Observación

Chief Justice Roberts wrote the majority opinion in Carpenter, which held that “the [g]overnment conducts a search under the Fourth Amendment when it accesses [seven days of] historical cell phone records that provide a comprehensive chronicle of the user’s past movements.”312

He began with a brief exposition of Fourth Amendment fundamentals, pointing out that the Amendment’s “basic purpose . . . is to safeguard the privacy and security of individuals against arbitrary invasions by governmental officials.”313 _Borrowing substantially from the Court’s opinion in Riley, he explained that the Framers drafted the Amendment “as a ‘response to the reviled “general warrants” and “writs of assistance” of the colonial era, which allowed British officers to rummage through homes in an unrestrained search for evidence of criminal activity.’”314

Chief Justice Roberts next invoked Katz, explaining that “the Fourth Amendment protects people, not places.”315 _{He went on to note} that “[w]hen an individual ‘seeks to preserve something as private,’ and his expectation of privacy is ‘one that society is prepared to recognize as reasonable,’ . . . official intrusion into that private sphere generally qualifies as a search and requires a warrant supported by probable cause.”316

The Chief Justice also emphasized that one of the “basic guideposts”317 _{of the Fourth Amendment is “to place obstacles in the} way of a too permeating police surveillance.”318

Pointing to Kyllo v. United States319 _{and Riley as examples, he further reflected on the}

311. Id. at 887.

312. Carpenter v. United States, 138 S. Ct. 2211, 2211, 2217 n.3 (2018).

313. Id. at 2213 (quoting Camara v. Mun. Court of S.F., 387 U.S. 523, 528 (1967)). 314. Id. (quoting Riley v. California, 573 U.S. 373, 403 (2014)).

315. Id. (quoting Katz v. United States, 389 U.S. 347, 351 (1967)). 316. Id. (quoting Smith v. Maryland, 442 U.S. 735, 740 (1979)). 317. Id. at 2214.

318. Id. (quoting United States v. Di Re, 332 U.S. 581, 595 (1948)).

319. Kyllo v. United States, 533 U.S. 27 (2001). At issue in Kyllo was law enforcement’s use of a thermal-imaging device to scan the defendant’s home without a warrant “to determine

Court’s evolving application of a less mechanical and more nuanced application of pre-digital Fourth Amendment doctrines in the face of technological innovation and the government’s enhanced surveillance capabilities.320

Chief Justice Roberts then explained that the “personal location information maintained by a third party . . . lie[s] at the intersection of two lines of [Fourth Amendment] cases.”321

The first set of those cases,

United States v. Knotts322 _{and Jones, establish the boundaries of an} individual’s privacy interest in his physical location and movements.323 The Chief Justice distinguished Knotts, which held that police were not required to obtain a warrant to track a beeper they had placed in a suspect’s car, from Jones, which held that the police’s warrantless placement of a GPS tracking device on a suspect’s car and subsequent twenty-eight-day surveillance of that vehicle’s movements ran afoul of the Fourth Amendment.324

In the majority’s view, the important differences between Knotts and Jones revolve around the varying levels of sophistication and pervasiveness of the law enforcement surveillance systems at issue in each case. While Knotts involved “rudimentary tracking facilitated by the beeper . . . during a discrete ‘automotive journey,’”325 _{Jones encompassed “sophisticated} surveillance,” which tracked the target’s “every movement” over an approximately four-week-long time period.326

The Court then shifted to the second line of cases implicated by the FBI’s warrantless collection of Carpenter’s CSLI: Miller, Smith, and the third-party doctrine.327 _{As the Court saw it, “[t]here is a world} of difference between the limited types of personal information

whether an amount of heat was emanating from petitioner’s home . . . consistent with the use of [high-intensity] lamps” typically used for indoor marijuana growth. Id. at 29. After acknowledging that “[i]t would be foolish to contend that the degree of privacy secured to citizens by the Fourth Amendment has been entirely unaffected by the advance of technology,” the Court analyzed the issue presented under the two-part Katz test. Id. at 33–35. The Court subsequently concluded that “[w]here . . . the Government uses a device that is not in general public use, to explore details of the home that would previously have been unknowable without physical intrusion, the surveillance is a ‘search’ and is presumptively unreasonable without a warrant.” Id. at 40.

