by Mason Kortz and Christopher Bavitz
In 2014, the Supreme Judicial Court of Massachusetts ruled in Commmonwealth v. Augustine, 467 Mass. 230 (2014) that, under the Massachusetts Declaration of Rights, police must obtain a warrant in order to access cell phone records that can reveal a single person’s location over an extended period of time. Last year, the United States Supreme Court reached the same conclusion under the Fourth Amendment in Carpenter v. United States,138 S. Ct. 2206 (2018). However, neither decision addressed the practice of so-called “tower dumps,” which involve access to a different type of location information–namely, the identity of all cell phones that were in a particular location at a particular time. This article addresses law enforcement use of tower dumps, providing a technical description, an examination of current law, and some thoughts on trends in widescale data collection efforts
Technical Overview: What Are Cell Tower Dumps?
A cellular network is composed of numerous fixed-location cell towers or “cell sites,” each of which covers three or more directional “sectors.” Whenever a cell phone sends or receives data over a cellular network, it connects to one of these cell sites. The network continually tracks which phones are connected to which sites and sectors at any given time. This information — called cell site location information or CSLI — can be logged by the cellular service provider and stored, in some cases for multiple years. Depending on the density of the cellular network in a particular location, CSLI can be used to track a phone’s location with precision varying from a few miles down to a single city block. Newer cellular technologies allow for even greater detail.
The historical CSLI at issue in Augustine and Carpenter could be defined as information on all of the cell sites that a particular device had connected to over a particular interval. The Supreme Court in Carpenter defined a cell tower dump, on the other hand, as “information on all the devices that connected to a particular cell site during a particular interval.” Carpenter, 138 S. Ct. at 2220. The following examples highlight the distinction between the historical CSLI (Scenario A) and tower dumps (Scenario B):
- SCENARIO A — Police are investigating a crime that took place between November 15 and 19, 2018. Officers have probable cause to believe Smith committed the crime. Smith claims to have been nowhere near the scene of that crime, but officers question his alibi based on eyewitness testimony and other evidence. Officers seek a warrant that would require Smith’s cell phone provider to turn over CSLI indicating the location of Smith’s phone between November 15th and 19th.
- SCENARIO B — Police are investigating a crime that took place at 2:00 pm on November 19, 2018 in the 100-block of Main Street. Officers have no indication as to the identity of the perpetrator. Officers seek warrants that require cellular service providers with towers in the area to turn over CSLI for all cell phones that contacted towers near 123 Main Street between 1:50 pm and 2:10 pm on November 19th.
A tower dump, by its nature, involves access to more users’ data than historical CSLI does; indeed, one federal district court has noted that “[a]ny order authorizing a cell tower dump is likely to affect at least hundreds of individuals’ privacy interests.” In the Matters of the Search of Cellular Telephone Towers, 945 F. Supp. 2d 769, 770 (S.D. Tex. 2013). That said, a typical tower dump is confined in the sense that it covers both a small area and a relatively short time period — often a few hours or even a few minutes. Thus, a tower dump reveals less about any given individual’s movements over a period of time than does historical CSLI.
Current State of the Law
The primary legal question concerning cell tower dumps is whether they require a warrant or, alternatively, can be obtained under the Stored Communications Act (“SCA”), 18 U.S.C. § 2703(d). If the warrant requirement applies, the government would need to show probable cause in order to obtain a tower dump. Section 2703(d) of the SCA, on the other hand, requires only “specific and articulable facts showing that there are reasonable grounds to believe that the contents of [the cell tower dump] are relevant and material to an ongoing criminal investigation.”
Proponents of the warrant requirement argue that individuals have a reasonable expectation of privacy in their location information and that cell tower dumps therefore fall within the ambit of the Fourth Amendment. Alternatively, they argue that even if cell tower dumps do not infringe on any one person’s privacy, the sheer number of data points collected with each dump constitute “dragnet surveillance,” which the Supreme Court has suggested may be unlawful.
The majority of courts to consider the question have rejected these arguments and held that a warrant is not required to obtain a cell tower dump. Many of these decisions rely on the third-party doctrine, which provides that an individual has no legitimate privacy interest — and, therefore, no Fourth Amendment protection — in information that he/she voluntarily discloses to a third party (in this case, that person’s cell phone service provider). Such courts have also noted that, although cell tower dumps collect information about a large number of subscribers, they often cover relatively limited time periods.
