What does bulk surveillance look like in action? According to the case of Brandon Mayfield, it looks like a lot of loose ends and half-clues. An editorial in Al Jazeera America takes a look at the case, which saw a child custody lawyer from Portland, Oregon arrested on suspicion for the 2004 Madrid bombing, despite never having left the country.

The problems started with two latent fingerprints left on a bag of detonators involved with the bombing. When the FBI ran the prints through their database, they found 20 partial matches, one of whom was Mayfield, whose fingerprints were on record after an earlier stint in the military. As a converted muslim, he rose to the top of the list, at which point more coincidences started to pile up. He had represented an accused terrorist in a child custody case, and a FISA-warranted search of his computer turned up Google queries for tickets to Spain and pilot's lessons. It was all circumstantial, but the tactics of bulk collection provided a mountain of seemingly eerie coincidences to spur agents on. After months of intense surveillance, Mayfield ended up spending just two weeks in prison while the FBI pressed their case, but as the article points out, not every suspect will be as lucky. Read more details on Mayfield's case here.