320. Carpenter, 138 S. Ct. at 2214. 321. Id.

322. United States v. Knotts, 460 U.S. 276 (1983). 323. Carpenter, 138 S. Ct. at 2215.

324. Id.

325. Id. (quoting Knotts, 460 U.S. at 285).

326. Id. (quoting United States v. Jones, 565 U.S. 400, 430 (2012) (Alito, J., concurring in the judgment)).

addressed in Smith and Miller and the exhaustive chronicle of location information casually collected by wireless carriers today.”328

The Chief Justice went on to say that

[g]iven the unique nature of cell phone location records, the fact that the information is held by a third party does not by itself overcome the user’s claim to Fourth Amendment protection. Whether the Government employs its own surveillance technology as in Jones or leverages the technology of a wireless carrier, we hold that an individual maintains a legitimate expectation of privacy in the record of his physical movements as captured through CSLI. The location information obtained from Carpenter’s wireless carriers was the product of a search.329

Perhaps most notably, the Chief Justice invoked both of the third- party doctrine’s limiting principles discussed above while distinguishing Miller and Smith. First, he rejected the government’s argument that the third-party doctrine operates categorically and without constraint to eviscerate any Fourth Amendment protection for records maintained by a commercial entity, insisting that Miller and

Smith “did not rely solely on the act of sharing.”330 _{Instead, those cases} require courts to consider “‘the nature of the particular documents sought’ to determine whether ‘there is a “legitimate expectation of privacy” concerning their contents.’”331

The Court then held that historic CSLI was entitled to Fourth Amendment protection because such information constitutes “a detailed chronicle of a person’s physical presence compiled every day, every moment, over several years” and, thus, “implicates privacy concerns far beyond those considered in Smith and Miller.”332

Second, the Court rejected the contention that Carpenter voluntarily disclosed his CSLI to his wireless carriers.333

It observed that CSLI “is not truly ‘shared’ as one normally understands the term” for two reasons334

: (1) because cell phones are “indispensable to participation in modern society,” carrying one may not actually be a

328. Id. at 2219. 329. Id. at 2217. 330. Id. at 2219.

331. Id. (quoting United States v. Miller, 425 U.S. 435, 442 (1976)). 332. Id. at 2220.

333. Id. at 2219. 334. Id.

completely voluntary choice;335 _{and (2) cell phones are constantly in} connection with cell sites and, thereby, generate CSLI “without any affirmative act on the part of the user beyond powering up.”336 Consequently, Carpenter had not “voluntarily ‘assume[d] the risk’ of turning over a comprehensive dossier of his physical movements.”337

The Court also held that individuals have a reasonable expectation of privacy in CSLI.338

Relying on the Jones concurrences, Chief Justice Roberts announced that society can reasonably expect law enforcement to refrain from monitoring and cataloguing an individual’s every movement.339 _{Analogizing CSLI surveillance to the} GPS monitoring at issue in Jones, he further observed that “the time- stamped [CSLI] data provides an intimate window into a person’s life, revealing not only his particular movements, but through them his familial, political, professional, religious, and sexual associations.”340 This is because “[a] cell phone faithfully follows its owner beyond public thoroughfares and into private residences, doctor’s offices, political headquarters, and other potentially revealing locales.”341 Finally, the Court expressed concern that “the retrospective quality of the [CSLI] gives police access to a category of information otherwise unknowable” and the only limit on the government’s ability to gather CSLI is the length of time the wireless carriers retain the data, “which currently [is] for up to five years.”342

The Chief Justice concluded Carpenter by characterizing it as a “narrow” decision so as not to “embarrass the future.”343

He emphasized that Miller and Smith were still good law insofar as they apply to “conventional surveillance techniques and tools, such as security cameras.”344 _{The Court also explained that the case did not} extend to “other collection techniques involving foreign affairs or national security.”345 335. Id. 336. Id. 337. Id. 338. Id. at 2217. 339. Id.

340. Id. (quotations omitted) 341. Id. at 2218 (emphasis added).

342. Id.

343. Id. at 2220 (quoting Nw. Airlines, Inc. v. Minnesota, 322 U.S. 292, 300 (1944)). 344. Id.