David L. Riley was pulled over in San Diego in 2009 for having an expired vehicle registration. The police found loaded guns in his car.  After seizing a cell phone from Riley's pants pockets, the police found text messages and words in his contact list associated with the "Bloods" street gang.  At the police department about two hours after his arrest, a gang detective searched the phone again and found videos and photographs linking Riley to gang and other criminal activity, including a shooting.  Riley was later convicted of attempted murder and sentenced to 15 years to life in prison. The California Court of Appeal said that neither search of Riley required a search warrant.

Brima Wurie was arrested and taken to a police station where police officers seized two cell phones from Wurie.  The cell phone at issue was a flip phone, an older type of cell phone that has fewer features than a smart phone.  The police searched the flip phone and found identifying information on the phone that led them to an apartment that police searched after obtaining a warrant-seizing drugs, cash, ammunition, and firearms.  Wurie was charged with gun and drug crimes, but the First Circuit Court of Appeals excluded the evidence found on Wurie's flip phone, finding that the search of Wurie's flip phone violated the Fourth Amendment ban against unreasonable search and seizures.

The U.S. Supreme Court reviewed both decisions and analyzed whether it is reasonable for the police to conduct a warrantless search of cell phones incident to a lawful arrest.  The law previously recognized that certain searches are exempt from the search warrant requirement.  To determine whether the police can conduct a search without first getting a warrant, the Court is to balance the degree to which the search intrudes upon an individual's privacy with the degree to which it is needed to promote legitimate governmental interests. 

The Court analyzed the privacy rights of individuals in the data on their cell phones.  Chief Justice Roberts wrote that cell phones "…are now such a pervasive and insistent part of daily life that the proverbial visitor from Mars might conclude they were an important feature of human anatomy."  The Court also acknowledged the vast amount of private data that can be stored on cell phones.

The Court balanced the privacy rights of individuals against the police's interest in conducting searches of cell phones without first securing a warrant.  Traditionally, harm to police officers and a risk of destruction of evidence have served as rationales for allowing searches of physical objects without first seeking a warrant.  The Court found that harm to police officers, and a risk of destruction of evidence, are not risks associated with searching the digital content on a cell phone.  Digital data on a cell phone cannot itself be used as a weapon to harm a police officer or to effectuate the escape of the arrestee.  Police may still search a phone's physical aspects to make sure that the phone itself will not be used as a weapon, but since the data on the phone does not endanger anyone, the data cannot be searched without a warrant. Given the "vast quantities of information literally in the hands of individuals," the privacy interests of the individual outweigh the interests of the government in conducting a search of a cell phone without a warrant. 

Regarding the destruction of evidence, the Court stated that such concerns are remote, and that there are reasonable methods police may use to prevent the destruction of evidence on cell phones.  For example, remote wiping of a cell phone can be prevented by police turning the phone off or removing the battery.  And encryption of data on the phone may be avoided by leaving the phone on and placing it in an enclosure that isolates the cell phone from radio waves.  The Court acknowledged that if the police can demonstrate that they still have concerns about the loss of evidence on a cell phone, the police may be able to rely on exigent circumstances to search the cell phone without first obtaining a warrant.  For example, if there is evidence to suggest that an arrestee's cell phone will be the target of an imminent remote-wipe, the police may be able to rely on exigent circumstances to conduct a warrantless search.

The Court unanimously held that police officers must generally secure a search warrant before conducting a search of a cell phone because the governmental interests traditionally associated with a physical search are absent in the context of searching cell phones.  Justice Roberts acknowledged that the Court's decision "…will have an impact on the ability of law enforcement to combat crime."  However, an individual's privacy interest in the vast amount of personal information that can be stored on cell phones outweighed the government's interests in combatting crime.  Justice Roberts stated that: "Cell phones have become important tools in facilitating coordination and communication among members of criminal enterprises, and can provide valuable incriminating information about dangerous criminals.  Privacy comes at a cost."  He then clarified that the data on cell phones is not exempt from any search at all, but that generally police will need to obtain a search warrant to conduct searches of cell phone data.

NOTE:

 In one sense, the Court's decision in this case has limited application in the employment context because it analyzed the legality of searching the cell phone of a lawfully-arrested individual, not an employee.  However, the Court's discussion of smart phones, including their prevalence and the vast amount of private information that can be stored on them, will likely have a broad and long-lasting effect on privacy law in general.  A "significant majority of American adults" own smart phones, which can reveal, among other things, where an individual has been, who he has talked to, and what Internet searches he has performed over the past few months.  In City of Ontario v. Quon (2010) 130 S.Ct. 2619, the Supreme Court held that the City's review of a transcript of an employee's text message did not violate the Fourth Amendment.  However, in that case, the City issued certain employees alphanumeric pagers capable of sending and receiving text messages, and told the employees that text messages would be subject to auditing.  In light of how much more information a smart phone can reveal about someone than an alphanumeric pager, expect courts to require employers that issue smart phones to maintain policies clearly and unmistakably notifying employees that they do not have a reasonable expectation of privacy in the phones or the electronic communications sent to and from the phones. 

Riley v. California (2014) 134 S.Ct. 2473.