§ 2.02. Information Gathering

For the purposes of these Principles, “information gathering” is any governmental action designed to acquire evidence of, or to deter, prohibited conduct that involves:

  • (a) taking action that constitutes a “search” within the meaning of the Fourth Amendment;
  • (b) using technology that enhances the natural senses to detect or to record information;
  • (c) obtaining personally identifiable information or records from a nongovernmental entity through purchase or compulsory process;
  • (d) accessing a database controlled by another government agency to obtain personally identifiable information;
  • (e) using an undercover agent or informant to obtain information; or
  • (f) engaging in behavior that would be unlawful if carried out by a member of the public.


a. Information gathering, generally. In order to maintain public safety and enforce the law, governmental agencies—primarily but not exclusively policing agencies—must gather information. Some of the means of doing so, like entering a home or reading private communications, are extremely intrusive. Others, such as recording a number on a license plate, observing who is entering a given address, or using closed-circuit television (CCTV) cameras in a public space, may be somewhat less so. Whatever the level of intrusion, however, activities like these ought to be regulated, to a greater or lesser degree. The tendency has been to look to the Fourth Amendment, which refers to “searches and seizures,” as a primary regulator of such conduct—although of course there are state constitutions, various relevant statutes, and the policies of individual agencies as well.

If the goal is to ensure sound regulation of various policing practices, the Fourth Amendment is a poor fit. That is because the Fourth Amendment covers a much smaller range of governmental activity than that which calls for regulation, and because the Fourth Amendment offers a relatively blunt and narrow set of regulatory tools. The two points are related.

First, the constitutional framework excludes a wide range of governmental information-gathering activities that call out for some regulation, even if not through the “warrant and probable cause” regime enforced by the courts. Among them is the acquisition of data from third parties, as well as the use of various surveillance technologies, such as license-plate readers and drone surveillance. Although these activities fall short of a Fourth Amendment “search,” they nevertheless can be used to gather a great deal of information about individuals’ whereabouts and day-to-day habits. If left entirely unregulated, they have the potential to be overused, or to be deployed in arbitrary or discriminatory ways. For this reason, many law-enforcement agencies have policies in place to regulate the use of technologies and tactics that fall outside the definition of a Fourth Amendment search. And as discussed in greater detail in § 2.05, both the federal government and the states have adopted comprehensive statutes to regulate the use of some of these technologies.

Second, regulating these information-gathering techniques by way of constitutional law may be both over- and under-protective of the interests at stake. The traditional tools of Fourth Amendment regulation are individualized suspicion (either reasonable suspicion or probable cause) and judicial process (either by obtaining a warrant in advance of action or judicial review afterward, or both). Many of the information-gathering activities discussed here, however, are used early in the course of an investigation—well before police officials could meet the requirements of either reasonable suspicion or probable cause. Requiring officials to satisfy the Fourth Amendment’s suspicion thresholds could significantly hamper investigative efforts or lead courts to significantly lower the standards to accommodate law-enforcement needs. At the same time, many of these information-gathering techniques are used in contexts that may never trigger ex post judicial review but still may be used in ways that raise a host of concerns about the legitimacy of government conduct, be they intrusions on privacy or chilling of First Amendment activity, questions of disparate impact on various populations, or even something as mundane yet essential as weakening data security. Unlike courts, which must rely on the constitutional blunderbuss, agencies and legislatures can operate with a scalpel. Moreover, they have a much broader set of tools at their disposal—from training and supervisory approval, to auditing and public reporting—all of which can be used to reach the broader set of concerns. Even when it comes to the issue of “cause,” legislatures and agencies can utilize a broader range of possible predicates, ranging from the baseline requirement of a legitimate law-enforcement purpose to a showing that exceeds the constitutional requirements of probable cause.

