Is the concern that the police will use these tools as a scaffolding and then use other evidence to build the case, then not mention the scaffolding? I’m not a lawyer but couldn’t a defense attorney just ask in cross examination about the evidence sources? If there is other independent evidence, that would have to stand on its own.
I'm not a lawyer either, but what you're referring to is called parallel construction, and it's not legal. Basically it comes down to 4th Amendment protection against unreasonable search. You can't use methods that violate the 4th Amendment to discover someone has done something wrong, then launch an investigation which uncovers evidence in the traditional sense. The whole process is poisoned because with the illegal means, they would have never had a reason to investigate. You can't just go fishing for criminals or else we are basically all considered guilty by default. The problem of course is that this does happen, and the prosecutors just lie, ommitting the source of the original evidence.
The problem is you also can't [easily] go fishing looking for parallel construction. Part of a parallel construction scheme is maintaining plausible deniability for the prosecution team and the trial witnesses.
Prosecutors sometimes lie. Normally they're just handed a case file with already laundered evidence, and it's not their responsibility to look behind the facially legitimate evidence.