Ah, but you forget that he represents a case of "The Fruit of the Poisonous Tree"!
You know, the principle that if you find 20 murdered bodies in someone's cellar and video of a guy doing the killing after an illegal search, it means that the guy is innocent.
The
"Fruit of the Poisonous Tree" principle is one of the most publicly misunderstood doctrines in Law, right alongside
"hearsay" and the BS claim that
"a failed attempt to commit a crime means no crime was committed" that Trumpistas keep trotting out.
Firstly, this evidential exclusion doesn't even apply in the case of impeachment, it only applies in Law and only when the accused has had his 4A rights violated. This happens when an Officer of the Law or an agent of the government (that bit is very important) has illegally searched an area which is covered by the accused's 4A rights, i.e. in an areas in which he/she has the right to privacy - usually the person's home or property or vehicle, or under very limited circumstances, his/her place of work. The search must be illegal through either no warrant or an illegally obtained search warrant.
Examples of exceptions to the exclusion rule;
1. Discovery of evidence as a result of an independent source
Your neighbour knows you have committed a crime. One day, your neighbour is visiting you. He takes a piece of incriminating evidence and passes it to Police. Your 4A rights have not been violated because there was no illegal search by the Police (although your lawyer could argue
"chain of custody issues")
2. Inevitable discovery
You keep incriminating evidence in your top drawer at your place of employment, you have no 4A rights. If the business owner grants the Police permission to search your desk, any evidence so obtained will be admissible. Even if the owner wasn't there to give permission, the Police would have discovered the evidence anyway with a warrant issued to the owner
3. The Good Faith exception
Police obtain a search warrant based on information they believe to be true. They find incriminating evidence. Later it turns out the the information was wrong and the search warrant was not valid on probable cause, however, it was obtained and executed by government agents in good faith. The evidence is admissible.
Even if the exclusion rule did apply to impeachment, two exceptions would apply
1. The Independent Source Exception - the whistleblower is not an agent of the government
2. The Good Faith Exception - the whistleblower believed he was right to do what he did (and he was, because his actions were protected by US Federal Statute).