The goal of these Principles is to provide concrete guidance to both legislatures and agencies in crafting an appropriate set of protections to regulate the various investigative activities in which police officials may engage, regardless of whether they fall within the scope of the Fourth Amendment. To that end, the Principles in the Chapters that follow apply not only to traditional searches and seizures, but to “information gathering”—a category of activities that necessarily is broader than that set out in the U.S. Constitution. At the same time, because the Principles are aimed at legislatures and agencies as opposed to courts, the regulatory consequences of deeming something “information gathering” can be more tailored to address both the needs of law enforcement and the unique concerns that various policing tools pose. The Principles in the Chapters that follow draw on a broad array of regulatory measures to ensure that the various tactics not addressed by constitutional regulation are used in a sound manner.

b. Investigating or deterring prohibited conduct. An important limitation on the definition of “information gathering” is that it only covers activities designed to uncover evidence of, or to deter, prohibited conduct. Government agencies routinely gather information for other purposes as well, i.e., to administer government programs, enroll children in schools, grant licenses, and the like. These activities would not be considered “information gathering” subject to the requirements of Chapters 3 and 5.

On the other hand, the definition would apply to more traditional administrative agencies when they gather information in order to identify potential violations of laws or rules. For example, when social-welfare agencies compel beneficiaries to submit to drug testing, or when government officials inspect factories or workplaces for health-and-safety violations, they must do so in compliance with the Principles set forth in the following Chapters. Similarly, these Principles would apply when agencies gather information to uncover violations of their own rules. School officials, for example, may search a student’s purse or locker to enforce school discipline. Agency supervisors may review an employee’s e-mails, or look through an employee’s desk, in order to monitor compliance with workplace rules. These activities raise many of the same concerns regarding intrusiveness, arbitrariness, and the potential for discrimination discussed throughout these Principles. For this reason, agencies should conduct these activities in a manner that is, to the extent feasible, consistent with the Principles set forth in the Chapters that follow.

c. Technologically enhanced surveillance. Observation is an inherent part of law enforcement. Officers routinely are on the lookout for suspicious activity that warrants further investigation, and these activities are typically not regulated in any way. As the U.S. Supreme Court increasingly is beginning to recognize, however, technology transforms the nature of observation in ways that require supervision, even when it is deployed in public spaces in which individuals typically do not have an expectation of privacy. For example, tailing an individual over a period of days would be extremely difficult and require a team of officers, whereas GPS devices can be used to easily track multiple suspects for months at a time. A CCTV camera similarly is fundamentally different from an officer standing on a corner: it is considerably cheaper to deploy, it is more difficult for members of the public to detect, and it can capture images or video that may be stored for years. An officer can observe the license plate of the car in front of him and check for outstanding warrants; an automated license-plate reader (ALPR) can scan thousands of plates in any given day and record the precise location of each plate it sees. Tools such as CCTVs and ALPRs can save valuable law-enforcement resources and make policing agencies considerably more effective, but they also have the potential to be considerably more invasive. It therefore is essential that high-level agency officials—and the broader public—take responsibility for how technologically enhanced observation is used by adopting the sorts of policies described in Chapters 3 and 5.

d. Accessing or acquiring personally identifiable information from third-party record-holders. Government agencies, especially law-enforcement agencies, routinely acquire data and documents from third parties such as banks, cellular-phone companies, and commercial vendors. Sometimes third parties turn over such data or records of their own volition in response to a specific police request. These requests are governed by § 2.05. In many instances, however, government officials compel the production of information, either through a court order or through a subpoena issued by a grand jury, a prosecutor, or by the government agency itself. Government officials also acquire data through purchase, including call records, credit-card information, purchasing history, payroll records, location data from license-plate readers or cellular phones, and social-media use. The information contained in third-party databases is an important resource for policing agencies and can provide crucial leads, particularly in the early stages of a criminal investigation. At the same time, agency access to such information—particularly when used to investigate unlawful conduct—raises a variety of concerns, from its potential to chill lawful activity to the possibility that the information will be abused or used to disproportionately target marginalized groups.

