I had a judge once tell me that the police absolutely have the right to commit crimes to gather evidence in an investigation.

(mostly true -- for instance an officer can generally commit innumerable felonies as long as nothing they do violates your personal constitutional rights -- rarely is evidence thrown out because it was obtained in violation of a statute unless that statute includes a provision for exclusion, e.g. wiretapping laws)

The individual who would prosecute them also needs to work with them to prosecute civilians. So pretty much, so long as it isn't murder.

Exactly this.

Maybe this particular judge didn't for whatever reasoning, but judges definitely prevent a prosecutor from introducing evidence based on how it was collected. This is why concepts like "fruit of poisonous tree" and "parallel construction" exist.

Doesn't parallel construcction mean that judges actually don't care how evidence was collected? They can't possibly care that much if they are fine with a fig leaf like parallel construction.

No.

Parallel construction means they have an illegal bugging device in the courthouse bathroom, and use a conversation that you have with your attorney to identify a witness. Then they independently arrest the witness for something and pressure them to testify.

Basically... yeah.

It's using illegally obtained evidence (like an NSA wiretap) to point the detectives in the right direction they would have otherwise never probabilistic-ly searched.

Parallel construction means the judge doesn't know.

Or can at least plausibly pretend not to.

I guess that is true, although you'd be hard pressed to prove that. I don't think any court would hear a complaint about a lower court or adjacent court having participated willingly in parallel construction.