Fruit of the poisonous tree

Fruit of the poison tree is a legal principle that says evidence found or gathered in a way that breaks a law cannot be used in court. So, if the police find something that is helpful for their case because they did something wrong (like going into your house without a proper search warrant), then the judge won't let them tell the jury about it. That evidence is like a poison tree - it was found in a bad way, so the ‘fruit’ (or evidence) it produces cannot be used.