Summary
Highlights
The Fourth Amendment protects against unreasonable searches and seizures, requiring warrants based on probable cause. Initially, the Bill of Rights, including the Fourth Amendment, only applied to federal government actions, not state actions, as evidenced by cases like Fletcher versus Peck and Baron versus Baltimore. This changed with the 14th Amendment, particularly its Due Process Clause, allowing federal protection of citizens' rights against state governments through a process called selective incorporation.
Earl Warren, a former Republican governor of California, became a liberal Supreme Court Justice, reinterpreting the Constitution as a living document. The Warren Court utilized the 14th Amendment's Due Process Clause to selectively incorporate Bill of Rights protections, including elements of the Fourth Amendment, to apply to states. An example given is Miranda v. Arizona, which incorporated the Fifth Amendment's right against self-incrimination.
The Mapp v. Ohio case in 1957 involved police illegally searching Dollree Mapp's home without a valid warrant. Although they were looking for a bombing suspect and gambling machinery, they found obscene materials, leading to Mapp's arrest and conviction. The Supreme Court overturned her conviction, ruling that evidence obtained in violation of the Fourth Amendment (through illegal search and seizure) could not be used in state criminal proceedings. This established the 'exclusionary rule' and selectively incorporated the Fourth Amendment to the states.
Despite the exclusionary rule, there are significant exceptions. The 'plain view doctrine' allows evidence to be used if it's visible to law enforcement without a search. US versus Leon introduced the 'good faith exception,' where evidence obtained with a warrant believed to be valid by officers can be used even if the warrant is later found defective. The 'inevitable discovery doctrine,' from Nicks versus Williams, allows evidence if it would have been discovered through lawful means anyway. Additionally, the 'fruit of the poisonous tree doctrine' means any evidence derived from illegally obtained evidence is also inadmissible.