Under the U.S. Supreme Court’s “third-party-doctrine”, if a person voluntarily shares information with a third party, such as a phone company or a bank, the government may access the third party’s records without obtaining a warrant because doing so would not constitute a Fourth Amendment search. For the purposes of these Principles, however, any acquisition of data or information through purchase or compulsory process is considered “information gathering,” unless the records are “de-identified,” meaning they cannot be linked to a particular individual. As discussed above, and in the Chapters that follow, this does not mean that anytime the government wishes to acquire information it must first obtain a warrant supported by probable cause. Rather, it means that the acquisition must take place according to the Principles for either suspicion-based or suspicionless policing set out in Chapters 3 and 5.

e. Accessing government databases. In addition to obtaining information and records from nongovernmental third parties, agencies also gather information by accessing data that other government agencies have collected. Local policing agencies pull criminal records from state and federal law-enforcement databases, access driving records from motor-vehicle-agency databases, and at times draw on personal information collected by other administrative and social-welfare agencies. Because these data already are in government hands, accessing these records typically would not be considered a “search” for Fourth Amendment purposes. At the same time, few would argue that every government official should have unfettered access to every single record that government agencies collect. Both legislatures and agencies themselves have recognized the importance of imposing limits on agency access to various databases to ensure that the information is used properly, and to minimize the privacy concerns that arise when information about individuals is aggregated across multiple databases and policy domains. Thus, agency acquisition of information from other government agencies also is “information gathering” governed by the Principles set forth in Chapters 3 and 5. For the same reasons, even law-enforcement access to its own databases requires some restrictions, as are set out in Chapter 6.

f. Use of undercover agents and informants. Policing agencies also at times rely on undercover agents and informants in order to obtain information about unlawful conduct that would not otherwise come to light. Informants play a particularly vital role in investigations of criminal conspiracies, as well as certain forms of public corruption, which are difficult to pursue in the absence of inside information. However, the use of informants can be highly intrusive and can potentially impede the right to free association by engendering suspicion within groups that their activities are being surreptitiously monitored by the state. Under the U.S. Supreme Court’s “reasonable expectation of privacy” framework, the use of informants and agents does not amount to a Fourth Amendment search on the theory that when individuals interact with others, they “assume the risk” that any information they share may be passed along to the government. But this does not mean that the use of informants and agents should not be carefully regulated—as is evident by the many agencies at the local, state, and federal level that have adopted policies to carefully circumscribe their use.

These Principles address the use of informants in two ways. First, they make clear that whenever officials affirmatively use either undercover agents or informants to obtain nonpublic information (as opposed to passively accepting information from informants or witnesses), they are engaging in “information gathering” and should ensure that they do so in accordance with the Principles set forth in Chapters 3 and 5. Second, these Principles also deal separately in Chapter 12 with the broader range of concerns that are implicated by the use of informants, including informant safety and the reliability of their testimony, that go beyond the scope of the information-gathering principles in the Chapters that follow. These two sets of Principles are intended to work in tandem. Chapter 12 provides agencies with more specific guidance on how to operationalize the various safeguards described in Chapters 3 and 5. But it also outlines a variety of additional measures that agencies may need to take to address concerns that are unique to informants.

g. State and local positive law. Although government officials sometimes are exempt from prohibitions that apply to the general public, when officials engage in activities that would be unlawful if carried out by a member of the public they should take particular care to ensure that they exercise their authority in responsible ways. Although courts, in interpreting the Fourth Amendment, traditionally have resisted looking to positive law to define the scope of its protections, there are signs in recent U.S. Supreme Court decisions that this approach may be changing, and for good reason: positive law is a particularly apt source of guidance for agencies and legislatures in distinguishing between those activities that may be left entirely to officer discretion and those that ought to have some degree of agency supervision. For example, most states have laws that prohibit trespassing onto private property, going through someone’s trash, or releasing certain kinds of data without the user’s permission. These laws are an important indication of societal expectations and suggest that the activity in question is sufficiently intrusive that agencies at the very least should provide guidance to officers and other officials about the manner in which the activity should be used. See Chapters 3 and 5.

