Illegally obtained evidence – It is the evidence obtained illegally or in violation of a law or of constitutional requirement.
Fruit of the poisonous tree doctrine – is a doctrine that the evidence obtained illegally is not admissible in the court of law.
Example: State agents A and B went to search C’s house who was suspected of raping D, in the absence of a warrant. A and B found D’s underwear inside C’s house, arrested C, and was prosecuted.
Illegally obtained evidence is obtaining of the underwear, and the act of prosecution will fail because it is an act resulted from the illegal act of obtaining the evidence, thus the act of prosecution is the fruit of the poisonous tree.