Our criminal procedural class in law school was getting tired of the Fourth Amendment — the one that protects “persons, houses, papers, and effects against unreasonable searches and seizures” and requires warrants based on probable cause before the police can look for evidence.

One of my classmates had had enough. She felt that all of this was silly. These rules, exceptions, and exceptions to exceptions were pointless. The police got the evidence. The guy is guilty. And now we can’t use it? He’s freed on a technicality. Is that really how we should look at this?

The exclusionary rule means that when the police or other law enforcement officers violate someone’s constitutional rights, then prosecutors cannot use that evidence gathered as a result of that violation against the person.

That’s the exclusionary rule. And it still manages to upset people.

Some feel that crime is so rampant and so egregious that we’re hindering police efforts to reduce it.

That’s what frustrated my classmate so much. The exclusionary rule can be devastating to the prosecution’s case. Strong, incriminating evidence just vanishes. Why have such a rule?

It wasn’t always this way. In the early decades of the 20th century, state police forces didn’t have to abide by the exclusionary rule, only federal agents in federal court. 

Think about those old detective novels and movies. The cops burst into a smoky room where gangsters are counting money or doing something illegal, a detective punches someone in the face, and the case is closed.

There’s no search warrant. There’s no elaborate way to, as Sen. Kurt Fevella recently put it, “figure out a way so we can break legs.” What’s the big deal?

Consider the case that put the exclusionary rule on the map.

The defendant was a difficult, strong-willed woman — and that’s how her loved ones described her.

In 1957, the Mississippi native Dollree Mapp moved to Cleveland, Ohio, divorced from an abusive boxer husband and living with her daughter.

Then the police came over. Someone tried to blow up Don King’s house (yeah, the same guy made famous for promoting Mike Tyson in the 1980s and ‘90s) and suspected Mapp was hiding the bomber in her home. They demanded entry to search the house. Mapp called her lawyer, who advised her not to let them in without a warrant. She did just that and the police left.

More officers returned hours later. A lieutenant waved a piece of paper at her and said it was a warrant. Mapp demanded to see it. The lieutenant refused.

Not taking no for an answer, she grabbed the paper from him and stuffed it into her blouse. Such a bold move from a woman of color must have surprised the police. One of them asked, “what do we do now?”

An officer stepped forward and announced he was “going down after it,” struggled with Mapp, and reached into her blouse to get the paper back. She never got to read it. No one did.

The police handcuffed Mapp, went into her house and sure enough found the suspect hiding in her house. But they didn’t leave. They searched every room and opened every box and drawer. They found books and nude sketches considered obscene. Although Mapp told them that they belonged to a long-gone lodger, she was arrested for possessing obscene material — a felony in 1957.

It took the jury 20 minutes to convict her. The judge sentenced her to up to seven years in prison.

The suspect, by the way, was cleared of bombing King’s house.

Mapp appealed her sentence and lost in the Ohio courts. It was far from surprising. As one professor later wrote, what the police did was “nothing extraordinary; it was an everyday fact of life for blacks and other racial minorities. Police throughout America were part of the machinery of keeping blacks ‘in their place,’ ignoring constitutional guarantees against unreasonable arrests and searches and those that barred the use of ‘third-degree’ tactics when questioning suspects.”

But Mapp persisted and appealed to the U.S. Supreme Court. Her case made history. In 1961, the Supreme Court held for the first time that the states were obligated to enforce the exclusionary rule against local police. It would not be limited to federal courts anymore.

The Supreme Court explained that “the right to be secure against rude invasions of privacy by state officers is . . . constitutional in origin” and “we can no longer permit that right to remain an empty promise.” It is not “revocable at the whim of any police officer who, in the name of law enforcement itself, chooses to suspend” the Fourth Amendment.

Of course, that was Earl Warren’s Supreme Court, and the justices changed the way police investigate crime and the way we prosecute people. It was before the conservative backlash led by William Rehnquist and decades of Supreme Court justices who have watered down the exclusionary rule and made it a difficult doctrine to understand.

And while the erosion has been accelerating for generations in federal court, the exclusionary rule is strong in Hawaii. The Hawaii Supreme Court recognizes the need to deter police misconduct while investigating crime and even goes a step further.

The state Supreme Court has also made it clear that trial courts cannot allow tainted evidence to be used as a matter of principle.

It means the courts should not give prosecutors a pass for using tainted evidence. If the guilty go free because our law enforcement violated the law, the exclusionary rule says so be it. As Justice Sonya Sotomayor wrote, “when courts admit illegally obtained evidence as well, they reward manifest neglect if not an open defiance of the prohibitions of the Constitution.”

So going back to my classmate’s complaint. Freed on a technicality? No way. The Fourth Amendment isn’t just a technicality. And is this how we should look at it? Absolutely.