Final answer:
In the case of Mapp v. Ohio, the Supreme Court ruled that the constitutional protection against unreasonable search and seizure applies to state governments as well, prohibiting the use of illegally obtained evidence in state courts and establishing the exclusionary rule.
Step-by-step explanation:
In Mapp v. Ohio, the Supreme Court extended the constitutional protection against unreasonable search and seizure to action by state government. This landmark decision in 1961 held that evidence obtained in violation of the Fourth Amendment, which protects against unreasonable searches and seizures, is inadmissible in state courts.
This established the exclusionary rule, which requires that illegally obtained evidence must be excluded from trial. Hence, the ruling placed an imperative on all levels of government to abide by the Fourth Amendment.
The case was significant as it incorporated the Fourth Amendment protections to the states through the Due Process Clause of the Fourteenth Amendment.
This meant that individual freedoms were safeguarded not only from federal violations but also from those by state authorities. This decision also introduced the "fruit of the poisonous tree" doctrine, which prohibits evidence derived from illegal searches and seizures from being introduced in court.