Suppose police conduct an illegal search of a residence (no warrant, no consent, no probable cause) and find a dead body. There is plenty of evidence in plain sight that it was a murder and also evidence of who the killer is: he is standing next to the body with the murder weapon in his hand.
The murderer, being a smart lawyer, keeps his mouth shut.
Would all of the evidence found during the search be excluded under the "fruit of the poisonous tree" doctrine? If so, how could the murderer be prosecuted?