Tracking a User's Location via Cell Phone

Privacy Implications

A hot issue currently being debated in the courts involves the intersection of privacy law and technology: the ability to use cellular phone signals to track the location of users. As communications technology grows more powerful, it becomes easier to collect information on consumers that subscribe to services such as cell phone providers and GPS locators, which require constant interaction with towers or satellites. The government has seized upon the ability to track people using this electronic data in order to strengthen its investigatory practices.

The argument for easy access to such information is that particularly in the age of increased awareness of and sensitivity to the potential for domestic terrorism, knowing the location of possible perpetrators is crucial to uncovering and shutting down criminal activity as quickly as possible. However, the high potential for abuse of the privacy rights of individuals that use these services is serious enough that the Department of Justice has been taken to court repeatedly in recent months, in order to determine just where the line between legitimate investigation and protection of privacy should be drawn.

The purpose of this article is to discuss recent cases that address the standard that courts have placed upon investigators to procure real-time tracking information from data communications companies.

For a cellular phone to readily receive calls there must be continuous communication between the physical phone and the service provider’s satellite towers. This signal can be used by phone companies to track the whereabouts of individuals. Developing technology coupled with an increasing number of cell sites built to handle the rapidly expanding cell phone market have led to increased accuracy in triangulating the physical location of a user. A useful tool for locating 911 callers from their cell phones,1 the service can be used to track any individual with a cell phone that is powered on, regardless of whether or not the user is engaged in a call.

Law enforcement officials have long used data stored by cell phone service providers to track individuals suspected of committing crimes, but no statute clearly sets out the standard for what evidence is needed before court-ordered disclosure of this information may be granted. Recently a number of decisions have been passed down discussing cell phone tracking and the standard by which law enforcement officials may request data to locate an individual via their cell phone. Of the six decisions handed down (from the Eastern District of New York, Southern District of Texas, District of Maryland, Southern District of New York,

District Court for the District of Columbia and Eastern District of Wisconsin),2 four ruled that a search warrant based on probable cause is required before law enforcement can track someone’s location using cell phone data.3 Although judges have urged the Department of Justice to appeal the rulings so that a uniform standard can bring clarity to the issue, the DOJ has declined to do so. The lone case rejecting probable cause as the required standard was handed down in December 2005 from the Southern District of New York.4

The issue raised in these cases is whether “real-time” cell site information that locates a user, regardless of whether or not they are engaged in a call, requires a different burden than requesting pen register information (a record of outgoing calls from a particular number) or trap and trace information (a record of incoming calls to a particular number). In the absence of legislation regarding cell site tracking information, the government has argued that a combination of two statutes provides the right to request such information at a standard lower than probable cause: the Stored Wire and Electronic Communications and Transactional records Access Act (“SCA”), 18 U.S.C. § 2701 et seq., and 18 U.S.C. § 3121 et seq. (the “Pen/Trap statute”). The SCA gives the government access to “a record or other information pertaining to a subscriber to or a customer of such service (not including the contents of communications).”5 The government can access this information via court order if it “offers specific and articulable facts showing that there are reasonable grounds to believe that.the records or other information sought are relevant and material to an ongoing criminal investigation.”6 Because the SCA refers to records of calls completed, not real-time tracking data such as the information the government has sought to obtain, this cannot be the sole statute under which the government seeks information disclosing the physical location of its targets.7

In order to obtain authorization for installation of a pen register and trap/trace device under the Pen/Trap statute, the government must only assert that the information requested is “relevant to an ongoing criminal investigation.”8 The government argues that the USA PATRIOT Act of 20019 now includes real-time cell site information within the definitions of both “pen register” and “trap and trace device.”10 The consequence of that expansion is under debate, because in 1994 Congress amended the SCA by passing the Communications Assistance for Law Enforcement Act (“CALEA”).11 CALEA prohibits the disclosure of “any information that may disclose the physical location of the subscriber” when the government seeks such information “solely pursuant to the authority for pen registers and trap and trace devices.”12 The government asserts that by working pursuant to both the SCA and the Pen/Trap statute, it has the right to obtain such information without probable cause or a search warrant. Four courts have rejected this, stating that as the SCA does not refer to real-time data, and the Pen/Trap statute gives no right to information tracking a user’s location, the only way to grant the government access to such information is under Federal Rule of Criminal Procedure 41(d)(1), which requires a showing of probable cause before a search warrant is issued.13

The government has also argued that there is no Fourth Amendment implication in the communication between the cell phone and a cell tower. Thomas Brown, the Assistant U.S. Attorney who ran the case in the Southern District of New York, asserted in court documents that a “cell phone user voluntarily transmits a signal to the cell phone company, and thereby ‘assumes the risk’ that the cell phone provider will reveal to law enforcement the cell site information. This is not a privacy expectation that society is prepared to view as reasonable.”14 Although neglecting to decide whether the government had the ability to procure tracking information without a court order, Judge Bredar of the District of Maryland disagreed: “[t]hose who choose to carry a cell phone.cannot reasonably be deemed to have consented to the tracking of their movement by the government.”15

