The scene on Boylston Street last week was horrific: two homemade explosive devices, reportedly packed with nails and ball bearings, blasting through crowds of innocent men, women, and children out to enjoy a marathon on a sunny spring afternoon. Images of a blood-soaked sidewalk beamed across the world, provoking a familiar mix of fear and confusion—a gut-wrenching feeling that residents of New York, London, and Madrid know all too well. The political response, still developing, has also been familiar: Proponents of more surveillance have been making their case aggressively, some, like Rep. Peter King, R-N.Y., demanding more monitoring of Muslim communities in order to prevent a similar atrocity from occurring. Others are also calling for increased surveillance—like my Slate colleague Farhad Manjoo.
But it was not a lack of existing surveillance capabilities that allowed the Boston perpetrators to slip through the net. A vast surveillance infrastructure was already available to the authorities—and was exploited to investigate suspects Tamerlan and Dzhokhar Tsarnaev both before and after the bombings. The FBI has confirmed that in 2011, it probed Tamerlan’s activities at the request of Russia over concerns that he was a follower of radical Islam who was planning to join unspecified “underground groups.”
The bureau says that two years ago, it checked Tamerlan against government databases to look for “derogatory telephone communications”—presumably those perceived to be disparaging to the United States—and his potential use of websites associated with “the promotion of radical activity.” It also scrutinized his links with other persons of interest, trawled through his travel and education history, and interviewed his family. The FBI says that at the time, it did not find any terrorism activity, domestic or foreign.
A source at the bureau, who provided information on the condition of anonymity, told me the feds did not spy on the content of Tamerlan’s communications because they could not find a terrorism connection and so did not have the evidence necessary to obtain a warrant. (A government official told the New York Times that the FBI had sought additional information from Russia in order to justify a search of phone records and “other more restricted information,” but received no reply.) In other words, this means that instead of eavesdropping on Tamerlan’s calls or looking at his emails, the feds searched for existing intelligence about him already stored on government computers. What the bureau meant by looking into “derogatory telephone communications,” the source said, was that they checked a database for any previously lawfully obtained records.
With the benefit of hindsight, it’s easy to argue that the FBI should have kept a closer eye on Tamerlan in light of Russia’s initial request. But even so, the Tsarnaev brothers’ alleged plot slipping under the radar cannot be blamed on a lack of surveillance capabilities—if anything, it should be attributed to human error. No system can be foolproof, and it’s no different in the age of Big Data. Every day, in all likelihood, individuals like Tamerlan cross the desks of U.S. authorities. As of 2007 the government had amassed a list of more than 700,000 names of suspected and known terrorists—with records being added at an astonishing rate of 20,000 every month on average. Surveillance powers allow the National Security Agency to intercept communications passing between the United States and foreign countries and pick out key words and phrases automatically. But due to the sheer volume of communications, it is inevitable that some threats will go undetected. In the United Kingdom, for instance, the chief of domestic security agency MI5 was quoted in a government report last year admitting that it was gathering so much “digital intelligence” that at one point “over half was not being processed.”
Where surveillance has indisputably proved itself useful is in retrospective investigation. In Boston, it was an extraordinary feat that within a matter of days, in a city of some 630,000 people, the authorities were able to home in on the two individuals they believe were responsible for the attacks—largely thanks to security camera footage, some of which is still not released and is said to be “highly incriminating.” The cops were also reportedly able to use cellphone tracking to find the brothers on Friday, after they stole a car and shot an MIT policeman in a frenzied series of events that ultimately led to their capture.
But the idea that more ubiquitous surveillance—whether in the form of cameras or eavesdropping—would have prevented the attacks is impossible to prove. Those arguing for increased surveillance as a pre-crime tool “to spot criminal activity before it happens,” as Manjoo has written, misunderstand the level of surveillance that is already being conducted—and the difficulty of finding a needle in haystack. Even if we were to take the argument for more surveillance to its logical extreme and cram the skies with spy drones and install Trojan keyloggers on the computers of every citizen in the United States, an intelligent lone-wolf attacker bent on causing destruction will still find a way to evade detection in order to wreak havoc.
You can plant a camera on every street corner, fitted with software supposed to detect suspicious behavior. However, no amount of security will address the underlying issue—the terrorism, which is existential and usually rooted in some sort of political grievance that simmers like a volcano only to intermittently erupt. Surveillance can be a useful law enforcement tool, no doubt. But it is not a panacea.
