notice may indeed be appropriate, and legislatures and agencies ought to consider requiring it, subject to the same sorts of delay provisions that apply to warrant-based searches.

e. Need for confidentiality. Any exceptions to disclosure requirements should be construed narrowly and generally limited to circumstances in which disclosure would lead to specific and articulable harms, such as retaliation against confidential sources. Generalized concerns that public awareness of a particular technology could eventually lead to attempts to circumvent or avoid it typically are not sufficient to justify withholding material information from courts. And certainly, agencies themselves should not be the ones to strike that balance unilaterally. A variety of strategies, including submitting documents under seal, may be used to avoid widespread disclosure while giving courts the information that they need in order to fulfill their constitutional role.

Reporters’ Notes

1. Established law. Many of the propositions in this Section are matters of established law. For example, in Franks v. Delaware, the U.S. Supreme Court held that criminal defendants have a right to challenge warrants as being based on false statements made by officers in obtaining them—a right that defendants cannot exercise if critical information is kept out of warrant applications. 438 U.S. 154, 155-1556 (1978); see also United States v. Ferguson, 758 F.2d 843, 848 (2d Cir. 1985) (applying Franks to material omissions from affidavits as well); Olson v. Tyler, 771 F.2d 277, 281 n.5 (7th Cir. 1985) (same). Similarly, in Roviaro v. United States, the Court held that defendants are entitled to know the identity of confidential informants when that information is material to their defense. 353 U.S. 53, 62 (1957). Courts have applied similar principles to require disclosure of the nature or location of surveillance activity. See, e.g., United States v. Foster, 986 F.2d 541, 543 (D.C. Cir. 1993) (holding that defendant demonstrated need for disclosure of observation spot from which officer observed drug transaction in order to challenge officer’s ability to identify defendant accurately); see also 18 U.S.C. § 2518(9) (Wiretap Act prohibition of use of intercepted communications against defendant unless defendant is provided copy of warrant application that resulted in court order). Similarly, notice to targets of warrant-based searches is mandated by Rule 41 of the Federal Rules of Criminal Procedure, as well as by analogous rules in various states. Fed. R. Crim. P. 41(f)(1)(C); see, e.g., Cal. Penal Code § 1535 (providing for notice of property seized pursuant to warrant), § 1546.2 (providing for notice of execution of warrant for electronic information); Idaho Court Rule 41(e)(2); Minn. Stat. Ann. § 626.16; Wyo. R. Crim. P. 41(f)(1)(C). A number of federal and state statutes likewise require notice be provided to targets when agencies seek to obtain certain kinds of information from third parties. See, e.g., Video Privacy Protection Act, 18 U.S.C. § 2710(b)(3) (requiring prior notice to customer if videotape-service provider discloses personally identifiable information to law enforcement).

