Commonwealth v. Perry

Decision Date01 April 2022
Docket NumberSJC-13144
Citation489 Mass. 436,184 N.E.3d 745
CourtUnited States State Supreme Judicial Court of Massachusetts Supreme Court

Eric Tennen, Boston, for the defendant.

Cailin M. Campbell, Assistant District Attorney (Jennifer J. Hickman, Assistant District Attorney, also present) for the Commonwealth.

Mason A. Kortz, for Surveillance Technology Oversight Project, amicus curiae, submitted a brief.

Brett Max Kaufman, Ashley Gorski, & Patrick Toomey, of New York, Jennifer Granick, Jennifer Lynch, & Andrew Crocker, of California, Matthew Spurlock, Committee for Public Counsel Services, Matthew R. Segal, Jessie J. Rossman, Jessica J. Lewis, Nathan Freed Wessler, & Joshua M. Daniels, for American Civil Liberties Union & others, amici curiae, submitted a brief.

Present: Budd, C.J., Gaziano, Lowy, Cypher, Kafker, Wendlandt, & Georges, JJ.


As law enforcement capabilities continue to develop in the wake of advancing technology, so too must our constitutional jurisprudence. To this end, we must grapple with the constitutional implications of "tower dumps," a relatively novel law enforcement tool that provides investigators with the cell site location information (CSLI) for all devices that connected to specific cell towers during a particular time frame.

Here, the Commonwealth obtained search warrants for seven tower dumps,1 corresponding to the locations of six robberies and an attempted robbery that resulted in a homicide, all of which investigators believed to have been committed by the same individual. After analyzing the information contained in the tower dumps, investigators determined that the defendant had been near the scenes of two of the crimes. The defendant subsequently was charged with the robberies and the homicide, and he moved to suppress all evidence obtained from the tower dumps as the fruits of an unconstitutional search. A Superior Court judge denied the motion, and the defendant filed an application in the county court seeking leave to pursue an interlocutory appeal; the single justice reserved and reported the case to the full court.

The defendant argues that the Commonwealth's use of the tower dumps intruded upon his reasonable expectation of privacy, and therefore effectuated a search under the Federal and State Constitutions. He also contends that search warrants for tower dumps are per se unconstitutional because they necessarily lack particularity. In addition, the defendant asserts that, here, the warrants were not supported by probable cause.

We agree that the government's use of the seven tower dumps was an intrusion upon the defendant's reasonable expectation of privacy, and therefore constituted a search under art. 14 of the Massachusetts Declaration of Rights. We do not agree, however, that warrants for tower dumps are per se unconstitutional. Accordingly, investigators may use tower dumps so long as they comply with the warrant requirements of art. 14.

Here, the second of the two search warrants was sufficiently particular and supported by probable cause, and therefore the use of the information obtained from it does not offend the Massachusetts Declaration of Rights. The first warrant, however, was not supported by probable cause, and accordingly, any evidence obtained as a result of it must be suppressed.2

1. Background. a. CSLI and tower dumps. An overview of the technology at issue is necessary to a discussion of the issues in this case. Cellular telephones "make calls, send text messages and emails, and access the internet by connecting to a set of radio antennas called ‘cell sites’ " (quotation and citation omitted). United States v. Thorne, 548 F. Supp. 3d 70, 113 (D.D.C. 2021). See Carpenter v. United States, ––– U.S. ––––, 138 S. Ct. 2206, 2211, 201 L.Ed.2d 507 (2018). To receive cellular service, "a cellular telephone will connect to the cell site which provides the strongest signal, typically, albeit not always, the nearest one." Commonwealth v. Jones, 477 Mass. 307, 313 n.11, 77 N.E.3d 278 (2017). "The typical cell site covers a more-or-less circular geographic area," with "three (or sometimes six) separate antennas pointing in different directions" which divide the site's radius into smaller, wedge-shaped sectors. Carpenter, supra at 2225 (Kennedy, J., dissenting).

Once a cellular telephone connects with a cell site (either to send or receive communications), the site will "generate[ ] a time-stamped record known as [CSLI]."3

Id. at 2211. Among other information, this record contains the precise location of the cell site, as well the specific sectors that provided service to the cellular telephone. See Commonwealth v. Augustine, 467 Mass. 230, 237-238, 4 N.E.3d 846 (2014), S.C., 470 Mass. 837, 26 N.E.3d 709 and 472 Mass. 448, 35 N.E.3d 688 (2015) ( Augustine I ). When a cellular telephone establishes a connection with a particular sector of a cell site, it can be inferred that the user was located within that sector's range of service, or "coverage area," at the time of the connection. Commonwealth v. Wilkerson, 486 Mass. 159, 174, 156 N.E.3d 754 (2020). Service providers retain CSLI for their own business purposes, such as finding weak areas of their network, but it also has proved useful to law enforcement in order to approximate an individual's location at a given time. Carpenter, 138 S. Ct. at 2212.

