In Mapp v. Ohio (1961), the Supreme Court developed which rule preventing police and prosecutors from using evidence gained through warrantless and unreasonable searches to convict people?

Exclusionary Rule, is the right answer.

Explanation:

In the history of the ruling of the Supreme Court of the United States the Mapp v. Ohio was a benchmark ruling. In this particular case, the Supreme Court declared that the exclusionary rule, that prevents the police and prosecutors from employing evidence obtained through unreasonable and warrant-less searches to convict the person, will be applied not only on the federal level but on the state level as well. The Supreme Court of the United States, in this case, employed the principle of selective incorporation to make the ruling.