On the other hand, at least one United States Magistrate Judge has held that cell tower dumps implicate the Fourth Amendment and therefore require a warrant. See In re United States ex rel. Order Pursuant to 18 U.S.C. Section 2703(d), 930 F. Supp. 2d 698 (S.D. Tex. 2012) (denying § 2703(d) application to obtain tower dump, holding that warrant is required). The court expressly relied on an order extending Fourth Amendment protections to historical CSLI, a decision later reversed by the Fifth Circuit. By its nature, a cell tower dump includes information that turns out not to be relevant to the investigation in question, and the Magistrate Judge was concerned that the government had made no plans for how to handle or dispose of that information. Thus, the court declined to approve an application for a cell tower dump until both (a) it was supported by probable cause; and (b) the government presented a protocol for minimizing the intrusion into the privacy of technological bystanders.
Looking Ahead: Developments Post-Carpenter
Although the Court in Carpenter did not reach the question of cell tower dumps, its decision will certainly have an impact on this evolving body of law. In holding that a warrant is not required to obtain cell tower dumps, many lower courts have expressly relied on appellate decisions permitting warrantless access to historical CSLI. Carpenter has now abrogated those decisions. Historical CSLI and tower dumps raise different privacy concerns, though, so lower courts applying Carpenter and Augustine to tower dumps will still need to engage in an independent analysis of whether the information the government seeks would invade individuals’ reasonable expectations of privacy.
Carpenter set forth two important holdings. First, it limited the application of the third-party doctrine to historical CSLI on the grounds that the pervasiveness of cell phones (and the essentially invisible way in which they generate location information) rendered any disclosure of CLSI effectively non-voluntary. The application of this holding to tower dumps should be straightforward: because tower dump CSLI and historical CSLI are generated in the same fashion, it stands to reason that the third-party doctrine does not apply to either one.
Second, Carpenter made clear that the collection of seven days of historical CSLI infringes on a cell phone user’s reasonable expectation of privacy and, absent exceptional circumstances, requires a warrant. The application of this holding to cell tower dumps is less certain. While tower dumps implicate the privacy of far more people than access to historical CSLI does, they are arguably less invasive at the individual level. The Court in Carpenter declined to state whether there is some lower limit to the collection of CSLI below which a warrant is not required. The SJC in Augustine did reach this question, setting the limit at six hours of CSLI. However, the SJC was presumably thinking of six hours CSLI for a single person–not six hours of CSLI for everyone whose cell phone passed by a specific location in that time period. Thus, the analogy between historical CSLI and tower dump CSLI is imperfect.
Finally, because the Court in Carpenter did not address tower dumps, it did not reach the question of what to do with hundreds, perhaps thousands, of innocent bystanders’ location information. Regardless of whether the warrant requirement applies, future courts that address the question of cell tower dumps will need to consider how to craft — or ensure that government entities requesting CSLI craft — mechanisms to minimize potential privacy harms caused by these broad and far-ranging requests.
Warrantless tower dumps, widely approved up until recently, are now on uncertain footing. Tower dumps that cover more than a few hours without a warrant are questionable under Carpenter and almost certainly unlawful in Massachusetts under Augustine. Even narrower tower dumps raise questions due to the number of people affected, although courts may focus more on minimizing harm through search protocols than on the warrant requirement. Courts and practitioners should also keep in mind that, as both the Supreme Court and the SJC observed, the granularity and precision of CSLI continues to increase dramatically as new network technologies are rolled out. The arguments that prevailed in Carpenter and Augustine are likely to become even more compelling as the relevant technologies continue to evolve.
Mason Kortz is a Clinical Instructor at the Harvard Law School Cyberlaw Clinic, part of the Berkman Klein Center for Internet & Society. His areas of practice include electronic search and seizure, online speech and privacy, open records and government transparency, and the law of artificial intelligence.
Christopher Bavitz is the WilmerHale Clinical Professor of Law at Harvard Law School, Managing Director of the Law School’s Cyberlaw Clinic, and a faculty co-director of the Berkman Klein Center for Internet & Society.
by John T. Mulcahy
The Supreme Judicial Court (the “SJC”) recently ruled in two factually similar cases that police can conduct a warrantless cell phone search pursuant to the “search incident to arrest” exception to the warrant requirement. The SJC’s holdings leave open many questions and evolving cell phone technology will create challenges for courts as they grapple with such searches under the Fourth Amendment. This article analyzes those two cases and considers their implications and some larger questions.
