Well, that's the idea behind "parallel construction" -- a clean evidence chain is built up in parallel. That one isn't exactly inadmissible and there is no proo

Well, that's the idea behind "parallel construction" -- a clean evidence chain is built up in parallel. That one isn't exactly inadmissible and there is no proof linking one chain to the other. Furthermore, there are protective policies where public prosecutors are given the discretion to exclude evidence gained from "confidential" sources (eg: undercover cops) and that revealing such evidence to the public would negatively impact current/future investigations. Such evidence can be revealed privately to the necessary parties (eg: judges), but I'm not familiar with these procedures.