http://www.dailydot.com/politics/nsa-dea-fbi-snowden-doj-oig/Long story short, NSA legally or illegally wiretapped US citizens. They then would give the data to the FBI, DEA and other federal agencies. Those agents would lie under oath, also known as committing perjury, about the source of information in court. This is known as parallel construction.
Example?
NSA intercepts Fistful's phone calls, text messages, internet traffic and other useful metadata. All very harmful stuff that laypersons don't understand is bloody important and generally not legally separate from the actual content, but people pretend it is. Fistful's cell for example leaves very detailed, but not extremely granular, locational data. NSA charts Fistful's position over a couple weeks, and then emails it to the DEA. The the DEA stakes out the highway Fistful is likely taking. He's pulled over for speeding, suspected DUI, whatever. An on-hand drug dog finds a bottle of aspirin (or weed or Brady Center propaganda) in his glove box, that he is arrested. Under oath, officers swear it was a random search and not illegally collected data from the NSA. This is to bypass giving information on our domestic surveillance capacity, as well as bypass "fruit of the poisonous tree" legal protections, by lying to prosecutors and judges.
Generally, evidence collected from illegal searches is excluded. Unless you commit perjury, of course. Having been caught, they've been taken to using third parties as proxies. For example, DEA wouldn't tell its agents or other departments were the data came from. DEA's Special Operations Division simply say "Randomly pull over a 1971 line green AMC Gremlin on Route 123."
So, in other words, violations of the Fourth Amendment and perjury committed in court rooms is bigger and more institutionalized than previously thought. Shocking, I know.
