February 17, 2020 | Becca Badon
Edited by Sam Richter
Privacy is the fundamental human right to maintain a degree of confidentiality in our personal lives and control where our information goes. In the age of decentralization, interconnectivity, and endless innovation, what is included in our “right to privacy” and what are the limits of its protection? Put simply, how does privacy work in an age where our information is rapidly moving out of our control? These questions were at the core of the 2018 Supreme Court case, Carpenter v. United States.
In April of 2011, the police arrested four men in connection with a series of armed robberies in Michigan and Ohio. One of the four confessed to the crime and provided the FBI with his cell phone, from which the FBI obtained the phone numbers associated with calls made around the times of the robberies.The FBI then submitted a request to obtain the cell phone carrier’s transactional records for the sixteen phone numbers they had acquired. A magistrate judge approved this request and the carriers handed over the transactional records, in line with the Stored Communications Act. These records contained, among other things, detailed records of the historical cell site location information of the phones.
Timothy Carpenter was one of the people whose phone number had been gathered. Through this process, law enforcement accessed 127 days of historical cell site records which provided a detailed breakdown of Carpenter’s movements, ultimately placing him near the scenes of the robberies. Carpenter was convicted on several counts of aiding and abetting a robbery that affected interstate commerce and another count of aiding and abetting the use or carriage of a firearm during a federal crime of violence and sentenced to 116 years in prison. Carpenter appealed to the 6th Circuit Court of Appeals and eventually up to the Supreme Court, claiming that the FBI’s failure to obtain a warrant before acquiring and using Carpenter’s historical cell site location information constituted a violation of his 4th Amendment protection from unreasonable searches and seizures. In 2018, the Supreme Court ruled 5-4 in favor of Carpenter, striking down the FBI’s actions as an unconstitutional violation of the 4th Amendment. In his opinion, Chief Justice John Roberts looked first to legal precedent, finding similarities with United States v. Miller and United States v. Jones. Despite the similarities he finds in the kinds of constitutional questions being considered, he ultimately concludes that Carpenter falls into a category of its own.
In order to understand the Carpenter decision, it is first important to understand some of its critical components. The first important concept is historical cell site location information. Cell towers are used to receive and transmit cell signals in the most efficient way. As a user moves with his or her phone (regardless of whether the phone is being used or not), the signal bounces off of these towers. As these signals are recorded, it becomes possible to pinpoint the location of that individual to a great degree of precision. This effect is further amplified in cities where cell towers are tightly clustered. In making his overarching privacy argument, Chief Justice Roberts writes that,
Mapping a cell phone’s location over the course of 127 days provides an all-encompassing record of the holder’s whereabouts [providing] 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”.
Because cell phones stay with their users at nearly every moment in the day, tracking a cell phone for such a period of time will inevitably reveal the most personal and private aspects of someone’s life.
Aside from the intrusion that tracking in this way would be, it is also a vast expansion of law enforcement’s power, as “cell phone location information is detailed, encyclopedic, and effortlessly compiled”, thus allowing the government to access information of unprecedented detail and precision at no cost and with few restraints on its ability to use it.
In addition to historical cell site location information, it is also important to understand the role of the Third Party Doctrine and why Carpenter is a deviation from this rule. The Third Party Doctrine is an important piece of legal doctrine dictating the limits of privacy. Under this doctrine, information voluntarily given to third parties (such as banks, phone companies, etc.) is no longer considered private information, and thus the people providing it can no longer claim a reasonable expectation to privacy. The FBI acted under this doctrine when they requested transactional records from carrier companies. In considering legal precedent, it at first seems difficult to understand why Carpenter could constitute a deviation from this rule. The answer that Chief Justice Roberts gives to this important question is at the core of what makes this case a landmark privacy case. In his opinion, he writes,
Cell phones and the services they provide are such a “pervasive and insistent part of daily life” that carrying one is indispensable to participation in modern society…Apart from disconnecting the phone from the network, there is no way to avoid leaving behind a trail of location data. As a result, in no meaningful sense does the user voluntarily “assume the risk” of turning over a comprehensive dossier of his physical movements.
Under the existing interpretation of the Third Party Doctrine, one would have to completely disconnect from modern technology to maintain a reasonable expectation of privacy and protect his or herself from such an invasive search.
The Carpenter v. United States case was a big step in the right direction towards ensuring that legal doctrine and Supreme Court jurisprudence continue to adapt and evolve in step with technological change. Modern times are characterized by technology that is rapidly changing and improving. With these changes will inevitably come many new legal questions. The Carpenter case is a great example of existing legal doctrine being challenged as the characteristics of society today are considered in contrast to the past. Acknowledging the indispensable role that technology plays in our lives today, in addition to the vast capabilities that it possesses, will enable us to legislate and adjudicate in a way that is responsive to the needs of society as they are today and will be tomorrow.
Becca is a junior majoring in International Studies with a focus in Chinese.
 “Carpenter v. United States.” Oyez. November 9, 2019. https://www.oyez.org/cases/2017/16-402
 “Cell Site Location Information.” Electronic Frontier Foundation.
 Carpenter v. United States, 585 U. S. ____, (2018).
 “What You Need to Know About the Third-Party Doctrine”. The Atlantic. December 30, 2013.
 Carpenter v. United States, 585 U. S. ____, (2018).
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