Carpenter v. United States: Keeping Up With Technology

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Written By: Jonathan Brown

Member, American Journal of Trial Advocacy

In a nation where there are more cell phone service accounts than people[1], Americans are becoming more attached to their cell phones than ever. People are no longer just carrying their phones everywhere, they are actively using them throughout the day. Whether on social media or other ‘apps,’ a report in 2017 stated that Americans are spending up to five hours per day on their cell phones.[2] Technology is constantly evolving, and the courts are attempting to keep up.

Interpreting the Fourth Amendment’s protections regarding technology, and data has been an ongoing battle for the Court. With the increase in usage, “federal appellate courts have provided little guidance about what the Fourth Amendment requires of law enforcement agents before they may obtain our electronic communications.”[3] This lack of guidance has resulted in case law from the “1970s and 1980s that addressed primitive ancestors of the electronic communications technologies in use today” applying to modern day technological advances. The Supreme Court recently updated the case law with their holding in Carpenter v. United States, stating that cell-site location information data is protected by the Fourth Amendment.[4]


To understand the issue, one must understand what was obtained by the government in Timothy Carpenter’s case. Smartphones connect to a wireless network several times per minute whenever the signal is on, generating a record known as a cell-site location information (CSLI).[5] Similar to cell phone records of calls, cell phone companies collect the data from the CSLI.[6] As the Court noted, “in recent years phone companies have also collected location information from the transmission of text messages and routine data connections . . . modern cell phones generate increasingly vast amounts of increasingly precise CSLI.”[7] This data was obtained without a warrant and used to prosecute Carpenter.

Carpenter was arrested and charged with six counts of robbery and six counts of carrying a firearm during a federal crime of violence.[8] During his trial, Carpenter was identified by seven of his ‘confederates’ as the leader of the operation.[9] Additionally, an FBI Agent testified the CSLI data points obtained and produced “maps that placed Carpenter’s phone near four of the charged robberies.”[10] Carpenter was convicted and sentenced to more than 100 years in prison.[11]

Carpenter appealed the conviction, specifically how the Government obtained his CSLI data points. On appeal, the Sixth Circuit affirmed the conviction holding that “Carpenter lacked a reasonable expectation of privacy in the location information collected by the FBI because he had shared that information with his wireless carriers.”[12] Carpenter then appealed to the Supreme Court.

Prosecutors, obtained the CSLI for 127 days, containing 12,898 location points, an average of 101 data points a day.[13] Simply put, the prosecutors obtained over 12,898 locations that Carpenter visited, over the course of the string of robberies. They obtained this information under the Stored Communications Act which requires that the Government “offers specific and articulable facts showing that there are reasonable grounds to believe” that the information sought is material and relevant to the investigation, which is a lower bar than a warrant requires.[14] Carpenter argued that the seizure of records violated his Fourth Amendment rights because they were obtained without a warrant.[15]

Brief History of the Fourth Amendment

The Supreme Court has recognized that the purpose of the Fourth Amendment “is to safeguard the privacy and security of individuals against arbitrary invasions by government officials.”[16] This safeguard has been constantly evolving to keep up with ever-expanding technological advances. For years the Court followed the holding in United States v. Jones which focused on whether the government physically intruded on a constitutionally protected area.[17] In 1967, the Court “expanded [their] conception of the [Fourth] Amendment to protect certain expectations of privacy.”[18] In Katz v. United States, the Court established that the Fourth Amendment is meant to protect people, not places.[19] This was a departure from the Jones decision. The Court has placed an importance on upholding the central aim of the Framers, which was “to place obstacles in the way of a too permeating police surveillance.”[20]

As technology began to advance at a dramatic rate, the Court had to ensure that the Framer’s central aim of the Fourth Amendment was not lost. In Kyllo v. United States,the Court rejected a “mechanical interpretation” of the Fourth Amendment and ensured that privacy was still protected.[21] The Court held that the use of a thermal imaging device to detect heat in a house was a search.[22] Perhaps foreshadowing further technological advancements, the Court determined that any other decision in Kyllo would leave homeowners “at the mercy of advancing technology” thus “absent a warrant [the Government] could not capitalize on such new sense enhancing technology to explore what was happening within the home.”[23] Further, the Court stated that it “must take account of more sophisticated systems that are already in use or development.”[24]

With the ease that information is shared with others, in Carpenter the Court had to determine what protections should be given to the access of the CSLI data. The Court had previously held that a “person has no legitimate expectation of privacy in information he voluntarily turns over to third parties.”[25] In Smith v. Maryland, the Court held that since a person voluntarily gives over cell phone data by using the phones, there is no Fourth Amendment protection regarding the numbers dialed by an individual.[26] This is what was at issue in Carpenter, along with an individual’s right to privacy in their movements. While the Court held in United States v. Knotts that the police could place a beeper on a container and then monitor its movements, they cautioned against the legality of the state or government using “twenty-four hour surveillance” to monitor a citizen.[27] Following the decision in Knotts, 30 years later the Court addressed the issue of a sophisticated surveillance in United States v. Jones.[28] In Jones,the Court held that placing a GPS tracking device on a vehicle and then monitoring the vehicle’s movements constitutes a search.[29] The Court held this was a search because of the trespass involved, but five justices mentioned that concerns would be raised by “conducting GPS tracking of his cell phone.”[30]

