As investigators hunt for clues in Monday’s Boston Marathon bombings, they’re zeroing in on a surveillance video from a local store showing a man placing a black bag at the second bombing site. But could one other detail from the footage end up being the crucial lead?
In the video, the suspect, wearing a backwards baseball cap and hoodie, is on a cellphone. That fact could open the door to wealth of useful information, experts told msnbc—likely giving them a detailed picture of the movements and contacts of the man they’re looking for, and perhaps even his name.
“This is going to give us a tremendous amount of evidence,” said Ben Levitan, a telecom specialist who has served as an expert witness in numerous telecom wiretap cases.
Levitan explained how investigators would proceed: Every cellphone call is connected to a specific cell tower. Since they know the man’s location when he was on the call, they can easily find which cellphone tower—and even which side of that tower—the call went through.
Of course, in a crowded area like Boston’s Copley Square during the marathon, there might be as many as one hundred other calls using that same side of the tower at the same moment. But Levitan said it would be “easy forensics” for law enforcement, using data provided by telecom companies, to do what he called a “cell tower dump,” then use some basic investigative legwork to sort through all one hundred of those calls to find the one they’re looking for.
In the best case scenario, said Bruce Schneier, a prominent digital security expert, that would give investigators the name of the phone’s owner. Even if there was no name associated with the phone—for instance, if it had been paid for with cash—it would still tell them who the person talked to, and where he had been with the phone, likely going back to around last October.
“You can create an entire map of the person’s activity from his cellphone records,” said Mike Baker, a former covert CIA operative who knows runs a private intelligence firm. “There’s a tremendous amount of information that’s going to be gathered.”
The CIA used similar methods to find Osama bin Laden, Levitan pointed out. “Once they got the courier’s number, every time he moved, they were able to track his location,” he said.
Of course, the bomber could have been smart enough to acquire the phone right before planting the bomb, and to have thrown it away right afterwards. But both Baker and Schneier said real-life criminals are often far less savvy than their counterparts on C.S.I.
“It’s just one more piece of the investigation that’s gonna be very helpful,” Levitan concluded.
Are there civil liberties concerns triggered by the wealth of information available to investigators? Absolutely not, said Schneier, because the FBI will get a warrant from a judge. That makes the situation very different from those cases in which the government has conducted warrantless wiretapping, which have raised legitimate civil liberties issues, he explained.
“This is exactly what we want to happen,” Schneier said. “The police get the warrant, and they catch the bomber.”