Computers, Privacy & the Constitution

I Know Where You Live and I've Seen Where you Sleep: Cell Site Location Data and the Fourth Amendment

-- By EveShabto - 04 Mar 2017


Cellular phones are a staple of the modern American’s life. As of January 2017, 95% of American adults owned a cell phone, and 77% owned smartphones.(1) The Supreme Court has noted that cell phones have become “such a pervasive and insistent part of daily life that the proverbial visitor from Mars might conclude they were an important feature of human anatomy.” (2) Aside from the content stored in cell phones, phones also generate location data: Cell Site location information (“CSLI”).

CSLI Technology

CSLI allows cell service providers to track and store massive amount of information about a user’s physical movements. CSLI is generally divided into two categories: historical data and real-time data. Historical data is location data that has accumulated over time and is stored by the cell service provider, while real-time data is current data that can be used to determine the current location of the cell phone. (3) Although courts have generally held that law enforcement must obtain a warrant before gaining access to real-time CSLI, many courts maintain that historical cell site data is not afforded the same protection. (4)

The Fourth Amendment and the Stored Communications Act

The Fourth Amendment guarantees “[t]he right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures,” and that “no Warrants shall issue, but upon probable cause.” (5) A government search within the meaning of the Fourth Amendment violates “a subjective expectation of privacy that society recognizes as reasonable.” (6) However, law enforcement can obtain historical CSLI without a warrant and merely a court order under the Stored Communications Act (“SCA”) because many jurisdictions consider CSLI “non-content” information, like the address on an envelope. (7) Under the SCA, obtaining non-content information does not require probable cause; only “specific and articulable facts” and “reasonable grounds to believe” the information sought will be “relevant and material” to an investigation. (8)

The original SCA was designed as a statutory stand-in for uncertain Fourth Amendment protection. However, as long as courts consider CSLI to be non-content information, the SCA is entirely inadequate. This paper argues that cell phone users have a reasonable expectation of privacy in their historical CSLI and the Fourth Amendment should apply to CSLI. However, recent Circuit decisions indicate that Courts are not yet willing or able to extend Fourth Amendment protection to CSLI because traditional Third Party doctrine gets in the way. (9) Therefore, Congress should pass legislation (or update the SCA) to afford CSLI greater protection.

Reasonable Expectation of Privacy in CSLI

In order for CSLI to possess Fourth Amendment protection, the traditional Katz two-prong test tells us that individuals must have (1) an actual, subjective expectation of privacy in their CSLI, and (2) society must be prepared to acknowledge that expectation as reasonable. Americans have a subjective expectation of privacy in the CSLI, and the Supreme Court has indicated that Americans have an objective expectation to be free from warrantless government surveillance. (10)


The majority of Americans have no idea that cell phone service provides store their CSLI and regularly allow the government access to those stored records. (11) How can cell phone users assume the risk their CSLI will be shared if they are not aware that the information is being stored in the first place? Furthermore, Americans who are aware that their CSLI is stored and shared with the government still consider CSLI to be sensitive information. (12) In 2014, the Pew Research Center found that 82% of American adults considered data that showed the details of their physical location over time to be more sensitive information than the content of their text messages, relationship history, web browser history, and religious or political views. (13)


Katz's objective prong requires courts to “make a normative finding about whether users should be entitled to view the object of the search as private.”(14) In United States v. Jones, five justices recognized the sensitive nature of location information. Although Jones involved gathering location data with a GPS device, Justice Alito in his concurrence, acknowledged that there are a plethora of devices with tracking capabilities, and he singled out cell phones to be the most considerable. (15) The noted that novel tracking devices will “continue to shape the average person’s expectations about the privacy of his or her daily movements,” suggesting that new surveillance methods will alter the Katz analysis to focus on normative considerations. (16)

Justice Sotomayor, also concurring, expressed her concerns about protecting location information since even short-term GPS monitoring generates a precise, comprehensive record of a person’s public movements that reveal a person’s work, religion, sexual associations, etc. and can be stored and searched years into the future. Furthermore, Sotomayor stated she would “not assume that all information voluntarily disclosed to some member of the public for a limited purpose is, for that reason alone, disentitled to Fourth Amendment protection” because “whatever the societal expectations, [those expectations] can attain constitutionally protected status only if our Fourth Amendment jurisprudence ceases to treat secrecy as a prerequisite for privacy.” (17)

Third Party Doctrine Should Not Apply...

