Mapp v. Ohio established which constitutional principle?

• A. Exclusionary Rule
• B. Miranda Rights
• C. Double Jeopardy Rule
• D. Probable Cause standard

Answer: (A)

The principle tested is that evidence obtained in violation of the Fourth Amendment cannot be used in court, and this rule applies to both federal and state prosecutions. Mapp v. Ohio extended the Exclusionary Rule to the states by holding that the Fourth Amendment’s protections against unreasonable searches and seizures are incorporated against state governments through the Due Process Clause of the Fourteenth Amendment. This means that illegally obtained evidence is inadmissible in state trials just as it is in federal trials, serving to deter unlawful police conduct and to safeguard individual privacy.

Before this decision, the exclusionary rule had been limited to federal cases (Weeks v. United States) and some states argued that it did not have to apply to state courts (Wolf v. Colorado). Mapp overruled that position and ensured uniform protection across all courts.

Notes on the other options: Miranda Rights concern interrogation and the right to counsel and silence, not the admissibility of evidence. The Double Jeopardy Rule protects against being tried twice for the same offense. The Probable Cause standard governs when searches or arrests are permissible, but the rule in question specifically addresses the admissibility of evidence, not the threshold for searches or interrogation.