h. Line-drawing difficulties and the need to err in favor of complying with Chapters 3 and 5. The five categories of information-gathering activities described here are intended to provide guidance to agencies and legislatures in identifying the sorts of tactics that ought to be subject to regulation. The list is not exhaustive, nor—as courts and commentators have discovered—is line-drawing easy. Inevitably, there will be activities that arguably do not fall within the definition of “information gathering” but raise a similar set of concerns. To take an easy case, an officer who is watching passersby while patrolling public streets unavoidably is “gathering information,” but that simple act does not fall within these Principles, nor should it. On the other hand, if an officer uses a camera to document evidence at a crime scene, such conduct arguably falls within the definition of “information gathering,” but it is not clear it requires regulatory guidance along the lines prescribed in Chapters 3 and 5, as opposed to the Principles on evidence-gathering set forth in Chapter 8. Aerial surveillance from a helicopter sometimes may be conducted by a government official without the benefit of any technological enhancement, and depending on the height at which the helicopter is flown, could fall outside the positive-law limitation in subsection (e). At the same time, aerial surveillance of any sort raises a variety of concerns, including privacy, safety, and noise; and it is precisely the sort of activity that an agency may wish to regulate at least to some degree. Although line-drawing can be difficult, when in doubt, agencies should err in favor of adhering to the Principles set out in Chapters 3 through 5, and, in particular, in having a policy in place to provide guidance to low-level officials in deciding when and how a specific technique ought to be used. Regulatory guidance should become the norm for police information-gathering.

Reporters’ notes

The question of whether a practice ought to be regulated differs in important ways from the question of whether something ought to be deemed a search for Fourth Amendment purposes. In deciding whether to regulate, legislatures and agencies are not bound—as are courts—by the text of the Fourth Amendment, its history, or the various principles of constitutional interpretation that have informed the U.S. Supreme Court’s jurisprudence. See United States v. Jones, 565 U.S. 400, 410-411 (2012) (relying on text of Fourth Amendment to explain why “open fields” are not protected); Payton v. New York, 445 U.S. 573, 583-585 (1980) (relying on history of Fourth Amendment to explain why statute authorizing police officers to enter a residence without a warrant to make a felony arrest is unconstitutional); see also Orin S. Kerr, The Effect of Legislation on Fourth Amendment Protection, 115 Mich. L. Rev. 1117, 1159 (2017) (“The possibility of statutory privacy offers several substantial advantages over the Fourth Amendment alone. Legislatures are not bound by text, history, or precedent.”). And they are not limited to the fairly blunt set of tools that courts have at their disposal to implement the Fourth Amendment’s commands. Orin S. Kerr, The Case for the Third Party Doctrine, 107 Mich. L. Rev. 561, 597 (2009) (pointing out that legislation often can “strike a middle ground not possible under the Fourth Amendment.”). Regulation does not mean prohibition, and, importantly, it does not mean that a particular tactic can only be deployed if police officials satisfy the requirements of reasonable suspicion or probable cause. What it means is that democratically accountable legislators—or at the very least, high-level officials within an agency—have taken responsibility for how the tactic is deployed. Barry Friedman & Maria Ponomarenko, Democratic Policing, 90 N.Y.U. L. Rev. 1827, 1832 (2015).

In deciding whether to regulate, then, the question is whether a particular investigative strategy implicates a set of values that ought not be balanced anew by each individual officer in the field. Framed that way, the justification for including each of the categories above under the definition of “information gathering” becomes readily apparent. Consider, for example, the last item on the list: “behavior that would be unlawful if carried out by a member of the public.” The U.S. Supreme Court has held that positive law is not determinative of Fourth Amendment rights, and, as a result, officers who trespass on private property or dig through people’s trash, in violation of state or local ordinances, are not necessarily conducting a “search” within the meaning of the Fourth Amendment. Oliver v. United States, 466 U.S. 170, 183-184 (1984) (noting that the law of trespass is not dispositive of whether an intrusion on land violates the Fourth Amendment); California v. Greenwood, 486 U.S. 35, 40-41 (1988) (holding that looking through trash is not a “search”); but see Providence, Rhode Island Code of Ordinances § 12-87 (prohibiting any person from “scaveng[ing] household rubbish, garbage or recyclables”). But surely it does not follow that individual officers ought to decide for themselves which broadly applicable statutes they ought to comply with—and which they should feel free to ignore.

