Skip to Content
Call Us Today! 888-258-8049

U.S. Supreme Court: Warrant Required for Historical Cell Phone Location Information


The Fourth Amendment to the United States Constitution protects citizens against the unreasonable search and/or seizure of their homes, vehicles, offices, and even conversations. If a search into a constitutionally protected domain is to be lawful, the government must first obtain a warrant, supported by probable cause, from a neutral and detached magistrate (or judge). In analyzing the applicability of Fourth Amendment protections to a particular search, the court will determine whether the person had a "legitimate expectation of privacy" in the sphere that was searched or seized.

There are certain exceptions to the warrant requirement that will justify a search where a warrant is not first obtained. It is generally recognized, for example, that law enforcement can search an individual, and the area within his or her immediate reach, incident to a lawful arrest. An officer may search an automobile without a warrant if the officer has probable cause to believe that contraband will be found inside. A person's home may be searched if the officer has probable cause to believe that a crime is occurring inside, or that contraband will be located inside, under circumstances that are sufficiently "exigent". There are a number of other instances wherein a search or seizure may be justified in the absence of a warrant. For more information, see our previous post entitled "Search & Seizure in Florida: An Overview".

If there is no warrant, and no valid exception to the warrant requirement, evidence seized by government agents is suppressible. Where evidence is suppressed, it cannot be used against the accused person at trial. In many instances, this means that the state (or the federal government) cannot proceed with prosecution.

In the case of United States v. Carpenter, the appellant was prosecuted in a Michigan District Court for six counts of robbery and six additional counts of carrying a firearm during a federal crime of violence. Prosecutors petitioned the court for an order authorizing them to obtain the appellant's cell phone location data, under the "Stored Information Act", in an apparent attempt to prove that he was at the location of the robberies as they were occurring. All that is required to obtain records under the provisions of the Stored Information Act is a showing, by the government, that there are "reasonable grounds" to believe that the records are "relevant and material to an ongoing investigation" - a far cry from the more stringent probable cause standard required for the issuance of a search warrant.

The Court granted the motion, and the government thereafter obtained 12,898 location points cataloging the appellant's movements over 127 days, for an average of 101 data points per day. As you are likely aware, a person's cell phone will "ping" off of cell towers in the vicinity, which generates a time stamped record. These records are known as cell site location information and are maintained by the various wireless carriers. The time frame involved here is quite extensive - 127 days is by no means fleeting. As the Supreme Court seemed to imply in its opinion, the longer the time frame involved, the more that privacy concerns will be implicated.

In Carpenter, the appellant filed a motion to suppress (in District Court) arguing that the government's seizure of the records, without first obtaining a warrant, supported by probable cause, violated the Fourth Amendment. The court denied the motion and the government introduced the records at trial to show that the appellant was at four of the robbery locations at the time of their commission. The appellant was convicted and filed an appeal with the Sixth Circuit Court of Appeals. The higher court affirmed the ruling, holding that the appellant lacked a reasonable expectation of privacy in the location information of his cell phone because he had shared that information with his wireless carriers (this is known as the third party doctrine, which stems from the notion that an individual has a reduced expectation of privacy in information knowingly shared with another). In a landmark decision reached just yesterday, the United States Supreme Court held that a person has an expectation of privacy in his or her physical movements and whereabouts, and in cell site information data maintained by wireless carriers. Thus, if the government is to obtain that information for the purpose of prosecution, a search warrant must first be obtained.

In his opinion, Chief Justice Roberts stated that "requests for cell-site records lie at the intersection of two lines of cases, both of which inform our understanding of the privacy interests at stake". The first set of cases address an individual's expectation of privacy in his or her physical location, and the second relates to a person's expectation of privacy in information shared with others.

With regard to physical location, Chief Justice Roberts cited to precedent setting cases involving GPS monitoring, wherein the Court had held that "longer term GPS monitoring in investigations of most offenses impinges on expectations of privacy" even where the person's location was disclosed to the public at large by virtue of traveling on public roadways. Note the phrase "longer term" in the prior case holding; once again the court seems to imply that the longer the surveillance goes on, the less likely it is that evidence obtained in conjunction therewith will be admissible in the absence of a valid search warrant supported by probable cause.

With regard to information shared with third parties, and how that affects a person's expectation of privacy in such information, Chief Justice Roberts made reference to prior cases involving bank records wherein it was held that that no expectation of privacy existed: because the record of deposits, withdrawals, and other information was shared by the account holder with the bank itself, the "third party doctrine" applied and a search warrant was not necessary to obtain those records. He noted, however, that cell phone location records were different. Given their "unique nature", the fact that they are held by a third party (e.g. the wireless carrier), does not in and of itself overcome the user's claim to Fourth Amendment protection. There is, it seems, something much more invasive about tracking a person's every move for many months, to include every place visited and the time each place was visited, than a record of banking transactions. The majority held that "an individual maintains a legitimate expectation of privacy in the record of his physical movements as captured through cell site location information" even though that information is automatically shared with the wireless provider.

The Court was careful to point out that yesterday's decision was a narrow one. It made clear that is was not expressing a view on real time cell site location data, or "tower dumps" which it described as "a download of information on all devices that are connected to a particular cell site during a particular interval". What invokes Fourth Amendment protections in these cases is the chronic, persistent monitoring of person's movements over time, which, in the case of Carpenter, was 127 days. Real-time monitoring does not, apparently, invoke the same privacy concerns as historical location data recorded over longer periods.

We live in an ever-changing world. Technological advances are being made at staggeringly narrow intervals. Yesterday's ruling is yet another example of how our jurisprudence must change and adapt to these advances at a similar pace. These types of issues will continue to be raised and litigated. And, as always, I will keep you posted.