The precision with which police are able to approximate an individual's location varies significantly. Some CSLI only enables investigators to place an individual within "an area miles in diameter," whereas other CSLI allows investigators to "calculate users’ locations with precision that approaches that of GPS.[4 ]" ECPA Reform and the Revolution in Location Based Technologies and Services: Hearing Before the Subcomm. on the Constitution, Civil Rights, and Civil Liberties of the H. Comm. on the Judiciary, 111th Cong., at 23, 25 (2010) (testimony of Professor Matt Blaze) (Blaze Testimony I). The degree of precision largely depends on the size of the sector's coverage area and the technology in use. See id. at 25. The size of the coverage area, in turn, depends on the number of nearby cell sites; "[t]he greater the concentration of cell sites, the smaller the coverage area." Carpenter, 138 S. Ct. at 2211. "As cellular telephone use has grown, cellular service providers have responded by adding new cell sites to accommodate additional customers," resulting in increasingly precise CSLI. See Augustine I, 467 Mass. at 239, 4 N.E.3d 846.

CSLI also is more precise if the cell site uses newer, more advanced technology. In areas such as Boston that use what is referred to as "small cell" technology, CSLI can identify an individual's location precisely, down to the specific floor of a particular building. See State v. Earls, 214 N.J. 564, 578, 70 A.3d 630 (2013), quoting Blaze Testimony I, supra at 25. See also National League of Cities, Small Cell Wireless Technology in Cities, at 8-9 (2018) (discussing Boston's use of small cell technology).5 This technology is becoming increasingly ubiquitous; "[b]y some estimates, the number of these small-scale cellular base stations equaled or outstripped the number of conventional cells in the [United States] in 2010, and their deployment continues to grow at a very fast rate." ECPA, Part 2: Geolocation Privacy and Surveillance: Hearing Before the Subcomm. on Crime, Terrorism, and Homeland Security of the H. Comm. on the Judiciary, 113th Cong., at 55 (2013) (testimony of Professor Matt Blaze).

In conducting a criminal investigation, law enforcement officers may obtain targeted CSLI, which provides a log of every cell site to which an individual cellular telephone has connected within a given time frame, thus enabling investigators retroactively to reconstruct an individual's movements over time. See Augustine I, 467 Mass. at 239, 4 N.E.3d 846. A tower dump, by contrast, provides officers with CSLI from every device that connected to a particular cell site within a specified period; allowing law enforcement to infer that the owners of those devices most likely were present in that site's coverage area during that time. See Carpenter, 138 S. Ct. at 2220 (tower dump is "a download of information on all the devices that connected to a particular cell site during a particular interval"). Tower dumps have proved particularly useful in investigating serial crimes, because they enable investigators to isolate individual devices that were near the scene of multiple offenses. See Owsley, The Fourth Amendment Implications of the Government's Use of Cell Tower Dumps in Its Electronic Surveillance, 16 U. Pa. J. Const. L. 1, 6 (2013).

b. Factual background. On September 22, September 27, September 28, October 4, October 25, and October 31, 2018, clerks at six stores in Boston, Canton, and Cambridge were robbed at gunpoint by an unidentified perpetrator. On October 6, 2018, an unidentified individual shot and killed a store clerk in Boston during an attempted robbery. Almost all of the stores were convenience stores or gasoline stations, and one sold cellular telephones. Because each of the robberies was perpetrated in a comparable manner by a man fitting a similar description, police suspected that the same person had been responsible for all seven incidents. Based on surveillance footage and witness statements, investigators also believed that the perpetrator was at least occasionally assisted by a coventurer who acted as a getaway driver.

Boston police detectives worked together with agents from the Federal Bureau of Investigation (FBI) to identify a suspect. They sought to do so by cross-referencing a series of tower dumps in order to determine if any device had been near the scenes of two or more of the incidents. To this end, on October 26, 2018, an agent with the FBI obtained a search warrant from a Federal magistrate judge, see 18 U.S.C. § 2703, for tower dumps corresponding to the robberies in Boston, Canton,...

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2 books & journal articles
  • Search and seizure of electronic devices
    • United States
    • James Publishing Practical Law Books Suppressing Criminal Evidence Fourth amendment searches and seizures
    • April 1, 2022
    ...does intrude on an individual’s right to privacy and a search warrant is required to obtain this information. Commonwealth v. Perry , 184 N.E.3d 745 (Mass. 2022). Perry involved an investigation of multiple similar armed robbery charges. Two search warrants were issued for cell tower dumps.......
  • Privacy After Carpenter v. United States: Can a Tower Dump Warrant Meet the Warrant Requirement?
    • United States
    • Suffolk University Law Review Vol. 56 No. 1, January 2023
    • January 1, 2023 744 (providing testimony from FBI agent regarding CSLI accuracy). (40.) See supra note 36. (41.) See Commonwealth v. Perry (Perry IT), 184 N.E.3d 745, 753 (Mass. 2022) (explaining "small cell" technology and its increasingly ubiquitous nature). Providers utilize smaller cell sites--known......

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