US Supreme Court holds warrant is required for accessing location data

Carpenter v United States, S. Ct.  (22 June 2018)


The US Supreme Court held that a warrant is required for police to access cell site location information (CSLI) from a cell phone company under the Fourth Amendment of the US Constitution. Chief Justice Roberts for the majority stated that the Court would "decline to grant the state unrestricted access to a wireless carrier's database of physical location information".

The facts

In 2011, four men were arrested in connection with several armed robberies of Radio Shack and T-Mobile stores in the USA. Police obtained court orders concerning the perpetrators and their co-conspirators, to produce transactional records from the phone numbers of those involved. One of the offenders, Timothy Carpenter, was convicted and sentenced to 116 years in prison for his part in the burglaries, using CSLI evidence that placed Mr Carpenter near the robberies at the relevant times.

Following various unsuccessful appeals under the Fourth Amendment, which protects people from unreasonable searches and seizures by government, the Supreme Court agreed to hear MrCarpenter's appeal.

The key legal principles

Quoting the Supreme Court’s ruling in Camara v Municipal Court of City and County of San Francisco, Chief Justice Roberts posited that the basic purpose of the Fourth Amendment “is to safeguard the privacy and security of individuals against arbitrary invasions by governmental officials.”

Of further relevance, is the more contemporary case of United States v Jones (2012) which recognised that surveillance can impinge on expectations of privacy. In this case, it was held that longer term GPS monitoring in investigations of most offences can infringe upon privacy rights.

In Riley v California (2014) the Court recognised the “immense storage capacity” of modern cell phones, and held that police officers must generally obtain a warrant before searching the contents of a phone. The decision reflects a willingness of the Court to modernize its approach to interpreting the rights enshrined in the Fourth Amendment.

One key exception exists in the Third Party Doctrine, in which information provided voluntarily to a third party is not protected by the Fourth Amendment. As such, no warrant is required to obtain it.

Majority Opinion

In the majority opinion of the Court, Chief Justice Roberts considered that CSLI does not “fit neatly under existing precedents,” and that it instead lies at the “intersection of two lines of cases”, the first addressing geolocation, and the second addressing the third-party doctrine.

In considering the legal precedent before him, Chief Justice Roberts distinguished United States v Knotts (1983) (a geolocation case) in which the court held that a warrant was not required to follow a beeper placed in the suspect's car, from Jones, in which the Court held a warrant was required for the placement of a GPS device.

Chief Justice Roberts then moved to consider the third party doctrine, addressing two cases: US v Miller (1976) and Smith v Maryland (1979). Both cases found that no expectation of privacy existed in relation to bank records and phone company records respectively. Focusing upon Smith, Chief Justice Roberts noted that when Smith placed a call, he voluntarily conveyed the dialed numbers to the phone company by "expos[ing] that information to its equipment in the ordinary course of business". The Court held that the defendant assumed the risk that the company's records would be provided to the police.

Following this, the Chief Justice turned to the key issue in the case – namely, whether a warrant is required to access CSLI. Highlighting the potential privacy impact of CSLI, he noted "much like GPS tracking of a vehicle, cell phone location information is detailed, encyclopedic, and effortlessly compiled.” At the same time, he observed the additional fact that the individual continuously reveals his location to his wireless carrier. This implicates the third party doctrine.

Ultimately, the majority declined to extend the third party doctrine considered in Smith and Miller.  It found that, given the unique nature of cellphone location records, the fact that the information is held by a third party does not by itself overcome the user’s claim to Fourth Amendment protection. The location information obtained from Carpenter's wireless carriers was the product of a search.

Dissenting Opinions

In a dissenting opinion, Justice Kennedy together with Justices Thomas and Alito, maintained that "cell-site records, however, are no different from the many other kinds of business records the Government has a lawful right to obtain by compulsory process." The dissenting justices called the distinction illogical and believed it "frustrate[d] principled application of the Fourth Amendment."


The constitutional protection of privacy of individuals from unwarranted government intrusion is important, although much remains to be resolved as to the application of the protection to new technologies. This may not be aided by the decision itself, which is lengthy and apt for interpretation (or misinterpretation) by lower courts, which may lead to confusion including for law enforcement.

It is important to consider that the information contained within mobile phones (let alone future technology and information gathering devices) is more than just phone call records and bank transaction histories – it gives intimate access to our personal lives. This includes where and what we eat, who we date, our everyday movements and our habits.

In the USA, it remains to be seen how far the Fourth Amendment will go in protecting such personal information from disclosure to government. In Australia however, where there is no constitutional or common law right to privacy, and only limited statutory privacy rights, there is very little citizens can do to challenge such decisions. This is a particular concern given the enormous body of national security legislation that has passed since 11 September 2001, including the decryption law that passed late last year.  

The full text for the decision can be found here.

Stephanie Burn is a Senior Associate at Allens.