The Decision

At the cross section of these cases is Carpenter. Citing to the unique nature of cell phone location records, the Court declined to extend Smith and Miller.[31] The Court held in Carpenter that because of the “deeply revealing nature of CSLI, its depth, breadth, and comprehensive reach, and the inescapable and automatic nature of its collection” it does not matter that the data was turned over to a third party, it still warrants protection under the Fourth Amendment.[32] The Court determined that since the CSLI information is protected under the Fourth Amendment, the Government conducted what amounted to a search without a warrant when they obtained the information.[33] The Court stated that “an individual maintains a legitimate expectation of privacy in the record of his physical movements as captured through CSLI”.[34] The Court explained that in this day and age, even though an individual may expect a company to have records of their locations, “that distinction does not negate Carpenter’s anticipation of privacy in his physical location.”[35]

The Future

By determining that the automatic nature of the transferred data to a third party does not fall under the Court’s holding in Smith, the Court is potentially foreshadowing what is to come in regard to the future of the Fourth Amendment and technology. Interestingly, the Court compared the tracking of a cell phone to an ankle monitor.[36] Perhaps wanting to curtail the Government’s growing surveillance powers, the majority opinion also noted that “when the Government tracks the location of a cell phone it achieves near perfect surveillance.”[37] The Court also noted the difference in retrieving the location logs of cell phones with that of placing a GPS tracker on a vehicle.[38] In essence, every American with a cell phone is currently being tracked and their location is being logged.[39] The Court’s decision in Carpenter places obstacles in the way of the Government obtaining information about Americans.

Of future importance the Court also mentioned the “nature of the particular documents sought” and the “voluntary disclosure” of the information.[40] This standard and view of the data generated by cell phones is likely to be used when assessing other information and data. Likely in the spirit of Kyllo, the Court made this decision knowing the ever-advancing technology the Government has.

With social media and smartphones, more information is being put into the public without our knowledge. According to the decision in Katz this information should still be protected because, “what [one] seeks to preserve as private, even in an area accessible to the public, may be constitutionally protected.”[41] Without the protections of the Fourth Amendment the Government could obtain this data without a warrant. The Court’s decision does not stop the Government from obtaining the location data. It merely makes it more difficult, which was one of the Founders’ purposes of the Fourth Amendment.[42] It will be interesting to see how this holding is interpreted in regard to other forms of information that is automatically turned over to third parties. At least now there is recent case law to help guide the lower courts. One can only hope that the Supreme Court will attempt to keep up with technology and not leave the lower courts with no guidance on new issues that ever-advancing technology is sure to cause.

[1] Carpenter v. United States, 138 S.Ct. 2211 (2018).

[2] Sarah Perez, US Consumers now spend 5 hours per day on mobile devices, TeleCrunch (May 3, 2017),

[3] Susan Freiwald, Cell Phone Location Data and the Fourth Amendment: A Question of Law not Fact. 70 Md. L. Rev. 681, 681 (2011).

[4] Carpenter, 138 S.Ct. at 2200.

[5] Id. at 2211.

[6] Id. at 2212.

[7] Id.

[8]See Carpenter, 138 S. Ct. at 2212 (“Carpenter was charged with six counts of robbery and an additional six counts of carrying a firearm during a federal crime of violence.”); see 18 U.S.C. §§ 924(c), 1951(a)).

[9] Carpenter, 138 S.Ct. at 2212.

[10] Id. at 2212-13.

[11] Id. at 2213.

[12] Id.

[13] Id. at 2212.

[14] Id. (quoting 18 U.S.C. § 2703(d)).

[15] Carpenter, 138 S.Ct. at 2212.

[16] Camera v. Mun. Court of City and County of San Francisco, 387 U.S. 523, 528 (1967).

[17] 565 U.S. 400, 405, 406, n.3 (2012).

[18] 389 U.S. 347, 351 (1967).

[19] Id.

[20] United States v. Di Re, 332 U.S. 581, 595 (1948).

[21] 533 U.S. 27, 35 (2001).

[22] Id. at 34-35.

[23] Carpenter, 138 S.Ct. at 2214.

[24] Kyllo, 533 U.S. at 36.

[25] Smith v. Maryland, 442 U.S. 735, 743-44 (1979).

[26] Id. at 740.

[27] 460 U.S. 276 (1983).

[28] 565 U.S. 400 (2012).

[29] Id. at 404-405.

[30] Id. at 410; Carpenter, 138 S.Ct.. at 2215.

[31] Carpenter, 138 S.Ct. at 2217.

[32] Id. at 2223.

[33] Id.

[34] Id. at 2217.

[35] Id.

[36] Id. at 2218.

[37] Carpenter, 138 S.Ct. at 2218.

[38] Id.

[39] Id.

[40] Id. at 2219 (quoting United States v. Miller, 425 U.S. 435, 442 (1976)); Id. at 17 (citing Smith, 442 U.S. at 745 (“[I]n no meaningful sense does the user voluntarily ‘assume[] the risk’ of turning over a comprehensive dossier of his physical movements.”)).

[41] Carpenter, 138 S.Ct. at 2217 (quoting Katz, 389 U.S. at 351-52).

[42] Di Re, 332 U.S. at 595.

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