Courts also have held in various contexts that in order to comply with the Fourth Amendment’s particularity requirements, search-warrant applications must, at least in some circumstances, disclose the manner in which a search is to be conducted. See, e.g., In re Search of Apple iPhone, 31 F. Supp. 3d 159, 166 (D.D.C. 2014) (denying search-warrant application for cellphone because it lacked sufficient search protocol); United States v. Phua, 2015 WL 1281603, at *7 (D. Nev. Mar. 20, 2015) (denying search-warrant applications for cellphones and iPads because they lacked search protocols). This is particularly true in the context of computer searches and searches of third-party databases, for which courts may need additional information in order to ensure that the search they are authorizing does not exceed its permissible scope. See United States v. Galpin, 720 F.3d 436, 447 (2d Cir. 2013) (noting that “[t]he potential for privacy violations occasioned by an unbridled, exploratory search of a hard drive is enormous,” which “demands a heightened sensitivity to the particularity requirement”); United States v. Comprehensive Drug Testing, Inc., 621 F.3d 1162, 1177 (9th Cir. 2010) (emphasizing that because government searches of databases “have the potential to expose exceedingly sensitive information about countless individuals not implicated in any criminal activity,” the interests of everyone “are best served if there are clear rules to follow”); Paul Ohm, Massive Hard Drives, General Warrants, and the Power of Magistrate Judges, 97 Va. L. Rev. Brief 1, 40 (2011) (comparing computer-search warrants to general warrants and concluding that courts can fulfill their constitutional duty only by imposing ex ante restrictions on execution of computer warrants). This same principle applies when police request to use novel search technologies and techniques—such as Stingrays and cell-tower dumps—that have the potential to sweep in data belonging to individuals who are unrelated to the case. See In re Application of U.S. for Warrant, 2015 WL 6871289, at *3 (N.D. Ill. 2015) (imposing requirements for use of cell-site simulator to address “collection of innocent third parties’ information”); In re U.S. ex rel. Order Pursuant to 18 U.S.C. Section 2703(d), 930 F. Supp. 2d 698, 702 (S.D. Tex. 2012) (denying application for order seeking cell-tower dump, “a very broad and invasive search affecting likely hundreds of individuals,” where agents didn’t understand the technology nor discuss what they would do with innocent people’s data). Importantly, the need for disclosure in these contexts does not necessarily turn on the propriety or desirability of permitting or requiring magistrate judges to impose search protocols for digital searches. Compare Orin S. Kerr, Ex Ante Regulation of Computer Search and Seizure, 96 Va. L. Rev. 1241, 1246 (2010) (arguing that magistrates lack constitutional authority to impose ex ante search restrictions), withAdam M. Gershowitz, The Post-Riley Search Warrant: Search Protocols and Particularity in Cell Phone Searches, 69 Vand. L. Rev. 585, 590-591 (2016) (arguing that magistrates should impose ex ante search protocols on cell-phone searches). Even if judges do not impose limits on scope, they must, at the very least, be able to understand what it is they are authorizing the government to do. See, e.g., United States v. Patrick, 842 F.3d 540, 546 (7th Cir. 2016) (Wood, J., dissenting) (expressing concern that courts “know very little about the [Stingray] device, thanks mostly to the government’s refusal to divulge any information about it.”); Zach Lerner, A Warrant to Hack, 18 Yale. J.L. Tech. 26, 44 (2016) (noting that “judges charged with ruling on remote access search warrant applications may not fully understand what they are being asked to authorize”); State v. Andrews, 227 Md. App. 350, 376 (2016) (holding that pen-register-order application which did not disclose intent to use cell-site simulator “failed to provide the necessary information upon which the court could make [] constitutional assessment[]”).

The requirement that policing agencies disclose to courts the techniques used to obtain the information that forms the basis for the requested warrant or court order is less clearly established but nevertheless enjoys some support in existing law. At least one court has in fact held that such notice is constitutionally required. United States v. Moalin, Slip. Op. 3:10-cr-04246-JM-3, at 7 (9th Cir. Sept. 2, 2020). Others have lent support to this principle in a variety of ways. For example, a number of courts have held that evidence obtained as a result of a warrant-based search must be suppressed if the information used to support the warrant application was obtained unlawfully. E.g., United States v. Wanless, 882 F.2d 1459, 1466 (9th Cir. 1989) (“[T]he good faith exception does not apply where a search warrant is issued on the basis of evidence obtained as the result of an illegal search.”). And although some courts have applied the good-faith exception to the exclusionary rule to admit the evidence, these same courts have made clear that the determination depends on the egregiousness of the prior unlawful conduct—which itself requires that the conduct be disclosed to courts. E.g., United States v. O’Neal, 17 F.3d 239, 243 n.6 (8th Cir. 1994) (holding that issuance of a search warrant cannot sanitize “clearly illegal police behavior”). Indeed, several courts have emphasized that the failure to disclose the unlawful conduct to the issuing magistrate at the time of the application counsels strongly in favor of suppression. See, e.g., United States v. Bain, 874 F.3d 1, 21 (1st Cir. 2017) (noting that application of good-faith exception depends “on the accuracy and completeness of the manner in which the information supporting the warrant was conveyed to the magistrate”); United States v. Reilly, 76 F.3d 1271, 1280-1281 (2d Cir. 1996) (holding that “the good faith exception does not apply when officers do not provide an issuing judge with details about their conduct during a pre-warrant search”). In addition, judges have, on a number of occasions, expressed concern that they were misled by police or prosecutors about the manner in which information was obtained. See, e.g., United States v. Patrick, 842 F.3d 540, 546 (7th Cir. 2016) (Wood, J., dissenting) (expressing concern that “the government appear[ed] to have purposefully concealed the Stingray’s use [in executing an arrest warrant] from the issuing magistrate, the district court, defense counsel, and even this court”).

