Covering Mapp v. Ohio, my Criminal Investigation class agonized today over the exclusionary rule. The exclusionary rule prohibits police from using evidence in trial if they gathered it in an unreasonable search. The Fourth Amendment clearly prohibits unreasonable searches, whatever those are, but it does not explicitly endorse the exclusionary rule.
The Supreme Court and my class clearly felt that they had to strain to fit the exclusionary rule into the Fourth Amendment. People hedged about necessity and justice, all, to my mind, unconvincingly.
I don’t think the exclusionary rule is complicated. To me it follows logically:
Premise (Fourth Amendment): The government can’t conduct unreasonable searches.
Premise (Due Process): The government has to convict you based on some investigation.
Conclusion: The government can’t convict you based on investigations that relied on an unreasonable search.
I don’t think there is any problem with the logical combination of the premises, and the second premise seems mostly reasonable. The exclusionary rule follows logically from the Constitution. The only problem is that the first premise is in fact false. The government can conduct unreasonable searches. It does them all the time – that’s why the court has to consider the exclusionary rule. When courts enforce the exclusionary rule they aren’t distorting the Constitution: they are enforcing its logical consequences. They are taking the Constitution seriously even though the police did not.