When the government employs new technology to obtain sensitive personal information in a way that diminishes the degree of privacy that individuals reasonably expected prior to the technology’s adoption, it conducts a search under the Fourth Amendment. Applying this principle in United States v. Jones, 565 U.S. 400 (2012), five Justices concluded that longer-term GPS tracking of a car violates reasonable expectations of privacy. Tracing a person’s geographical movements reveals highly sensitive personal information, and prior to the digital age, people reasonably expected that police in most investigations would not have followed a person and recorded her every movement for days or weeks on end.
Likewise government agents engage in a Fourth Amendment search when they intrude on an expectation of privacy that society is prepared to recognize as reasonable. Kyllo v. United States, 533 U.S. 27, 33 (2001); Katz v. United States, 389 U.S. 347, 361(1967) (Harlan, J., concurring). The touchstone for determining when an expectation of privacy is reasonable is “the everyday expectations of privacy that we all share.” Minnesota v. Olson, 495 U.S. 91, 98 (1990). For example, this Court held in Katz that the Fourth Amendment applies to conversations transmitted over telephone lines because phones played a “vital role” in conducting the type of communication previously treated as “private.” 389 U.S. at 352-53.
As new technology has dramatically lowered the cost of government surveillance and increased the government’s access to private information, this Court has stressed that the reasonable-expectation of privacy inquiry must “assur[e] preservation of that degree of privacy against government that existed” prior to the advent of the new technology in question. United States v. Jones, 565 U.S. 400, 406 (Scalia, J.) (alteration in original); id. at 420 (Alito, J., concurring in the judgment); Kyllo, 533 U.S. at 34; see also Riley v. California, 134 S. Ct. 2473, 2490 (2014) (requiring a warrant to search contents of cell phones seized incident to arrest in order to preserve degree of privacy enjoyed before invention and pervasive use of cell phones).
Applying this framework in United States v. Jones, five Justices agreed that people have a reasonable expectation of privacy in “longer term GPS monitoring in investigations of most offenses.” Jones, 565 U.S. at 430 (Alito, J., concurring in the judgment); id. at 415 (Sotomayor, J., concurring). Because GPS monitoring of a car tracks “every movement” a person makes in that vehicle, id. at 430 (Alito, J., concurring in the judgment), it generates extremely sensitive and private information that “enables the Government to ascertain, more or less at will, [people’s] political and religious beliefs, sexual habits, and so on,” id. at 416 (Sotomayor, J., concurring). Prior to the digital age, this information would have been largely immune from search. Although historically the government could have tasked a team of agents with surreptitiously tailing a suspect, doing so “for any extended period of time was difficult and costly and therefore rarely undertaken.” Id. at 429 (Alito, J., concurring in the judgment). Therefore, “society’s expectation has been that law enforcement agents and others would not—and indeed, in the main, simply could not—secretly monitor and catalogue every single movement of an individual’s car for a very long period.” Id. at 430.
For the same reason that five Justices concluded that there is a reasonable expectation of privacy in longer-term GPS monitoring of a car, there is a reasonable expectation of privacy in longer-term cell phone location records. Any other conclusion would allow the government to circumvent the principle accepted by five Justices in Jones through the simple expedient of obtaining cell phone location records. People use their cell phones throughout the day—when they are at home, work, or school, when they are in the car or on public transportation, when they are shopping or eating, and when they are visiting the doctor, a lawyer, a political associate, or a friend. People even keep their phones nearby and turned on while they are asleep. Indeed, “nearly three-quarters of smart phone users report being within five feet of their phones most of the time, with 12% admitting that they even use their phones in the shower.” Riley, 134 S. Ct. at 2490.
“[D]etails about the location of a cell phone can provide an intimate picture of one’s daily life.” State v. Earls, 70 A.3d 630, 642 (N.J. 2013). Historical cell site location information “can reveal not just where people go—which doctors, religious services, and stores they visit—but also the people and groups they choose to affiliate with and when they actually do so.” Commonwealth v. Augustine, 4 N.E. 3d 846, 861 (Mass. 2014) (quoting Earls, 70 A.3d at 642). And to state the obvious, when people make a “visit to a gynecologist, a psychiatrist, a bookie, or a priest,” they typically “assume that the visit is private.” United States v. Davis, 754 F.3d 1205, 1216 (11th Cir. 2014) (Sentelle, J.), rev’d en banc, 785 F.3d 498 (11th Cir. 2015).