2. Animating concerns. What animates these various cases and statutes is the basic notions that judges cannot fulfill their duty of independent oversight of the information-gathering process if they do not operate in a world of full information—and that individuals who are the targets of information gathering cannot exercise and protect their rights if critical facts are withheld from them. See United States v. Taylor, 935 F.3d 1279, 1303-1304 (11th Cir. 2019) (Tjoflat, J., concurring in part & dissenting in part) (arguing that “[i]t is especially important to demand candor in warrant applications” to ensure integrity in “a process which plays a crucial role in protecting [constitutional] rights”); United States v. Rettig, 589 F.2d 418, 422 (9th Cir. 1978) (finding that officers’ failure “to advise the judge of all the material facts . . . deprived him of the opportunity to exercise meaningful supervision over their conduct and to define the proper limits of the warrant”); see also Stephen W. Smith, Gagged, Sealed, and Delivered: Reforming ECPA’s Secret Docket, 6 Harv. L. & Policy Rev. 601, 620 (2012) (noting that in absence of notification, “law-abiding citizens never charged with a crime are prevented from ever learning of government intrusions into their electronic lives,” which undermines their ability to protect their rights and hampers effective judicial and legislative oversight of these techniques).

To be sure, at times there may be reasons to limit notification to targets or defendants, or to delay it for a period of time. Both federal and state statutes, for example, permit the government—with court approval—to delay notification of wiretaps, orders, and other covert surveillance activities for a period of time when there is reason to believe that notice would put witnesses in danger, lead to the destruction of evidence, or otherwise seriously hamper an ongoing investigation. E.g., USA PATRIOT Act § 213, 18 U.S.C. § 3103a(b) (providing for delayed notice of a warrant or court order if “the court finds reasonable cause to believe that providing immediate notification of the execution of the warrant may have an adverse result” such as flight, destruction of evidence, or harm to witnesses); Wiretap Act, 18 U.S.C. § 2518(8)(d) (providing for notice within 90 days of when wiretap order expires, but allowing for postponement upon “showing of good cause.”). Similarly, courts have recognized that the need to protect the identity of confidential informants may prevail over a defendant’s interest in disclosure—at least in circumstances in which the information is not essential to preparing an adequate defense. E.g., United States v. Napier, 436 F.3d 1133, 1136 (9th Cir. 2006) (balancing defendant’s interest in disclosure against government’s interest in ensuring informant’s safety and upholding denial of motion to unseal); United States v. Cintolo, 818 F.2d 980, 1003 (1st Cir. 1987) (holding that government need not disclose precise location of electronic-surveillance equipment). And of course, for certain kinds of information-gathering activities, such as the use of automated license plate readers (ALPRs)—mandatory notification simply may not be feasible.

