WASHINGTON — Chief Justice John Roberts didn’t hesitate last fall when a questioner asked him about the biggest constitutional challenge the Supreme Court faced.
Roberts told the audience at Rice University in Houston that the court must identify ‘‘the fundamental principle underlying what constitutional protection is and apply it to new issues and new technology. I think that is going to be the real challenge for the next 50 years.’’
The court has started the process, of course. In the recently completed term, a majority said technological advances in how quickly a warrant may be obtained means that in most cases police officers must obtain one before forcing a suspected drunk driver to take a blood test.
And, over a sharply worded dissent from Justice Antonin Scalia, the court went a long way toward endorsing DNA testing as the modern-day equivalent of fingerprinting. It approved of Maryland’s law that allows police to take DNA swabs at the time someone is arrested on charges of — not convicted of — a major violent crime. Now, amid a national debate over how much government should be able to find out about the private activities of its citizens in the name of combating terrorism, the next issue seems teed up for Supreme Court review: government searches of cellphone data.
About 85 percent of American adults carry one and they provide authorities with more than just a vast record of a person’s travels and phone calls. Modern smartphones have a memory capacity equal to that of a typical home computer in 2004, capable of storing millions of pages of documents.
‘‘That information is, by and large, of a highly personal nature: photographs, videos, written and audio messages (text, e-mail, and voicemail), contacts, calendar appointments, Web search and browsing history, purchases and financial and medical records,’’ Judge Norman Stahl of the US Court of Appeals for the First Circuit wrote recently. ‘‘It is the kind of information one would previously have stored in one’s home.’’
Stahl wrote for the majority in a 2-1 decision that applied the Fourth Amendment to the search of a cellphone found on a man arrested on charges of selling drugs. The amendment protects ‘‘the right of the people to be secure in their persons, houses, papers, and effects against unreasonable searches and seizures.’’
In most cases, a warrant is required. But the Supreme Court has said there are numerous exceptions to that general rule. In particular, in what courts refer to as ‘‘search incident to arrest,’’ a warrantless search is justified when officers are protecting themselves by looking for weapons or securing evidence that might be destroyed.
And justices have been lenient about allowing searches of items found on a person who has been legally arrested.
But Stahl and fellow Judge Kermit Lipez disagreed with the government’s contention that a cellphone is ‘‘indistinguishable from other kinds of personal possessions, like a cigarette package, wallet, pager or address book, that fall within the search incident to arrest exception’’ approved by the Supreme Court.
Stahl and Lipez endorsed a ‘‘bright-line’’ rule that warrantless cellphone data searches are ‘‘categorically unlawful’’ given the ‘‘government’s failure to demonstrate that they are ever necessary to promote officer safety or prevent the destruction of evidence.’’
Judge Jeffrey Howard, in a dissent, said his colleagues had no need to make such a broad ruling. ‘‘The constitutionality of a search cannot turn solely on whether the information is written in ink or displayed electronically,’’ he wrote.
The decision creates a split among courts that have examined the issue. The Florida Supreme Court, for instance, has ruled that police generally may not search an arrestee’s cellphone data, and some states have taken action legislatively.