Cellphone Privacy and Warrant Requirements

Most electronic devices are internet-connected, GPS-enabled smartphones. They track our movements, online purchases, personal relationships, and more. But while we know — or should know — of such exposure, we still have certain expectations of privacy under the law.

According to most estimates, there are more mobile phones than people in the United States. This article explores the basics of cellphone privacy concerning the following:

  • The Fourth Amendment right against unreasonable search and seizure
  • The third-party doctrine
  • The changing nature of search warrant requirements for cellphone records

But where is the line drawn regarding cellphone privacy and warrant requirements? Can the government collect what we share, even if we are unaware of what we share? Or are there limits?

Fourth Amendment Basics

The meaning and scope of the Fourth Amendment to the U.S. Constitution have become increasingly complex. However, its fundamental purpose remains to protect people against government intrusion.

Law enforcement cannot perform a search without legal justification. Police officers typically need a search warrant. They must show probable cause for a judge to issue a warrant. A search warrant is a court order indicating the parameters of a search.

Unreasonable searches and seizures violate your constitutional rights. If police search your house without a valid warrant, a judge will likely exclude any seized evidence from your criminal case. However, law enforcement officers are sometimes justified in performing warrantless searches.

Certain things that police observe in the open or legally obtain from third parties are not considered a "search." Therefore, these searches do not require a warrant. For instance, an FBI agent who overhears a suspect sharing incriminating information while talking on their cellphone in public can use that information as evidence. The FBI cannot, however, wiretap that person's phone without a valid warrant.

Cellphones often raise much more complicated Fourth Amendment issues than searches involving other property. For example, consider the difference between the data you share and data shared beyond your control.

Cellphone Privacy and the Third-Party Doctrine

The "third-party doctrine" states that individuals have a reduced expectation of privacy regarding information knowingly shared with a third party, including cellphone companies. The Fourth Amendment does not protect such information. Therefore, police do not need a warrant to access it legally.

The U.S. Supreme Court established the third-party doctrine before the first cellphones were made available to consumers. In the case of Smith v. Maryland (1979), the Supreme Court held that "a person has no legitimate expectation of privacy in information he voluntarily turns over to third parties." The phone company was already in possession of numbers dialed in that case.

You willingly expose yourself every day with your cellphone. You do so by actively making phone calls, using location data, and saving data to cloud-based servers. But since you share an enormous amount of data daily, often unconsciously, it is not always clear what you share or when. This gray area on phone records has generated plenty of debate. The ever-increasing sophistication of digital devices further complicates it.

Justice Sonia Sotomayor addressed this in a 2012 case (United States v. Jones) that involved GPS tracking. She questioned whether all data subject to the third-party doctrine should be exempted from Fourth Amendment protection. She wrote:

"This approach is ill suited to the digital age, in which people reveal a great deal of information about themselves to third parties in the course of carrying out mundane tasks."

Warrant Requirements for Cellphone Data

Despite the private information that cellphone data may reveal to police, these are services you choose to use. But while the choice to use a cellphone or smartphone is voluntary, the simple act of turning on your phone does not result in the forfeiture of your Fourth Amendment rights. Several court decisions have clarified your Fourth Amendment rights regarding cellphone data.

In Carpenter v. United States (2018), the Supreme Court ruled that cell site location information (CSLI) is not subject to the third-party doctrine. The justices made this ruling despite users sharing CSLI with cellphone service providers.

CSLI refers to the data generated each time a cellphone connects to a nearby tower. Taken as a whole, this data can track a person's location data with some degree of accuracy. It's still less definitive than GPS data. In the Carpenter opinion, Chief Justice John Roberts (partially quoting another case) noted:

First, cellphones and the services they provide are "such a pervasive and insistent part of daily life" that carrying one is indispensable to participation in modern society. Second, a cellphone logs a cell-site record [CSLI data] by dint of its operation, without any affirmative act on the user's part beyond powering up.

In Riley v. California (2014), a police officer conducted a search incident to arrest. Law enforcement seized the plaintiff's cellphone. Police searched the phone without a warrant. The suspect argued that police violated his constitutional rights by searching his phone without a warrant. The Supreme Court's ruling in Riley requires police to obtain a warrant before viewing the contents of a cellphone seized after an arrest. The Supreme Court reversed the lower court, the California Court of Appeal, as it related to warrant requirements.

As new technology emerges, the nature of the third-party doctrine likely will be revisited. As technology changes, legal questions about warrant requirements for cellphone data will surely be raised.

Concerned About Cellphone Privacy? Contact an Attorney

Knowing and protecting your privacy interests is crucial if law enforcement charges you with a crime. If you believe police have violated your Fourth Amendment rights, you should consider calling a lawyer. A criminal defense lawyer can help you with the following:

  • Criminal law in general
  • Explaining your reasonable expectation of privacy rights and privacy protections
  • Law enforcement's ability to seize evidence of a crime
  • Legal advice on law enforcement's search of a cellphone
  • Court rulings regarding cellphone privacy
  • Cellphone users' rights

Get peace of mind and protect your privacy rights by speaking with a local criminal defense attorney.

Was this helpful?

Can I Solve This on My Own or Do I Need an Attorney?

  • Complex criminal defense situations usually require a lawyer
  • Defense attorneys can help protect your rights
  • A lawyer can seek to reduce or eliminate criminal penalties

Get tailored advice and ask your legal questions. Many attorneys offer free consultations.


If you need an attorney, find one right now.