What Supreme Court case determined that all states must follow the exclusionary rule regarding evidence that can be used in courts?

Mapp v. Ohio, 367 US 643 (1961)

In Mapp v. Ohio, (1961), the US Supreme Court held, "All evidence obtained by searches and seizures in violation of the Federal Constitution is inadmissible in a criminal trial in a state court." The exclusionary rule prevents evidence gathered through illegal or unreasonable search and seizure of a suspect from being used to prosecute the suspect in court.

This Fourth Amendment Search and Seizure protection, established in Weeks v. US, 232 US 383 (1914), originally applied only to federal cases because the Supreme Court hadn't incorporated much of the Bill of Rights to the States in 1914.

The decision in Mapp affected the entire law enforcement community, but the original ruling has been modified by subsequent decision to allow exceptions based on "good faith" and several other grounds.