3. Regulatory framework. This Section addresses these competing concerns in two ways. First, in the case of criminal defendants, subsection (b) adopts a strong presumption in favor of disclosure of the information-gathering techniques that were used. As courts have pointed out, defendants cannot identify potential problems with the government’s information-gathering activities unless they are apprised at least in general terms about the techniques that are used. See, e.g., United States v. Rose, 2012 WL 1720307 (D. Mass. 2012) (finding that defendant had “met his burden of proof to the extent that some of the requested information” about GPS surveillance device used to track his location “may help him to delineate the scope of a possible Fourth Amendment violation.”); United States v. Hartman, 2015 WL 13864168 (C.D. Cal. 2015) (granting defendant access to certain information about software used to obtain evidence against him). As the Comment explains, however, subsection (b) does not necessarily require that agencies disclose every last detail about the technique at issue; rather, it requires that they provide defendants with enough information to contest the accuracy, validity, and lawfulness of the various techniques that were used. Meanwhile, subsection (c)—which applies to targets who are not eventually prosecuted—urges disclosure primarily in the case of more intrusive information-gathering techniques and permits delayed notification when necessary to preserve the integrity of the investigation.

Disclosure to judges, however, does not raise any of these same concerns. Courts have various mechanisms in place to ensure confidentiality for highly sensitive information. See, e.g., Fed. R. Crim. P. 49.1 (providing for redactions, filings under seal, and protective orders to protect private information). And disclosure to courts would not face the sorts of resource constraints that might preclude mandatory notification to all targets of minimally intrusive information-gathering techniques.

Finally, concern that disclosure—either to defendants or to the courts—will invite greater public scrutiny or regulation of a particular law-enforcement tactic should not be used to justify withholding information. Indeed, the very fact that public awareness of a particular tactic or technique might invite greater regulation is an argument in favor of disclosure, not against it. See generally Hannah Bloch-Wehba, Visible Policing: Technology, Transparency, and Democratic Control, 109 Calif. L. Rev. 917 (2021) (arguing that transparency plays significant role in reforming policing); Barry Friedman & Maria Ponomarenko, Democratic Policing, 90 N.Y.U.L. Rev. 1827 (2015) (same). There have been a number of examples in recent years of agencies concealing the use of various investigative techniques through the use of “parallel construction,” which involves recreating an alternative path to the evidence in order to avoid disclosing how it was originally obtained. See, e.g., Office of the Inspector General, U.S. Dept. of Justice, A Review of the Drug Enforcement Administration’s Use of Administrative Subpoenas to Collect or Exploit Bulk Data (2019) (finding that DEA engaged in parallel construction to conceal bulk-data-collection programs); Kim Zetter, Emails Show Feds Asking Florida Cops to Deceive Judges, Wired (June 19, 2014), https://www.wired.com/2014/06/feds-told-cops-to-deceive-courts-about-stingray/ (reporting that Florida police had routinely told judges in warrant applications that they obtained information from confidential source rather than disclosing use of Stingrays). When these techniques and programs eventually became public, there was considerable public debate about the propriety of their use. See, e.g., Aaron Gregg, FBI Surveillance Devices May Interfere with 911 calls, U.S. Senator Says, Wash. Post (Aug. 24, 2018), https://‌www.‌washingtonpost.com/business/2018/08/24/fbi-surveillance-devices-may-interfere-with-calls-us-senator-says/ (reporting on letter by Sen. Ron Wyden asking DOJ to be more forthcoming on potentially disruptive nature of cell-site simulators); Bipartisan Committee Staff Report: Clear Guidelines Needed For “Stingray” Devices, H. Comm. on Oversight, 114th Cong. (Dec. 19, 2016), https://republicans-oversight.house.gov/report/‌bipartisan-committee-staff-report-clear-guidelines-needed-stingray-devices/ (bipartisan report recommending that Congress pass legislation regulating use of cell-site simulators). The end result was a combination of self-regulation by law enforcement as well as greater legislative and judicial oversight. See, e.g., Adam Lynn, Tacoma Police Change How They Seek Permission to Use Cellphone Tracker, News Tribune (Nov 15, 2014) (reporting that local judges started requiring police to use explicit language to get permission to use cell-site simulators after unwittingly signing orders police said authorized them to use the devices).

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