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Massachusetts Supreme Judicial Court Announces New Rule Governing Warrants for CSLI and Tower Dumps, Suppresses CSLI Evidence Because Warrant Lacked Particularized Facts Establishing Nexus Between Defendant’s Use of Cell Phone and Charged Crimes

by Anthony W. Accurso

The Supreme Judicial Court (“SJC”) of Massachusetts validated one warrant for cell site location information (“CSLI”) while finding a second deficient for failure to establish probable cause, and it issued prospective guidelines for CSLI warrants going forward.

Seven businesses around the Boston area were subject to armed robberies between September 22 and October 31 of 2018. During one robbery on October 6, the store clerk was shot and killed.

After collecting statements from witnesses, investigators with the Boston Police Department (“Boston PD”) and the FBI believed that one individual was responsible for these robberies, and the suspect likely had the same getaway driver for several of the robberies. However, because they lacked any identifying information on the suspects, police sought CSLI data collected from nearby cell towers for the purpose of cross-referencing the data from each tower to determine if any cell phones were in the vicinity of all or several of the robberies at the time they occurred.

Through two warrants, investigators obtained information on “over 50,000 unique telephone numbers.” After cross-referencing the data, they determined a phone belonging to Jerron Perry was nearby the robberies on October 6 and October 30 and located a phone it contacted regularly (likely the getaway driver) that was nearby the robberies on September 22, October 6, and October 31. Perry was eventually linked to six of the incidents and charged with several counts, including unlawful possession of a firearm, masked armed robbery, and murder in the first degree.

Perry filed a motion challenging the validity of the warrants. After determining he had standing to challenge them, the superior court judge found the warrants were sufficiently particular, and limited in scope, so Perry’s motion was denied.

Perry sought, and was granted, leave to file an interlocutory appeal challenging the denial of his motion.

The SJC reviews searches and seizures for validity under the Fourth Amendment to the U.S. Constitution and Article 14 of the Commonwealth’s Constitution. See Commonwealth v. Feliz, 159 N.E.3d 661 (Mass. 2020). A search for constitutional purposes occurs “when the government’s conduct intrudes on a person’s reasonable expectation of privacy.” Commonwealth v. Augustine, 4 N.E.3d 846 (Mass. 2014) (and subsequent appellate history). A person has a legitimate expectation of privacy where “(i) the individual has manifested a subjective expectation of privacy in the object of the search, and (ii) society is willing to recognize that expectation as reasonable.” Augustine (paraphrasing Katz v. United States, 389 U.S. 347 (1967)). The Court cautioned that when analyzing the expectation of privacy issue under the state Constitution, “we do not necessarily reach the same result as under Fourth Amendment analysis.” Commonwealth v. Panetti, 547 N.E.2d 46 (Mass. 1989).

The Court instructed that when considering searches in the context of technological surveillance, the SJC is careful to “assure[] preservation of that degree of privacy against government that existed when the Fourth Amendment was adopted.” United States v. Carpenter, 138 S. Ct. 2206 (2018) (quoting Kyllo v. United States, 533 U.S. 27 (2001)).

To undertake the difficult task of analyzing police use of technology when engaging in long-term surveillance, the SJC has adopted the mosaic theory. See Commonwealth v. McCarthy, 142 N.E.3d 1090 (Mass. 2020). This theory requires that “we consider the governmental action as a whole and evaluate the collected data when aggregated.” Commonwealth v. Henley, 171 N.E.3d 1085 (Mass. 2021). Rather than “asking if a particular act is a search, the mosaic theory asks whether a series of acts that [may not be] searches in isolation amount to a search when considered as a group.” Kerr, The Mosaic Theory of the Fourth Amendment, 111 Mich. L. Rev. 311 (2012). That is, a series of acts may constitute a search even though each individual step in isolation does not. McCarthy; see District of Columbia v. Wesby, 138 S. Ct. 577 (2018).

Under the mosaic theory, to determine if the government’s actions amount to a search, courts consider “whether the surveillance was so targeted and extensive that the data it generated, in the aggregate, exposed otherwise unknowable details of a person’s life.” Commonwealth v. Mora, 150 N.E.3d 297 (Mass. 2020); see Carpenter (“Mapping a cell phone’s location [using targeted CSLI] over the course of 127 days” constituted a search because it revealed “an intimate window into a person’s life” that couldn’t be obtained via traditional surveillance.). In making such a determination, the SJC has focused on “three general concerns: the extent to which the surveillance reveals the whole of an individual’s public movements; the character of the information obtained; and whether the surveillance could have been achieved using traditional law enforcement techniques.” See Henley; Mora; McCarthy. These are the same considerations that federal courts examine when having to decide whether a search has occurred in cases involving surveillance technology. See Carpenter; see, e.g., United States v. Trice, 966 F.3d 506 (6th Cir. 2020), cert. denied, 141 S. Ct. 1395 (2021).

