Final answer:
Mapp v. Ohio established the exclusionary rule, making evidence obtained illegally in violation of the Fourth Amendment inadmissible in state courts and influencing how such evidence is treated in court proceedings.
Step-by-step explanation:
The Mapp v. Ohio case had a significant impact on court proceedings. This landmark decision established that evidence obtained through illegal searches and seizures, in violation of the Fourth Amendment, is inadmissible in state courts. This enactment of the exclusionary rule at the state level meant that any evidence seized without proper legal authority could not be used to convict someone at trial. Moreover, the principle extends to the 'fruit of the poisonous tree,' which includes any evidence discovered as a result of the initial illegal search or seizure.