The jurisprudencial theory of "the fruits of the poisoned tree"
The theory of "the fruits of the poisoned tree" is a doctrine that refers to the evidence of a crime obtained illegally, which will prevent later in the judicial process that it can be used against any person, in the sense that any evidence that directly or indirectly and for any reason is flawed, must be invalid evidence.
An example could be obtaining a piece of evidence without respecting the legality control, causing it to become illegitimate, and therefore, this would mean its radical nullity, meaning that all other proof directly related and derived from the procedure followed are also null and void.
Likewise, we could cite other examples, like those cases based on obtaining evidence with violation of the right to privacy, the secrecy of communications or the inviolability of the home, the latter regulated in article 18 of our Constitution.
This theory is a legal figure originated in the Silverthorne Lumber Company case against the United States; following a search, government agents entered W. Silverthorne's offices and he was arrested for the ledgers found in the search. Subsequently, he appealed in court, invoking the fourth amendment to his Constitution, declaring all the evidence obtained illegal.
The simile here is that to make use of an illegal evidence (tree) that leads to an illicit discovery (fruit). The evidence would be declared null for not respecting a legality control –violation of constitutional rights–. The doctrine of the "fruit of the poisoned tree" is exemplified in the entry into the home of an aggressor without judicial authorization, and videos are obtained in which situations of aggression are recorded. The tree (entering the home violating its right to inviolability) and the fruit (videos obtained violating the right to privacy). The probative result is illegitimate and its nullity cannot be remedied, and will drag all other related and derived evidence.
As a conclusion, as Matthew said in the Bible, any tree that bears poisoned fruit should be cut from the roots, thus avoiding the source that has poisoned the tree so that it bears bad fruit.