Indeed, all of the investigative activities listed here are ones that many agencies and legislatures have subjected to some degree of regulation. Thus, a number of states have adopted statutes to regulate the use of various technologies such as drones, license-plate readers, and facial-recognition software. See, e.g., Vt. Stat. Ann. tit. 20, § 4622(a) (prohibiting law-enforcement agencies from using a drone to “investigat[e], detect[], or prosecut[e] crime”); Md. Public Safety Code Ann. § 3-509(b) (limiting law enforcement use of automated captured plate data to “legitimate” purposes); Oakland, Cal. Mun. Code § 9.64.045(A) (forbidding the city of Oakland from “obtain[ing], retain[ing], request[ing], access[ing], or us[ing] face recognition technology.”). And many departments have adopted policies to regulate still other technologies. Los Angeles Police Department Manual 568.55, L.A. Police Dep’t, http://www.lapdonline.org/lapd_manual/ (last visited June 23, 2020) (requiring a warrant, unless in the case of an emergency, for use of cellular-communications-interception technology); Operations Order 3.27(8), Phx. Police Dep’t, https://www.phoenix.gov/policesite/Documents/operations_orders.pdf (last visited June 23, 2020) (requiring supervisor approval for use of social media by investigators). Both the federal government and the states regulate law-enforcement access to various third-party databases—from medical records to video-store-rental histories. See Erin Murphy, The Politics of Privacy in the Criminal Justice System: Information Disclosure, the Fourth Amendment, and Statutory Law Enforcement Exemptions, 111 Mich. L. Rev. 485, 546 (2013) (listing major federal privacy statutes); see, e.g., Video Privacy Protection Act, 18 U.S.C. § 2710, et seq. (protecting information held by “video tape service providers”); Internal Revenue Code (Tax Reform Act of 1976), 26 U.S.C. § 6103 (protecting tax information); Family Educational Rights and Privacy Act, 34 C.F.R. § 99.31(a)(9)(i) (protecting personal information held by educational institutions); Bank Records Act, 12 U.S.C. § 1952 (protecting bank records). They also regulate how information may be shared among government agencies. See, e.g., 13 U.S.C. § 9 (limiting inter-agency access to census data); 5 U.S.C. § 522a (regulating inter-agency sharing of personally identifiable information). Both agencies and legislatures have imposed various restrictions on the use of informants. See, e.g., Fla. Stat. § 914.28(5)(a)–(h) (listing various factors a law enforcement agency should factor in “assess[ing] the suitability of using a person as a confidential informant”); Los Angeles Police Department Manual 544.30, L.A. Police Dep’t, http://www.lapdonline.org/‌lapd_manual/ (last visited June 23, 2020) (requiring officers to keep supervisors informed “of their relations and activities involving informants”).

Yet, as is often the case given that there are 50 states and some 18,000 law-enforcement agencies, there are many notable gaps. John Rappaport, Second-Order Regulation of Law Enforcement, 103 Calif. L. Rev. 205, 214 (2015) (highlighting that 84 percent of law-enforcement agencies have no lineup procedures in place); Samuel Walker, The New Paradigm of Police Accountability: The U.S. Justice Department “Pattern or Practice” Suits in Context, 22 St. Louis U. Pub. L. Rev. 3, 17 (2003) (noting that “the use of informants, other undercover tactics, deployment of the canine unit, etc.” remain unregulated). The goal of the Principles that follow is to provide an overarching framework to guide policymakers in providing guidance to officers and agencies where it is presently lacking.

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