“Every day, law enforcement officers are using this data to place suspects at the scene of murders and other crimes,” said Weinstein, now a partner at Steptoe & Johnson.
Data about a communication may be just as revealing as the content itself, said Christopher Soghoian, principal technologist with the American Civil Liberties Union.
“If you call an abortion clinic and make an appointment, the fact that you’re making the appointment is far more sensitive than what time your appointment is,” he said. “If you’re calling Alcoholics Anonymous or a suicide counselor, what you’re saying will certainly be sensitive. But the fact that you’re calling Al Anon or a suicide counselor is extremely sensitive, too.”
Under U.S. law, it’s easier for the government to obtain metadata than content. Authorities generally need to show probable cause for a wiretap or intercept of communications.
Telephone records, but not e-mail metadata, can be obtained by law enforcement agencies without any kind of court order.
Weitzner said metadata is “arguably more revealing because it’s actually much easier to analyze the patterns in a large universe of metadata and correlate them with real-world events than it is to go through a semantic analysis of all of someone’s e-mail and all of someone’s telephone calls, if you could get that.
“Metadata is objective: I called you. You called me.”
Cellphone data helped Italian authorities identify CIA agents who abducted an Egyptian cleric suspected of terrorist involvement in Milan in 2003. The investigators pulled the records and identified the agents by their aliases, where they had stayed and whom they had called — including each other. Similarly, in 2011, Hezbollah identified a half-dozen CIA informants through analysis of their cellphone records and calling patterns.
Critical as metadata is, Weinstein said, it does not give you the subject’s words and thoughts. “Only the content,” he said, “will provide you with the evidence you need that the conversations are about terrorism or other crimes.”