Ever read Neal Stephenson's Cryptonomicon? The WW2 part shows a team going through elaborate measures to create a plausible way that the allies can find out what the Germans are up to without revealing that they can read all of their messages. They would tell a submarine to surface at a particular location at a particular time and report what they see, for instance, and the sub crew would have no idea why, to produce a plausible explanation of why some German action was discovered.
Parallel construction often means they hide how they got the original information from the court and from the defense.
The neat thing is those parts of Cryptonomicon were largely based on things that actually happened:
No, that’s not how it works at all. You use illegally gained information to find other avenues to get evidence that on the surface look ok.
For example, you use illegally gained access to messages to find out about a meeting at a particular time. Then when the meeting to exchange contraband is happening, “a concerned anonymous citizen” calls in a tip of suspicious behavior and a patrol cop stumbled onto a bust.
The evidence is not admissible. It is considered 'fruit of the poisoned tree'.
Parallel construction only works if you can hide the illegal investigation from the court.
Even if the method used was illegal, and found to be illegal in court, the evidence is still admissible iirc?