In Commonwealth v. Phifer, 463 Mass. 790 (2012) and Commonwealth v. Berry, 463 Mass. 800 (2012), the SJC ruled as a matter of first impression that the police can search a cell phone incident to arrest. The Court noted that its holding in both cases was narrow. In Phifer, the defendant moved to suppress a warrantless search of his cell phone after he had been arrested and transported to the police station. The defendant had been arrested on two outstanding warrants related to drug charges. The detective checked the call history on the phone and discovered the phone number of a person whom the police knew to be a drug user. The defendant moved to suppress; the trial court denied the motion, citing federal circuit and district court decisions holding that a cell phone can be searched incident to arrest.
The SJC ruled that the detective’s review of the defendant’s recent call history was a proper search incident to arrest. The Court relied heavily on Commonwealth v. Madera, 402 Mass. 156, 159-161 (1998) in reaching its decision. In Madera, the Court upheld the search of a gym bag incident to arrest where the police had probable cause to believe that bag contained evidence of the crime charged. The Court ruled that, as in Madera, the police in Phifer had probable cause to believe that a search of the cell phone would turn up evidence of the crime at issue. Before the defendant’s arrest in Phifer, police saw the defendant on his cell phone and saw him with someone who was a known drug user. Also, the detective had testified that drug dealers use cell phones as part of the drug trade.
The Court also ruled that even though this search was conducted at the time of booking, not arrest, it was still justified as a search incident to arrest; the delay in the search was of no importance because the cell phone found during booking had to have been on the defendant’s person at the time of arrest.
The Court cautioned that its holding should be read narrowly, and that its decision would not “necessarily . . . be the same on different facts, or in relation to a different type of intrusion into a more complex cellular telephone or other information storage device.”
On the same date as the Phifer case, the SJC also issued its decision in Berry. In that case, the police saw the defendant sell heroin. After the defendant was arrested and brought back to the police station, the police officer looked at the recent call history on the defendant’s cell phone and dialed the most recent phone number, which called the heroin customer. Consistent with Phifer, in Berry, the Court stated that a search of a cell phone does not have to be contemporaneous with arrest, but that it can occur during booking at the police station. The SJC held that the search was proper because it was a “very limited search” and the police had reason to search based on their experience that cell phones are used in drug transactions. The SJC again cautioned that it would not necessarily come to the same conclusion if it were dealing with different facts.
In explicitly noting the limitations of its holdings in Berry and Phifer, the SJC recognizes that the law on cell phone searches is still developing. These cases make clear that court review of cell phone searches will be a fact-specific exercise; at least for the near term, courts will not be able to establish a bright-line rule for analyzing these scenarios. The different factual scenarios and ever-changing capabilities of cell phones make the formulation of such a rule difficult. As Justice Gants’ concurring opinion in Phifer points out, the SJC’s comparison of cell phone searches to the search of a gym bag in Commonwealth v. Madera might have over-simplified the analysis. A gym bag is a bounded object, while the information that can be accessed through a cell phone is potentially limitless. Phifer and Berry dealt only with call history, but the average smartphone also has a camera, a calendar, maps, contacts, email, text messages, and can even contain a user’s flight information and purchase information. It is obvious that this kind of information would be of great interest to law enforcement officials. Flight information and maps could quickly show a police officer the recent whereabouts of a suspect, while purchase information could reveal additional evidence.
Another example of technology’s unrestricted potential is Apple’s iCloud service. ICloud is a storage system that allows a user to access his or her music, email, contacts, and word-processing documents on several different devices. Information on the iCloud system exists on Apple’s computer servers outside the jurisdiction of the Commonwealth’s courts. Will police be able to seize a cell phone and access information that exists across multiple jurisdictions through iCloud?
