The policy set forth in Mapp v. Ohio is the exclusionary rule. Specifically, this case applies the exclusionary rule to the states. What this means is that state courts cannot admit evidence that has been acquired through an illegal search or seizure. This policy requires a court to balance the individual right to be free from illegal searches and seizures with the government’s interest in keeping law and order in the society. This is a fundamental balancing act that goes on at all times (notably, it is in the news today with the federal government’s collection of Americans’ phone records) in a democracy.
Governments have an interest in maintaining law and order. This is helped if the government can seize evidence of crimes and use it to prosecute suspects. The more the government has the ability to seize evidence, the more likely it is that criminals will be caught and law and order will prevail.
However, this must be balanced against our right to be free from a police state. We do not want to live in a society where the police may search us at any time regardless of whether they have a reason to do so. Therefore, we also have an individual interest in being free from unreasonable searches and seizures. This interest must be balanced against the government’s interest in maintaining law and order.