The officials said one central concept connects a number of the court’s opinions. The judges have concluded that the mere collection of enormous volumes of “metadata” — facts like the time of phone calls and the numbers dialed, but not the content of conversations — does not violate the Fourth Amendment, as long as the government establishes a valid reason under national security regulations before taking the next step of actually examining the contents of an American’s communications.
This concept is rooted partly in the “special needs” provision the court has embraced. “The basic idea is that it’s O.K. to create this huge pond of data,” a third official said, “but you have to establish a reason to stick your pole in the water and start fishing.”
Under the new procedures passed by Congress in 2008 in the FISA Amendments Act, even the collection of metadata must be considered “relevant” to a terrorism investigation or other intelligence activities.
The court has indicated that while individual pieces of data may not appear “relevant” to a terrorism investigation, the total picture that the bits of data create may in fact be relevant, according to the officials with knowledge of the decisions.