The FBI has the power to collect massive amounts of data and communications during its investigations. This power periodically ingests NATSEC steroids, pumping the FBI's data stores full of stuff not relevant to the NSA's work, but possibly relevant to the FBI's crime-fighting duties.
You would think the FBI would toss anything not relevant to an investigation. Just in terms of storage and haystack-sorting, it would only make sense to discard data/communications not needed for ongoing investigations. But you'd be wrong. The FBI holds on to everything it gets because you never know: the irrelevancies you hoovered up yesterday might be useful today.
That's pretty much what happened to Aaron Swartz, according to documents published by Dell Cameron of Gizmodo.
Nearly two years before the U.S. government’s first known inquiry into the activities of Reddit co-founder and famed digital activist Aaron Swartz, the FBI swept up his email data in a counterterrorism investigation that also ensnared students at an American university, according to a once-secret document first published by Gizmodo.
The email data belonging to Swartz, who was likely not the target of the counterterrorism investigation, was cataloged by the FBI and accessed more than a year later as it weighed potential charges against him for something wholly unrelated.
The data collected -- most likely obtained with an NSL -- came from Pittsburgh University. It was part of a data haul associated with the FBI's terrorism investigation. Swartz was never the target of this Al-Qaeda investigation but the information obtained remained in the FBI's data stores even though the FBI had no reason to hold onto non-hit data.
When the FBI did start looking in Swartz's activities, it found his email address in the stored data it had obtained from the university in 2007. This apparently happened in 2008, around the time the FBI was trying to determine if Swartz had violated any laws by freeing millions of court documents from PACER.
The FBI targeted a foreign terrorist entity but ended up with an untold amount of email metadata originating from US persons' accounts. The only reason we're seeing any evidence of the FBI's backdoor domestic searches come to light is Aaron Swartz's inadvertent involvement. If it hadn't been for a high-profile prosecution and Swartz's tragic suicide, public interest in the FBI's investigative activities surrounding Swartz would likely have minimal public interest. But Swartz's prosecution and death have put more eyes on the case, including those of transparency group Property of the People, which obtained this document through an FOIA lawsuit against the agency.
This document is more evidence the FBI abuses its investigative privileges. The agency engages in foreign-facing terrorism investigations, hoovering up as much "relevant" data as it can. Rather than discard everything not related to the investigation, the FBI stores it indefinitely. When the FBI opens a domestic investigation, it can give itself a head start by digging through its data stores for info it has "inadvertently" gathered on American citizens. The information the FBI already has on hand -- info it really can't justify keeping -- helps build cases against Americans while depriving them of their right to challenge the evidence against them. Americans don't know about this evidence because it's laundered by NSLs, warrants, and whatever else the FBI needs to deploy to duplicate the results of data store searches the agency has already performed.