An arrest gives police powers they ordinarily would not have.
Officers can take physical custody of the person being arrested. They can seize items being carried. And under a long-established exception to the Fourth Amendment's warrant requirement, police generally can search the arrested person and the area within that person's immediate control.
For generations, that rule applied to things found in pockets: wallets, papers, address books, cigarette packages and other physical objects.
Then nearly everyone began carrying something very different.
A smartphone.
A modern phone can contain years of photographs, conversations, emails, financial information, browsing history, medical information, location-related data and access to online accounts.
So what happens when police arrest someone and find a phone in a pocket?
Can they simply open it and start looking?
The Supreme Court confronted that question in 2014.
Its answer changed the rules for digital privacy in America.
The Arrest Began With a Traffic Stop
The case was Riley v. California.
David Riley was stopped by police in San Diego in 2009 for a traffic violation.
The stop eventually led to his arrest on weapons charges.
During the arrest, an officer seized a cell phone from Riley's pants pocket.
The police didn't stop at taking possession of the device.
An officer accessed information stored on the phone. Later, a detective examined its digital contents more extensively.
Police discovered photographs, videos and other information they believed connected Riley to gang activity and a shooting.
Some of that information was ultimately used against him.
Riley argued that searching the contents of his phone without a warrant violated the Fourth Amendment.
The dispute eventually reached the United States Supreme Court.
Police Have Long Been Allowed to Search Someone They Arrest
At first glance, the government's position had substantial support in longstanding law.
The Fourth Amendment generally requires police to obtain a warrant before conducting a search, but there are important exceptions.
One of them is the search-incident-to-arrest doctrine.
When police lawfully arrest someone, officers generally may search the person without first obtaining a separate search warrant.
There are practical reasons for the rule.
An arrested person might possess a weapon.
Evidence might be concealed or destroyed.
Police therefore need some ability to secure the person and the immediate surroundings during an arrest.
For physical objects, that principle had existed long before smartphones appeared.
The difficult question was whether the same rule should allow police to search everything stored inside a phone merely because the device happened to be in someone's pocket.
The Supreme Court Said a Phone Is Different
The Supreme Court decided Riley v. California on June 25, 2014.
The Court held that police generally may not search the digital information contained on a cell phone seized from an arrested person without first obtaining a warrant.
That distinction is crucial.
Police can seize the phone.
That does not mean they automatically can search its digital contents.
The Court recognized that treating a smartphone like an ordinary physical object ignored what the device actually contains.
A wallet has physical limits.
A phone can provide access to enormous quantities of information.
It can contain thousands of photographs.
Years of messages.
Internet browsing history.
Location-related information.
Applications revealing interests and activities.
Financial records.
Personal communications.
And information that may reveal far more about someone's private life than officers could ever have found by searching a pocket before the digital age.
The Physical Phone and the Information Inside It Are Different Things
This distinction can initially seem strange.
If police can lawfully take a phone from an arrested person's pocket, why can't they look through it?
Because possession of the physical object and examination of its digital information raise different privacy concerns.
Imagine police arrest someone carrying a key.
Police can take possession of the key.
That does not necessarily give them unlimited authority to use it to open every place the key might unlock.
A smartphone creates an even more complicated version of that problem.
The physical device might fit in a hand.
The information accessible through it can encompass an enormous portion of a person's life.
The Supreme Court therefore rejected the idea that the traditional authority to search physical items found during an arrest automatically justified a warrantless search of digital information stored on a phone.
What About Officer Safety?
One traditional justification for searches incident to arrest is officer safety.
An arrested person might be carrying a weapon.
That concern makes obvious sense when officers search clothing or containers within immediate reach.
But digital information stored on a phone cannot itself be used as a physical weapon against an officer.
The phone as a physical object still can be examined for physical threats.
The Court's decision concerned the information stored inside the device.
That difference weakened one of the traditional reasons for allowing an immediate warrantless search.
What About Destroying Evidence?
The government also raised concerns about evidence being destroyed.
Digital information can potentially be deleted remotely.
A phone might also automatically lock or encrypt information.
Those concerns are real, but the Supreme Court concluded that they did not justify a categorical rule permitting warrantless searches of every arrested person's phone.
Police have other ways to secure a device while seeking a warrant.
And when a genuine emergency exists, another exception to the warrant requirement may apply.
The Fourth Amendment has never required police to ignore an immediate emergency merely because officers do not yet possess a warrant.
But an emergency exception and a blanket rule are very different things.
Riley Did Not Make Phones Untouchable
The Riley decision is sometimes simplified into the statement that police cannot search phones.
That goes too far.
The Court's rule is generally about searching a phone without a warrant merely because its owner has been arrested.
Police can seek a search warrant.
If investigators establish probable cause and a judge issues an appropriate warrant, the phone can potentially be searched within the lawful scope of that authorization.
Other recognized exceptions to the warrant requirement may also apply in particular circumstances.
The Supreme Court itself emphasized the straightforward practical consequence of its decision: when officers want to search the digital information on a seized phone, they generally should obtain a warrant.
A Warrant Is Not Unlimited Permission
Obtaining a warrant does not necessarily mean investigators receive unlimited authority to examine every piece of digital information associated with a person.
The Fourth Amendment requires warrants to particularly describe the place to be searched and the persons or things to be seized.
Applying that requirement to smartphones can be complicated.
A single phone may contain many different categories of information.
