[rst]

"Fruit of the poisoned tree" is a peculiarly American doctrine which is recent as these things go; Wikipedia traces it to a court case from 1920.

And it's a somewhat problematic way of dealing with misconduct by the authorities. For one thing, it relies on them to correctly report where they're getting their information. Fast-forward to the recent NSA/DEA leaks, including memos offering agents explicit guidance in "parallel construction", a euphemism for constructing false case histories in which the existence of evidence from the NSA dragnet is concealed from the courts. Where this is happening, the exclusionary rule has failed as a constraint on the cops.