The NSA take a leak from a height on fourth amendment protections and "produce" falsified evidence trails. They do so at times when they have no right to. They have no mandate for domestic crime and yet as the quote and documents below reveal, they snoop for it and set up arrests. After that, the instruction is to cover up the evidence trail. This is what has come to light, I doubt it would have without Snowden. [0]
[0] https://en.wikipedia.org/wiki/Parallel_construction
http://www.reuters.com/article/2013/08/05/us-dea-sod-idUSBRE...
"If the intelligence community collects information pursuant to a valid foreign intelligence tasking that is recognised as being evidence of a crime, [it] can disseminate that information to law enforcement, as appropriate." [1]
[1] http://www.theguardian.com/world/2013/aug/06/justice-departm...
EDIT: where I have written "produce" above I had initially written set up, the course of action is as follows.
NSA tip off SOA/DICE re: domestic crime, SOA/DICE instruct DEA/IRS to have police stop suspect at location for e.g. "traffic violation" and create a parallel evidence chain - so that source of information cannot be determined.