A common criticism of warrantless searches of cell phones is that police can wait to obtain a warrant. The argument goes that a cell phone is different from an automobile, whose mobility means that evidence can be lost quickly. Automobiles therefore are the proper subject for warrantless searches while cell phones are not; an officer, in possession of a cell phone, can put it away and all of the incriminating material on it is safe until he obtains a warrant. But that argument ignores the current technology. As Courts have already warned, the data on cell phones can be destroyed remotely. United States v. Valdez, 2008 WL 360548, *3 (E.D. Wis. Feb. 8, 2008); United States v. Dinwiddie, 2008 WL 4922000, *12 (E.D. Mo. Jan. 29, 2008).
Thus, by the time a police officer obtains a search warrant, even though the cell phone has been safely stored in an evidence locker, the incriminating evidence on that phone could be gone. Law-enforcement officials caution that this scenario could present significant problems in fighting crime.
Perhaps acknowledging that time can be of the essence in these searches, some courts rely on the exigent circumstances exception to the warrant requirement, rather than the search incident to arrest exception. United States v. Lottie, 2008 WL 150046, *3 (N.D. Ind. Jan. 14, 2008); United States v. Parada, 289 F. Supp. 2d 1291, 1303 (D. Kan. 2003). Indeed, in contrast to the SJC, other courts have disapproved of searches that are “incident to arrest” but separate in time from the arrest. See, e.g., United States v. Gibson, 2012 WL 1123146, *10 (N.D. Cal. Apr. 3, 2012); see also, United States v. Valdez, 2008 WL 360548, *3 (E.D. Wis. Feb. 8, 2008); State v. Isaac, 2009 WL 1858754, *5 (Kan.Ct. App. June 26, 2009).
The search incident to arrest doctrine raises concerns of its own. While the Phifer and Berry courts suggested that a search conducted at booking is still a search incident to arrest, other courts have interpreted the exception literally – any search later in time from the actual arrest is not a search incident to arrest. Practically speaking, police officers will not be able to search much of a cell phone at the exact time of arrest. Depending on how the search incident to arrest exception is applied going forward, a police officer might be able to get through only a small part of a suspect’s address book or recent call history before the arrest is completed. Then, police would presumably be required to obtain a search warrant for the rest of the cell phone. Police would then have to contend with the reality that they may not yet have seen the most damning evidence and that this relevant evidence could be destroyed remotely.
In fact, the developing law leaves undefined the limits on the scope of a search of cell phones incident to arrest. Should police officers be able to search any phone the defendant possesses for information or files related to the crimes that they are investigating? Or should police only be allowed to search a phone that is, itself, connected to the crime being investigated? One court has answered the second question affirmatively, finding that police were not warranted in searching a cell phone while arresting an individual for public intoxication and neglect because the phone could not be tied to those particular crimes. Kirk v. State, 974 N.E.2d 1059, 1071 (Ind. Ct. App. 2012).
One thing the cases make clear is that the law is not developing at a rate that keeps pace with technology. As the cases above indicate, courts disagree about how long a search may take place after arrest and still be “incident to arrest,” and there has been little consideration of how closely such a search must be tied to the crime being investigated. Ruling that the search is required by exigent circumstances also has its pitfalls – most obviously, the argument that, once seized and secured, a cell phone may properly by searched pursuant to a warrant. A Supreme Court concurrence offers one potential avenue for lawyers to explore in trying to explain the need for cell phone searches at the time of arrest. In the 2004 case of Thornton v. United States, 541 U.S. 615, 629-30 (2004), Justice Antonin Scalia, joined by Justice Ruth Bader Ginsburg, argued in a concurring opinion that, instead of its traditional justifications, search incident to arrest could be understood as an “evidence-gathering” tool used to compile, at the time of arrest, any evidence related to the crime charged. This conception of search incident to arrest could better be suited to the search of cell phones given the uncertainty over whether data on a cell phone can be or will be destroyed remotely.
As the SJC recognized in both Phifer and Berry, the law on cell phone searches is in its infancy. This body of law will likely force a significant development in Fourth Amendment jurisprudence. No longer is it the search of a glove box or a gym bag. Indeed, the rapid pace of innovation appears to prevent the establishment of any clear guiding principles for cell phone searches. Courts must carefully assess how traditional search and seizure principles should be applied to cell phones and how those principles could be altered to reach a common-sense approach that is constitutionally sound. The Legislature would be wise to consider these same questions in order to provide much-needed guidance to courts, and practitioners would be well advised to educate courts about the relevant technology where a cell phone search is at issue.