WASHINGTON — The Supreme Court, offering a sweeping endorsement of Americans’ right to digital privacy, unanimously declared Wednesday that police must obtain a warrant before searching a suspect’s cellphone.
The justices, in a ruling that has its roots in a case from South Boston, said the constitutional protections against undue search and seizure must keep pace with the technology that now allows thousands of details about citizens’ lives to be stuffed onto a ubiquitous device no bigger than a wallet.
“Our answer to the question of what police must do before searching a cellphone seized incident to an arrest is accordingly simple — get a warrant,” Chief Justice John G. Roberts Jr. wrote in the main opinion for eight of the nine justices.
The decision applies to a pair of cases — one involving a drug dealer suspected of selling crack cocaine in South Boston, and the other a California gang member — that raised the question of whether police could pry the contents of a cellphone in the same way they could search a suspect’s pockets or handbag following an arrest.
Cellphones today are not just “another technological convenience,” Roberts wrote in the ruling, which displayed rare unanimity on a major issue. “With all they contain and all they may reveal, they hold for many Americans the privacies of life. The fact that technology now allows an individual to carry such information in his hand does not make the information any less worthy of the protection for which the Founders fought.”
Some privacy advocates said the court planted a flag firmly on the side of privacy and the rights of the individual against the state.
“This is an enormously important decision that says not just in this case, but potentially in many others as well, that digital is different,” said Matthew Segal, legal director of the ACLU Foundation of Massachusetts. “Time and again, the government has argued that decades-old cases involving physical items could be easily applied to 21st-century cases involving digital items. In this decision, a unanimous court is saying that not only is that argument wrong, it’s basically absurd.”
Police organizations said Wednesday that they were disappointed by the ruling, maintaining it throws up an obstacle to obtaining evidence of crimes.
“It’s fair to say that evidence will go missing,” said Bill Johnson, executive director of the National Association of Police Organizations, based in Alexandria, Va. “That’s the consequence of this.”
James Machado, executive director of the Massachusetts Police Association, said, however, that he does not think it will be an insurmountable hurdle to obtain a search warrant, especially in drug arrests.
“It just adds to the length of the investigation,” he said.
In 2007, police arrested Brima Wurie in a South Boston parking lot for allegedly selling crack cocaine from his car. Police were able to find where he lived following a search of his cellphone log. They were then able to find other evidence used to convict him of drug and gun crimes.
Wurie was sentenced to more than 21 years in prison in US District Court. But the First Circuit threw out his conviction last year, ruling that the warrantless search of Wurie’s cellphone was unconstitutional.
The Obama administration urged the Supreme Court to overturn the lower court decision, saying warrantless cellphone searches should be permitted because someone who has been arrested has a reduced expectation of privacy.
‘With all they contain and all they may reveal, they hold for many Americans the privacies of life.’
The California case stemmed from a 2009 incident in which police stopped a San Diego gang member, David Leon Riley, who was driving a car with an expired registration. Police inspected his cellphone and discovered information that linked him to a homicide.
The Fourth Amendment of the Constitution dictates that a warrant is typically required from a judge before police can conduct a search.
The justices acknowledged that their decision will affect the ability of law enforcement to combat crime, but they said warrants today can be obtained with greater speed and efficiency when justified.
Roberts took pains to draw a link between the intent of the Founders and the demands of modern technology.
The Fourth Amendment, Roberts wrote, was written in response to the reviled “general warrants” and “writs of assistance” of the Colonial era, when British officers conducted unrestrained home searches for evidence of criminal activity.
“Opposition to such searches was in fact one of the driving forces behind the Revolution itself,” Roberts wrote, citing a 1761 speech delivered in Boston denouncing such searches.
Cellphones today 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,” Roberts wrote.
To allow police to search all cellphone data as the contents of a suspect’s wallet or purse would be “like saying a ride on horseback is materially indistinguishable from a flight to the moon,” Roberts wrote.
Officers still will be permitted to conduct warrantless searches in exceptional circumstances, such as if a suspect is texting an accomplice who is believed to be about to detonate a bomb, or if a kidnapper might have information about a child’s whereabouts on his cellphone.
The court made its emphatic ruling at a time of major debates about the intrusion of American national security interests into the cellphone records and e-mails of everyday Americans. But whether such a stand for privacy will be applied in the national security interest is unclear.
While Segal of the ACLU said he believes the ruling will have far-reaching implications on how law enforcement conducts business, other legal experts say there is no way of guessing how it will be practically applied outside of cellphone searches.
“This is a very clear ruling about cellphone searches incident to an arrest. I would not extrapolate from it,” said Charles Fried, a Harvard law professor who served as solicitor general under President Reagan.
Fried pointed to a separate concurring opinion written by Justice Samuel A. Alito Jr., who invites Congress to weigh in and enact legislation that draws “reasonable distinctions based on categories of information.”
“Alito generally has been rather skeptical about honoring the concerns of the privacy Taliban,” Fried said.
Yet, Alito wrote, searching cellphones implicates “very sensitive privacy interests that this court is poorly positioned to understand and evaluate.”
Senator Edward J. Markey, a Massachusetts Democrat, said he plans to introduce legislation that would require law enforcement to obtain warrants for location-tracking requests they now routinely seek from cellphone carriers.
Related coverage:email@example.com. Follow her on Twitter @GlobeTracyJan.