As of yet, the lone voice of dissent has come from the Southern District of New York. Judge Gorenstein’s opinion considered the entire matter, although he distinguished the three cases preceding this one, as the information sought by the government was only related to phone calls made by the user of the target phone, not the continuous communication between cell sites and a phone not engaged in a call. In addition, the Judge opined that there could be no triangulation of a call from the user of the phone because data only relates “to a single cell tower with which the cell phone is communicating.”16 Judge Gorenstein adopted a broad interpretation of the PATRIOT Act expansion of the definition of “pen register,” and stated that because CALEA purposefully excludes physical location information, such information would have to be available under the Pen/Trap statute to give meaning to the CALEA provision. Also, because the Pen/Trap statute has language that a pen register may be installed only “pursuant to ‘a court order under section 3123,'” a search warrant granted solely under Rule 41 may not be an option.17

On January 6, 2006, the District Court of the District of Columbia handed down its decision, which also dealt with a government request to track the location of a cell phone user during incoming and outbound calls. The District Court agreed with the three opinions that denied the government requests for real-time information when probable cause was not shown. Judge Facciola wrote:

It is inconceivable to me that the Congress that precluded the use of the Pen Register statute to secure in 1994 ‘transaction data’.nevertheless intended to permit the government to use that same secure the infinitely more intrusive information about the location of a cell phone every minute of every day that the cell phone was on. I cannot predicate such a counter-intuitive conclusion on the single word ‘solely.’18


Until higher courts are asked to address the issue of what proof is required before real-time tracking information must be disclosed, any conclusions that can be drawn are strictly regional. As the Department of Justice has not appealed the cases in which a search warrant for cell cite information was required to be based upon probable cause, in jurisdictions where such rulings have been handed down (the Eastern District of New York, Southern District of Texas, District of Maryland and District of Washington, DC), a search warrant issued by the court is the only document a company in possession of real-time tracking information must respond to. In the Eastern District of Wisconsin, something more than “specific, articulable facts” will be required, but whether a search warrant based upon probable cause is necessary has not been decided. Because search warrants must request specific information, if one is served upon a company, that company will have to turn over the information requested. However, if a company is outside the jurisdiction of the courts passing down such decisions, a subpoena based upon a lesser standard may still be enough to compel disclosure.

While these six cases are currently the state of the law on disclosure of cell site tracking information, the increased national attention being paid to the conflict between privacy and technological progress ensures that rulings in other districts will follow quickly. We are tracking this issue very closely and are available for any assistance or guidance you may require.


1. The Federal Trade Commission has instituted a requirement that service providers make this tracing capability 95% accurate within 150 meters and 67% accurate within 50 meters.

2. Application for a Pen Register and Trap and Trace Device and Authorizing Release of Subscriber Information and/or Cell Site Information, 396 F.Supp.2d 294 (E.D.N.Y. 2005) (“E.D.N.Y. Decision”); Application for Pen Register and Trap/Trace Device with Cell Site Location, 396 F.Supp.2d 747 (S.D.Texas 2005) (“Texas Decision”); In re Application of the United States for an Order Authorizing the Installation and Use of a Pen Register and a Caller Identification System on Telephone Numbers (Sealed) and Production of Real Time Cell Site Information, 2005 WL 3160860 (D. Md. Nov. 29, 2005) (“Maryland Decision”); In re Application of the United States of America for an Order for Disclosure of Telecommunications Records and Authorizing the Use of a Pen Register and Trap and Trace, 2005 WL 3471754 (S.D.N.Y. Dec. 20, 2005) (“S.D.N.Y. Decision”); In the Matter of the Application of the United States of America for an Order Authorizing the Release of Prospective Cell Site Information, 2006 WL 41229 (D.D.C. Jan. 6, 2006) (“DC Decision”); In Matter of Application of U.S. For an Order Authorizing the Disclosure of Prospective Cell Site Information, 2006 WL 243017 (E.D.Wis. Jan 17, 2006) (“Wisconsin Decision”).

3. The District of Columbia’s discussion of probable cause as a standard may be considered dicta; the predominant ruling was a denial of the government’s request for cell site information. Judge Callahan of the Eastern District of Wisconsin denied the government’s application for an order to obtain cell site information, but declined to rule on whether a request based upon probable cause pursuant to Federal Criminal Rules of Procedure Rule 41 would be sufficient to grant a search warrant. See Wisconsin Decision at *1.

4. See S.D.N.Y. Decision.

5. 18 U.S.C. § 2703(c).

6. 18 U.S.C. § 2703(d).

7. See Maryland Decision at *4-*5.

8. 18 U.S.C. § 3122(b)(2).

9. Pub.L. No. 107-56, 115 Stat. 272 (2001).

10. The PATRIOT Act adds to the definition of “pen register” “‘signaling information’ transmitted by the subject telephone itself or the ‘facility from which a wire or electronic communication is transmitted.'”

11. Pub.L. No. 103-313, 108 Sta. 4279 (1994).

12. 47 U.S.C. § 1002(a)(2).

13. See Maryland Decision at *6-*7.

14. See Tresa Baldas, “Feds’ Cell Phone Tracking Divides the Courts” The National Law Journal, January 19, 2006. Found online at:

15. Maryland Decision at *7 n.12, also noting that the Judges in the Texas and E.D.N.Y. Decisions also declined to make a Fourth Amendment ruling.

16. S.D.N.Y. Decision at *2.

17. S.D.N.Y. Decision at *5.

18. DC Decision at *6.

About Daniel R. Sovocool (1 Articles)

A primary focus of Daniel Sovocool’s practice is advising national clients on a variety of insurance (and self-insurance), regulatory and business matters, particularly in the area of workers’ compensation.