Which case created the exclusionary rule preventing illegally obtained evidence from being used in court?

• A. Mapp v. Ohio
• B. Miranda v. Arizona
• C. Gideon v. Wainwright
• D. Plessy v. Ferguson

Answer: (A)

The key idea is the exclusionary rule, which says evidence obtained through illegal searches or seizures cannot be used in court. The case that established this rule for state courts is Mapp v. Ohio. In that decision, the Supreme Court held that the Fourth Amendment’s protections against unreasonable searches and seizures apply to the states through the Fourteenth Amendment, so illegally obtained evidence must be excluded from state criminal prosecutions. This extended the federal exclusionary rule (originating with Weeks v. United States) to state courts and solidified the protection against unlawful police conduct.

Miranda v. Arizona, while famous for warning suspects of their rights during custodial interrogation, deals with self-incrimination and counsel, not the admissibility of evidence solely due to an illegal search. Gideon v. Wainwright ensures the right to counsel, not the exclusion of illegally obtained evidence. Plessy v. Ferguson addresses racial segregation and has no bearing on how evidence is admitted or excluded in court.

So the best answer is Mapp v. Ohio because it directly established that illegally obtained evidence cannot be used in court, applying the Fourth Amendment to state prosecutions.