海角大神

In a 5-to-4 decision today, the US Supreme Court updated privacy protections in the digital age, ruling that historic location data collected by from individual cellphones is protected by the Fourth Amendment of the Constitution.

Given the routine advancement in communications technologies, especially in recent years with the proliferation of smartphones, the Fourth Amendment protection against unreasonable searches by the government has been one of the most routinely reinterpreted constitutional amendments. The decision this morning 鈥� in which Chief Justice John Roberts sided with the court鈥檚 four left-leaning justices 鈥� continues that trend, and reinforces suspicions the high court has voiced in the past about how rapid technological advancements could implicate personal privacy.

Chief Justice Roberts was careful to detail the narrow parameters of the majority鈥檚 decision in his 27-page opinion. Nevertheless, four separate dissenting opinions totaling 92 pages suggests that lower courts now have a significant task ahead of them tackling the many questions the decision is likely to raise.

鈥淚t鈥檚 a gigantic decision for Fourth Amendment jurisprudence,鈥� says Christopher Slobogin, director of the Criminal Justice Program at Vanderbilt Law School. 鈥淚t is in large part a result of the court鈥檚 realization that technology is changing the relationship between the government and its citizens.鈥�

鈥淚f read broadly, [the decision] could have a huge impact on law enforcement,鈥� he adds, but 鈥渢he majority is careful to limit its decision, and lower courts can draw distinctions between this case and other cases.鈥�

'Seismic shifts' in technology

The case concerns the arrest and conviction of Timothy Carpenter, who led a string of cellphone store robberies in Michigan and Ohio in 2010. Law enforcement was able to place him near the scenes of the robberies when they occurred in part by collecting 127 days of Mr. Carpenter鈥檚 cell-site location information from cell towers operated by MetroPCS and Sprint 鈥� information they were able to obtain under a law requiring them to show only that the data was 鈥渞elevant and material鈥� to the ongoing investigation.聽

Carpenter argued that such a vast swathe of data was protected by the Fourth Amendment 鈥� thus requiring law enforcement to show probable cause that he was involved in a crime before being able to seize it. Lower courts had ruled against him in part because the data had been seized from a third party, and because he had 鈥渧oluntarily鈥� given it to them by using his cellphone. Today, five Supreme Court justices instead agreed with Carpenter.

The specific facts of the case are important because the majority opinion refuses to look beyond them.聽

鈥淥ur decision today is a narrow one,鈥� Chief Justice Roberts wrote in . Essentially: the decision expands Fourth Amendment protections to a week or more of cell-site location information and no further. The questions of whether such information collected for a shorter period, or in real time, for example, were left for another day.

Roberts nevertheless voiced serious concerns about 鈥渢he seismic shifts in digital technology鈥� presented in the case, and about both the current and future potential for abuse if the government is able to collect a week or more of a person鈥檚 location data without having to show probable cause.

Comparing a modern cellphone to an ankle monitor in how precisely they each track the users鈥� movements, he wrote that the government is able to 鈥渢ravel back in time to retrace a person鈥檚 whereabouts,鈥� adding that with 400 million devices in the country constantly pinging their location to cell towers 鈥渢his newfound tracking capacity runs against everyone,鈥� not just those under investigation.

鈥淭his case is not about 鈥榰sing a phone鈥� or a person鈥檚 movement at a particular time,鈥� he added. 鈥淚t is about a detailed chronicle of a person鈥檚 physical presence compiled every day, every moment, over several years.鈥�

Significantly, the decision factored in how the technology has advanced since Carpenter鈥檚 arrest in 2010. Back then, investigators were only able to place in a sector ranging from one-eighth to four square miles. Today, wireless carriers can pinpoint a phone鈥檚 location within roughly 50 yards.

That could pave a way for the Fourth Amendment to be expanded to protect other kinds of data, says Jennifer Lynch, a senior staff attorney for the Electronic Frontier Foundation, which supported Carpenter in the case.

鈥淭here is a lot of this case that could apply to third-party tracking of other parts of our lives,鈥� she says. 鈥淚t recognizes that we can have a reasonable expectation of privacy in records we share with third parties鈥� 鈥� records such as emails and smart meters in homes.聽

Impact on law enforcement

The four dissenting justices voiced several complaints and concerns. Justice Anthony Kennedy, joined by Justices Clarence Thomas and Samuel Alito, wrote that the court should have maintained 鈥渞elevant Fourth Amendment precedents and principles,鈥� such as constitutional protections not extending to personal information held by third parties or given up voluntarily by an individual.

Furthermore, Justice Kennedy added, the decision 鈥渨ill undermine traditional and important law enforcement practices; and will allow the cell phone to become a protected medium that dangerous persons will use to commit serious crimes.鈥�

Lawrence Rosenthal, a聽professor at Dale E. Fowler School of Law at Chapman University in Orange, Calif., agrees. The fact the high court has written a decision based in part on how technology could evolve in the future means 鈥渢he specter of whether the government鈥檚 going to go after all our information鈥� has taken precedence over 鈥渟ophisticated [police] work.鈥�

鈥淲hat we wind up with is a choice between a conceptual or a pragmatic Fourth Amendment. And I鈥檇 say the conceptual fourth amendment is winning,鈥� he adds.

Unanswered questions

The Fourth Amendment has always been interpreted somewhat conceptually, however. Originally it only considered 鈥渉ouses, papers and effects鈥� subject to these kinds of privacy protections. In the 19th century, after the postal service was established, it was expanded to include the contents of mail, and in the 1970s it was expanded again to include the contents of telephone conversations.聽

For the short-term, the Supreme Court has kept its decision narrow to try and avoid significant disruption. Requiring law enforcement to get a probable cause warrant only if they want to collect a week or more of location data is one example of that. Police could 鈥� and currently do, according to what Professor Slobogin says cops have told him 鈥� collect just a few days-worth of location data and use that to prove probable cause and get a warrant for longer surveillance.聽

Other unanswered questions will have to be hashed out over time in the lower courts, however.聽

As Kennedy queried in his dissent, limiting the decision to just long-term cell-site location data means the court has also 鈥渉eld that individuals do not have a reasonable expectation of privacy in financial records鈥� or records of who a person calls聽鈥� information that 鈥渄warfs what can be gathered from cell site records.鈥澛�

For now, however, the high court has taken a notable step by acknowledging the new challenges technological advancements are posing for individual privacy.

鈥淵ou didn鈥檛 used to be able to carry your entire life in your pocket, and now you can,鈥� says Slobogin.

鈥淩oberts is realizing technology is changing the name of the game,鈥� he adds, 鈥渁nd it鈥檚 high time the court made this recognition.鈥�

Staff writers Peter Grier and Harry Bruinius contributed reporting to this story.聽

Correction: Chapman University is located in Orange, Calif.