Today is the final post on warrants—at least for now.

I’ll start with a story. In 1957, Cleveland police were looking for evidence of a bombing, and although Dollree Mapp wasn’t the suspect, they believed she might have evidence in her home. But she refused to let them in. So they returned a few hours later, waving a paper and claiming it was a search warrant. She snatched the paper and shoved it down the front of her dress; they wrestled her and took the paper back. With Mapp in cuffs, they proceeded to search her house. Inside a trunk in the basement they found pornographic books and pictures (the property, Mapp said, of a previous tenant). They arrested Mapp and prosecuted her for possession of illegal pornography. No warrant was ever produced at trial. It’s pretty clear none ever existed.

Mapp appealed her conviction all the way to the Supreme Court, arguing that because police did not have a warrant, the search violated her 4th Amendment rights. Therefore, she said, the evidence should be thrown out of court and her conviction overturned.

In Mapp v. Ohio, SCOTUS agreed. They articulated the exclusionary rule, which says that illegally obtained evidence can’t be used in court. This is a powerful rule because it means that sometimes people we know are guilty will still go free because the cops screwed up. But, the Court said, the rule was the only realistic way to deter police misconduct and protect constitutional rights.

As you might imagine, the exclusionary rule has been unpopular among a lot of people. Over the years, SCOTUS has carved out a number of exceptions to the rule. But the heart of the rule remains intact.

And this concludes our whirlwind tour of warrants!