A warrant affidavit must show “a sufficient nexus between the criminal activity for which the probable cause has been established and the physical location of the cell phone recorded by the CSLI.” Commonwealth v. Hobbs, 125 N.E.3d 59 (Mass. 2019). Further, “it is not enough that the object of the search may be found in the place subject to search…. Rather, the affidavit must demonstrate that … the item sought will be located in the particular data file … to be searched.” Commonwealth v. Broom, 52 N.E.3d 81 (Mass. 2016).

Turning to the present case, as to whether these warrants for CSI data were searches, the Court wrote that “because investigators obtained seven tower dumps [collections of subscriber data from relevant cell towers] spanning seven distinct dates over the course of more than one month, [investigators] also were able to piece together a pattern of behavior, that is, not only where an individual was and with whom he or she associated on one occasion, but also where the individual had been and with whom the individual had associated on multiple different occasions.” Further, “investigators were able to compile and catalog the locations of more than 50,000 individuals at varying points over more than one month, without any one of them ever knowing that he or she was the target of police surveillance.” Thus, due to the balance of factors relating to the data sought and the information investigators were able to glean from it, the SJC concluded that obtaining and analyzing this data “intruded upon the defendant’s reasonable expectation of privacy” and constituted a search.

Because the Court concluded that a search had occurred in connection with both search warrants, it then considered whether the warrants were valid by being supported by probable cause. It found that, of the two warrants used in Perry’s case — one obtained by the FBI, and one obtained by the Boston PD — only the second warrant, which was obtained by the Boston PD, was supported by probable cause. The Court addressed the second warrant first, noting that it described in great detail the numerous similarities among the offenses, the presence of a likely getaway driver, eyewitness statement, presence of surveillance video from a nearby business, and facts leading investigators to believe that the suspects communicated with one another from a distance prior to or after the commission of the crimes.

The Court determined that the Boston PD warrant affidavit contained enough details that investigators were able to show the suspect communicated with the getaway driver from such a distance that a cell phone was the most likely means of doing so. These details “combined with the affiant’s statements about the overall ubiquity of cellular telephones, provided reasonable grounds that the robber and the getaway driver had used cellular telephones to communicate,” the Court stated. Thus, the Court concluded that the Boston PD warrant affidavit was supported by probable cause.

Turning to the FBI warrant, the Court noted that it detailed the significant factual similarities among the robberies like the second warrant did; however, it only alleged the ubiquity of cell phones in the commission of crimes as a general matter but failed to provide any additional details establishing a nexus between that generic fact and the specific crimes in question, i.e., it didn’t provide any particularized facts supporting the use of cell phones by the robber and getaway driver to communicate with one another prior to or after the robberies, in contrast to the second warrant. The Court determined that the only alleged fact contained in the first warrant affidavit supporting the claim that the perpetrators used cell phones in connection with the robberies was the affiant’s naked assertion that “it is very common for a person to have a cellular telephone with them at all times.” Thus, the Court concluded that the first warrant was not supported by probable cause and “the evidence obtained pursuant to [it] must be suppressed.”

The Court summarized its analysis of the governing law and application to the facts of this case as follows: “The Commonwealth’s actions in this case intruded upon the defendant’s reasonable expectation of privacy and therefore effectuated a search under art. 14. Nonetheless, because the second warrant was sufficiently particular and supported by probable cause, the evidence obtained pursuant to the second warrant need not be suppressed. All evidence stemming from the tower dumps provided pursuant to the first warrant, however, must be suppressed because the warrant was not supported by probable cause.”

Finally, due to the potentially intrusive and easily abused power to discern the private habits of citizens via CSLI obtained via tower dump warrants, the Court exercised its authority under General Laws c. 211, § 3 to “impose requirements (by order, rule or opinion) that go beyond constitutional mandates” and imposed prospective requirements for any warrant seeking CSLI data.

The Court instructed that only judges may issue search warrants for tower dumps — not magistrates — and any “warrant must include protocols for the prompt and permanent disposal of any and all data that does not fit within the object of the search following the conclusion of the prosecution.” The Court declared that this is a new rule not dictated by existing statute or precedent, so it applies only “prospectively and to those cases that are active or pending on direct review on the date of issuance,” viz., April 1, 2022.

Accordingly, the Court remanded the case with instructions to suppress the data obtained via the FBI’s warrant application. See: Commonwealth v. Perry, 184 N.E.3d 745 (Mass. 2022). 


Editor’s note: The Court does a particularly good job of explaining the mechanics and law enforcement’s use of CSLI and tower dumps. Most readers who use a cell phone would likely learn something by examining the Court’s discussion on this topic. Additionally, anyone with an interest in the law, both federal and Massachusetts, governing warrant requirements for CSLI and tower dumps would benefit from reading the full opinion.

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