This has been my concern since I first heard about the NSA's bulk data collection. They seem to only be searching for evidence that would prove guilt and not collecting evidence that would prove innocence. The presumption of innocence is also gone. Of course, without any evidence of false prosecution, its only a concern, except:
This is awful. Its absurd that the primary evidence that led the FBI to suspect Mayfield, the fingerprints, were not actually his. Instead, they ignored that evidence and proceeded to build a case against him because of some circumstantial evidence. This should not happen under any condition.