Which case established the 'reasonableness' standard for searches and seizures, including the concept of probable cause?

Which case established the 'reasonableness' standard for searches and seizures, including the concept of probable cause?

• A. Wong Sun v. United States
• B. Katz v. United States
• C. Barnette
• D. Mapp v. Ohio

Answer: (B)

The question targets how the Fourth Amendment defines what counts as a search or seizure and when it requires justification. Katz v. United States reshaped this lens by focusing on a person’s reasonable expectation of privacy rather than on physical trespass alone. It held that government intrusion is a search when it violates that reasonable privacy expectation, even if no physical entry occurs. This privacy-based approach is what makes the standard of reasonableness central to Fourth Amendment analysis and, in practice, ties into the need for warrants grounded in probable cause in order to justify most searches or seizures. The other cases address different ideas—such as the exclusionary rule or specific contexts—not the fundamental redefinition Katz provided.

The question targets how the Fourth Amendment defines what counts as a search or seizure and when it requires justification. Katz v. United States reshaped this lens by focusing on a person’s reasonable expectation of privacy rather than on physical trespass alone. It held that government intrusion is a search when it violates that reasonable privacy expectation, even if no physical entry occurs. This privacy-based approach is what makes the standard of reasonableness central to Fourth Amendment analysis and, in practice, ties into the need for warrants grounded in probable cause in order to justify most searches or seizures. The other cases address different ideas—such as the exclusionary rule or specific contexts—not the fundamental redefinition Katz provided.