Does Law Enforcement Need a Warrant to Obtain Cell-Site Location Data?

December 11, 2017
Jay Kesan

Jay Kesan

University of Illinois College of Law

When you make or receive a phone call or text message with your cellular phone, your service provider stores information about which cell tower transmitted this signal, thus revealing the general area where you were located when that transmission occurred.  

Courts have been disagreeing for years about whether this historic cell-site location data gathered by your cellphone service provider can be obtained without a warrant.  On November 29th, the U.S. Supreme Court heard oral arguments in U.S. v. Timothy Carpenter to resolve this issue.  That case involved a string of robberies.  The defendant’s physical proximity to the robberies, as shown by cell site data, was used as circumstantial evidence against him.  Should the police have obtained a warrant before they collected information about the whereabouts of Mr. Carpenter’s phone and by extension, Mr. Carpenter himself? 

With respect to the warrant requirement and the Fourth Amendment in the U.S. Constitution, one issue that arises is the third party doctrine.  In the past, the Supreme Court has stated that people do not have a reasonable expectation of privacy in records voluntarily disclosed to a third party, and therefore, a warrant is not required.  But when this rule was formulated, it was in the context of people actively giving their records to someone else, like handing over your financial records to your tax advisor.  There is no individual who is being handed your cell site location data.  That information is automatically collected and stored until an actual person needs to interact with it.  

The Stored Communications Act, or the SCA, is the federal statute that determines how law enforcement can obtain stored digital information.  It was enacted in the 1980s to address how the Fourth Amendment applies to digital information.  Under this law, non-content information, like cellphone location data, can be obtained without a warrant.  But obtaining such location data amounts to retroactive surveillance of the past that was impossible when the SCA was enacted.

Does it also matter for how long cell site location data is being sought?  In the Carpenter case, such data was sought for 127 days.  The Massachusetts Supreme Judicial Court has ruled that if the police are asking for more than 6 hours of historic cell site location data, a warrant is required.  

In another consideration, should it matter whether cell site location data is related to a call or whether cell site registration data is being sought?  In the first case, a user’s location is provided only during phone calls, whereas, in the second case, registration data is created every few seconds when a cellphone pings a nearby cell tower.  Since the registration data is more granular, should only such data require a warrant?

How the Supreme Court rules could have significant implications for investigations and privacy rights.  Requiring a warrant for cell site location data could make investigations more difficult and costly.  If the Supreme Court holds that collecting historic cell site location data is not a search, then law enforcement will not need to show probable cause before examining such data.  To some people, privacy is not important unless there is something to hide.  But even those people may be bothered to learn that they are the target of government surveillance.  Once the government has such data, there is a concern about how this data might be used.  Although law enforcement does not routinely monitor citizens constantly, NSA surveillance programs have made many Americans skeptical. 

Requiring a warrant will incentivize law enforcement to stay within the law and preserve individual privacy.  It may also be viewed favorably at a time when Americans are distrustful of government surveillance.  The Supreme Court’s decision is expected by next June.