The fruit of the poisonous tree is an important legal idea that essentially states that anything related to an illegal means of gathering evidence is also illegal, even if it did not come directly from the primary event. When the law was broken the first time, it meant that all discoveries made by the authorities—that were only possible because of the illegal action—could not be used as evidence. This is one way that you can sometimes get evidence thrown out of court.
For example, the police typically need a warrant to come into your home and search it. If they neglect to get a warrant, come into the home anyway, and find illegal drugs, records of drug sales, or anything else related to drug crimes, they can’t use that evidence in a court case.
This is done to ensure that the authorities take the proper steps. They actively don’t want to find evidence illegally, especially if they’re worried that it’s the only hard evidence they may find, because they could then lose an easily winnable case due to the fruit of the poisonous tree doctrine.
Other examples of illegally obtained evidence include that found after illegal traffic stops, illegal interrogations, and the like. For instance, during an illegal interrogation, a suspect may admit to the location of key physical evidence. The authorities may then go pick it up. Even though it was not found at the time that the law was being broken, that physical evidence has to be thrown out because they found it due to the unlawful interrogation.
Those who are facing drug charges in Illinois need to know how this works when they think evidence was seized and searches were carried out in an unlawful manner, as they may be able to have that evidence removed from the case.
Source: Cornell Law School, “Fruit of the Poisonous Tree,” accessed Feb. 22, 2016