Suppose investigators are looking for evidence concerning a financial fraud committed during a particular month.
The phone might simultaneously contain years of family photographs, medical communications and unrelated personal conversations.
Courts increasingly must confront questions about how traditional warrant requirements apply to devices containing enormous quantities of mixed information.
The basic constitutional principles are old.
The container is new.
Your Passcode Creates a Different Legal Question
Searching a phone is not always as simple as obtaining the device.
The phone may be locked.
That creates a separate question:
Can the government force someone to unlock it?
The answer can become complicated because unlocking a device can implicate legal principles beyond the Fourth Amendment.
The Fifth Amendment protects against compelled self-incrimination.
Courts have wrestled with whether forcing someone to reveal a memorized passcode is legally different from requiring the use of a fingerprint or facial recognition.
Those issues have generated differing decisions depending on the facts, jurisdiction and method of unlocking the device.
They are separate from the central rule in Riley.
A warrant authorizing a search and the government's ability to compel someone to help unlock a device are not necessarily the same legal question.
What If the Phone Is Already Unlocked?
An unlocked phone does not automatically eliminate Fourth Amendment protections.
The central issue in Riley was not whether the device happened to require a password.
It was whether the traditional search-incident-to-arrest exception automatically authorized police to inspect digital information.
The Supreme Court said it generally did not.
A person does not ordinarily lose the constitutional protection recognized in Riley simply because a phone happened to be unlocked when police obtained it.
Consent Can Change Everything
There is another major exception to the warrant requirement: consent.
A person can voluntarily permit police to conduct a search that might otherwise require a warrant.
That principle applies to phones as well.
If someone voluntarily gives officers permission to examine a device, the legal analysis can be very different.
But consent itself can become disputed.
What exactly did the person agree to?
Was permission limited to looking at one photograph?
Did the person agree to a search of messages?
Did the consent extend to an entire device?
Was consent actually voluntary?
A statement as simple as “you can look” can become significant when a later dispute arises over what police were authorized to examine.
The Phone May Lead to Evidence Somewhere Else
A phone can also become important even when investigators are interested in evidence outside the device.
That happened in the companion case decided with Riley, United States v. Wurie.
Police arrested Brima Wurie after observing what they believed was a drug transaction.
At the police station, officers examined information on a phone seized from him.
Information from the phone helped lead police to an apartment.
Police subsequently obtained a warrant to search the apartment and discovered drugs, a firearm, ammunition and cash.
The Supreme Court considered Wurie's case together with Riley's and applied the same fundamental rule regarding warrantless searches of digital information on phones seized during arrest.
The case illustrates why a phone search can matter far beyond the device itself.
Information found on a phone can direct investigators toward other people, locations and evidence.
Modern Phones Changed the Scale of a Search
The importance of Riley becomes clearer when comparing a smartphone with the objects people carried before smartphones existed.
Imagine searching someone's wallet.
Police might find identification, several cards, receipts and perhaps a few pieces of paper.
Now imagine searching a phone.
The device might reveal who the person communicates with.
Where the person has traveled.
What the person photographs.
What the person reads.
What the person searches for.
What applications the person uses.
What appointments appear on a calendar.
What financial information is accessible.
What conversations occurred months or years earlier.
The difference is not merely that a smartphone holds more items.
It can reveal relationships among those items.
Photographs, communications, locations and dates can combine to produce a detailed picture of someone's activities and associations.
That scale helped explain why the Supreme Court refused to treat a smartphone like an ordinary object discovered in a pocket.
Cloud Computing Makes the Boundary Even Stranger
There is another reason the old physical-container analogy became difficult.
Not everything visible through a phone necessarily resides physically on the phone.
Modern devices connect to cloud services and remote servers.
A person can open a phone and immediately access photographs, documents, email and other information physically stored somewhere else.
That means searching a small object can potentially expose information located far beyond the device itself.
The Supreme Court noted the complications created by cloud computing when considering how digital searches differ from traditional physical searches.
The physical boundaries that once naturally limited a search no longer work the same way.
The Rule Applies Because of What Phones Have Become
Perhaps the most enduring aspect of Riley is that the Supreme Court did not treat technological change as legally irrelevant.
The search-incident-to-arrest doctrine existed before smartphones.
The Fourth Amendment existed centuries before smartphones.
But the Court considered what modern phones actually are and what they reveal.
That makes Riley important beyond the particular devices people carried in 2014.
Phones have continued to become more capable.
They increasingly connect with vehicles, homes, watches, financial accounts, health applications and cloud services.
The precise technology changes.
The underlying problem remains.
How should constitutional rules developed in a physical world apply when a tiny device can provide access to an enormous collection of personal information?
An Arrest Does Not Erase Digital Privacy
Being arrested dramatically changes a person's legal situation.
Police can take custody of the person.
They can seize property.
They can conduct searches that would not have been permitted moments earlier.
But the Supreme Court drew an important boundary around the digital contents of a phone.
The government does not ordinarily receive automatic access to someone's digital life simply because the phone happened to be in a pocket at the moment of arrest.
The police can secure the device.
They can preserve it.
They can seek judicial authorization to search it.
And when a genuine emergency or another recognized exception exists, different rules may apply.
But the ordinary arrest itself is not enough.
That principle is what made Riley v. California one of the defining privacy decisions of the smartphone era.
The technology inside our pockets changed enormously.
The Court concluded that the constitutional analysis had to recognize that change too.