Final answer:
In the landmark Supreme Court case Mapp v. Ohio, it was decided that evidence obtained in violation of the Fourth Amendment is inadmissible in state courts, solidifying the exclusionary rule at all government levels. The correct answer is option A. Yes.
Step-by-step explanation:
The Supreme Court case of Mapp v. Ohio set a significant precedent in criminal law, determining that evidence obtained illegally, in violation of the Fourth Amendment, cannot be used in state criminal proceedings. This decision extended the exclusionary rule, which was initially established federally in Weeks v. United States, to the state courts. The ruling established the principle known as the "fruit of the poisonous tree", meaning that not only is evidence obtained directly from an illegal search or seizure inadmissible, but also any evidence later developed as a result of the illegal act.