Sotomayor recognized that secrecy may not be a prerequisite for privacy: just because society may disclose certain information to a third party for limited purpose, does not mean that society does not also expect the information to remain private. CSLI is a prime example of this idea. First of all, cell phone users do not voluntarily share CSLI. The data is automatically generated without the user taking any affirmative action and many users have no idea CSLI is generated, let alone stored. However, if users are aware the the data is collected, they reasonably expect that it is used to facilitate cell service and not to generate a comprehensive record of their location, to be shared with law enforcement without any probable cause. (18)

...But It Does. Is there a Possible Statutory Solution?

As the Fourth Amendment and third party doctrine stand, CSLI does not have the protection it deserves. Instead, Congress should update the SCA or pass entirely new legislation that protects CSLI with a warrant requirement. There are currently nine states that have passed state laws requiring law enforcement to obtain a warrant before accessing historical CSLI(19) which indicates there is an appetite for such legislation -- but unfortunately, probably not in our federal Congress. Congress recently passed a resolution to allow ISPs to sell internet-users' browsing history without users consent or knowledge. (20) How did this happen? The telecommunications industry "actively lobbied Congress to roll back broadband privacy protections passed by the FCC".(21) Cell phone service providers are unlikely going to relinquish control over user cell site location information.


In writing for the Web, what's the point of making footnotes? These should be links in the text. Make things easy for the reader.

Substantively, this draft depends on the idea that when two radios are in touch with one another, the fact of the connection "belongs" to the smaller radio, and the owner of the larger radio should for some reason not be able to use that information for its own purposes, and should not be subject to legal requests for it.

Somehow, then, the Fourth Amendment is supposed to cover a subject which it had no prior connection with, because we need privacy and we can't believe that we lost it without doing something about it. I'm sympathetic, but I did spend weeks trying to explain in detail why this won't work and the history can't be assumed away. Now, without making any reference to what I said on the subject, you've simply asserted that because we need the location of the other fellow's radio that we put ourselves in touch with to be private, it is private, and not only private, but the government should need a search warrant, not a subpoena, to get it.

But this makes no sense. If you want the cellular service provider not to know where you are, your phone has to be off, or you have to leave it somewhere else. The US Constitution doesn't dictate that you rather than the service provider have a right to data generated by the fact that your two radios were in touch, let alone that these radio signals are so sacred that government needs a search warrant for the fact of the connections. If you're going to make that argument, it has to be based on more than assertion of need: there has to be some relationship between the legal doctrine for which you are contending and the prior history of the constitutional provision. Otherwise, you are just making up constitutional law.

You are entitled to restrict access to your paper if you want to. But we all derive immense benefit from reading one another's work, and I hope you won't feel the need unless the subject matter is personal and its disclosure would be harmful or undesirable. To restrict access to your paper simply delete the "#" character on the next two lines:

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1 : See Mobile Technology Fact Sheet, PEW RES. CENTER,

2 : Riley v. California, _ U.S. _, 134 S. Ct. 2473, 2484 (2014)

3 , 11 , 14 : Lauren E. Babst, Note, No More Shortcuts: Protect Cell Site Location Data With a Warrant Requirement, 21 Mich. Telecomm. & Tech. L. Rev. 363 (2015)

4 :

5 : U.S. Const. amend. IV

6 : U.S. See, e.g., Jones v. United States, 357 U.S. 493, 497-499 (2012); Katz v. United States, 389 U.S. 347 (1967)

7 , 8 : 18 U.S.C. 2703 (2012)

9 : United States v. Graham, 824 F.3d 421 (4th Cir. 2016) (en banc); United States v. Carpenter, 819 F.3d 880 (6th Cir. 2015); United States v. Davis, 785 F.3d 498 (11th Cir. 2015) (en banc); In re Application of United States for Historical Cell Site Data, 724 F.3d 600, 610 (5th Cir. 2013); In re United States for an Order Directing a Provider of Elec. Commc’n Serv. to Disclose Records to the Gov’t, 620 F.3d 304, 317 (3d Cir. 2010)

10 : Katz v. United States, 389 U.S. 347(1967)

12 : Jennifer King & Chris Jay Hoofnagle, Research Report: A Supermajority of Californians Supports Limits on Law Enforcement Access to Cell Phone Location Information 8-9 (Apr. 18, 2008)(unpublished manuscript), available at


15 : United States v. Jones, 565 U.S. 400, 428 (2012)

16 : Id

17 : United States v. Jones, 565 U.S. 400, 416 (2012) (Sotomayor, J., concurring) (expressing doubt that people “reasonably expect that their movements will be recorded and aggregated in a manner that enables the Government to ascertain... their political and religious beliefs, sexual habits, and so on.”)

18 :

19 : _See_

20 : See

21 : _See_


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r16 - 09 May 2017 - 04:40:34 - EveShabto
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