Earlier quoted context omitted.
Is there any way to prove that is not NSA, say, and set up to only catch the biggest fish, or to always present parallel construction for criminals caught this way?
That's an interesting philosophical question.[1][2] [1] https://en.wikipedia.org/wiki/Burden_of_proof_(philosophy)#P... [2] https://en.wikipedia.org/wiki/Evidence_of_absence
Degree of proof is a relative: Maybe a terror organisation use PIA, NSA go fishing for evidence PIA has nothing. Terror org assassinate NSA head. PIA could be a front, but NSA head had to be willing to lose his life to hide the fakery, and terror org wasn't a big enough fish ... more likely you're currently in a coma. Lots of places for false premises to creep in.
Dial it back, is there a point where there'd ever be enough evidence?