4th Am: Searches — Criminal Law & Constitutional Protections

Officers get an unverified tip that a homeowner is growing marijuana indoors. No warrant. Two of them lead a trained drug dog up the front walkway onto the covered porch, and the dog alerts at the base of the front door. Was that a search?

Yes. Now change one thing. Same tip, same house, but instead they fly over at a lawful altitude and spot the plants in his fenced backyard with the naked eye. Not a search. Same officers, same target, same tip. The Fourth Amendment switches on for one and stays off for the other, and this episode is about where that line runs.

Here is the route. Part one, the threshold question. When does government conduct even count as a search, across the fact patterns the exam loves. Open fields, curtilage, surveillance, technology, false friends, dog sniffs. Part two, the two levels of suspicion. Part three, the searches the government runs with no warrant and often no suspicion at all.

Start with the catch that trips up half the people who miss these questions. The Fourth Amendment is the rulebook for how the government goes looking for evidence, but it only switches on if what the government did counts as a search. Every problem opens with that threshold question.

If the answer is no, the Amendment does not apply at all. No warrant, no probable cause, no suspicion, nothing, and the evidence is fine. Only if the answer is yes do you ask whether the search was reasonable.

There are two independent doorways in, and you need both, because a fact pattern can trigger one without the other. First, the privacy test. Conduct is a search when it invades a reasonable expectation of privacy. The person must actually expect privacy, and society must treat that expectation as reasonable. The second half does almost all the work.

Second, the older trespass test, which the Supreme Court has revived. The government also searches when it physically intrudes on a person, house, papers, or effect to gather information. Attach a tracking device to the underside of a car and officers have occupied an effect to get information.

That is a search on its own. A common mistake is to memorize the famous privacy test and forget that a physical intrusion counts all by itself.

Now the privacy test's big built-in limit. You assume the risk that whatever you reveal to other people ends up in police hands. Three fact patterns come from that, and none of them is a search.

First, false friends. Confide in a companion who turns out to be an informant, or who is secretly recording you or wearing a wire, and that is not a search. You chose whom to trust and took the risk of a disloyal listener.

Second, third-party records. What you voluntarily hand a business carries no expectation of privacy. The numbers you dial. Your bank deposits. Third, abandonment. Trash left at the curb is fair game. Hold that third-party rule loosely, though. Location data is about to carve a hole in it.

Now the ground around the house. The home is the core of Fourth Amendment protection, and it reaches past the four walls to the curtilage. The porch, an attached patio, the fenced backyard where family life spills outdoors. Curtilage gets full, home-level protection.

Land beyond the curtilage gets none. Those are the open fields, unprotected even when privately owned, fenced, and posted.

Try one. A farmer owns eighty acres of woods and pasture behind his house. He fences the parcel, locks the gate, and posts No Trespassing signs every hundred feet. An officer climbs the fence and walks half a mile to a clearing deep in the woods. Search? No. He is a trespasser, but open land is not a house, and society recognizes no privacy expectation out there.

So a fence and a sign do not by themselves convert open fields into protected space. Where is the line? Four factors. Proximity to the home. Whether the area sits inside an enclosure that also surrounds the home. Whether it is used for the intimate activities of home life. And what the resident did to shield it from passersby.

Next, looking. Police do not search when they merely look at what you left exposed. Officers lawfully present may observe evidence in plain view. And the sky is a lawful vantage point. Fly through public navigable airspace, spot cannabis in a backyard with the naked eye, and that is not a search.

Which is our helicopter. The yard was exposed to anyone lawfully flying over. Same for an officer on a public sidewalk glancing through your uncurtained window. What flips looking into a search is enhancement or intrusion. Technology or a trespass, used to learn what plain observation could not.

Which brings us to technology, where the modern action is. Three rules. First, sense-enhancing devices aimed at the home. Police may not use a device not in general public use to detect interior details they could not have learned without going inside.

The classic is a thermal imager aimed at a house to sense the heat of grow lamps. That is a search. You cannot use a gadget to do what would otherwise take a warrant.

Second, tracking and location. Following a car along public roads with an electronic tracker reveals only what any observer could see, so it is not a search. Monitoring an item's location inside a private home is. And physically attaching the tracker is a search under the trespass test.

Third, cell-phone location data, the big modern rule. Your phone constantly generates location records held by your carrier. The Supreme Court held in 2018 that obtaining your historical cell-site records is a search requiring a warrant. The third-party doctrine does not stretch that far.

And it grew. In June 2026 the Court extended that to shorter-term tracking, including geofence data showing which devices were in an area. Carry the safe rule. Acquiring a person's cell-phone location data is a search, and police should get a warrant.

Last in part one, dog sniffs. A sniff disclosing only the presence or absence of contraband is generally not a search. Nobody holds a legitimate privacy interest in contraband, and the sniff exposes nothing else. So a dog around a car during a lawful stop, or around airport luggage, is fine.

But two limits are heavily tested, and our porch is the first. Bringing a drug dog onto curtilage to sniff at the front door is a search. Officers physically intruded on protected space to gather information. A visitor's license to approach and knock does not include bringing a dog.

The second limit is the clock. Test it. A lawful traffic stop is finished, and the officer holds the driver a few extra minutes for the canine unit. Allowed? No. A stop may not be prolonged, even briefly, to run the dog, unless police have independent reasonable suspicion. The sniff is fine only if it adds no time.

Part two. How much justification did the police have? The Amendment bans only unreasonable searches, and reasonableness usually turns on that. The law sorts justification into a ladder, and two rungs do almost all the work.

At the bottom, a hunch, never enough for anything. Then reasonable suspicion, which buys a brief investigative stop and a limited frisk for weapons. Then probable cause, which buys an arrest, a search warrant, and most warrant exceptions. Above those sit the trial burdens, which are not what police need.

Reasonable suspicion is more than a hunch and less than probable cause. The officer must point to specific, articulable facts, not a gut feeling. Those facts, plus the inferences an experienced officer draws, must make it reasonable to suspect criminal activity is afoot. On the totality, never one factor alone.

What adds up? Nervous and evasive behavior. Unprovoked flight in a high-crime area. A detailed tip whose predictions the police corroborate. What usually does not? A bare anonymous tip with no detail and nothing corroborated.

Test it. An officer runs the plate of a passing pickup and learns the registered owner's license is revoked. Nothing suggests anyone else is driving, and the officer sees no traffic violation. Enough to stop the truck? Yes. A specific fact plus a commonsense inference, and the inference need not be the only possibility.

Probable cause is the threshold for an arrest and a search warrant. Do not overstate it. It requires no certainty, and not even a more-likely-than-not showing. It means a fair probability, on the totality, that evidence will be found in the place to be searched, or that this person committed a crime.

On an informant's tip, courts run no rigid checklist. They weigh reliability, basis of knowledge, detail and corroboration together, and weakness in one can be made up by strength in another.

And the standard is objective. The officer's private hunch, good faith or bad, neither creates nor destroys suspicion. So distrust any answer demanding proof, certainty, or that the officer be sure.

Part three. A whole family of searches runs with no warrant and often no suspicion about anyone in particular. Airport screening, sobriety checkpoints, school locker checks, border inspections, booking inventories. Why are those allowed?

Because their primary purpose is something beyond ordinary crime control. Public safety, regulation, protecting students, guarding the border. Courts call that a special need, and when one drives the program the Amendment asks only whether the search is reasonable, balancing interest against intrusion.

And here is the single most important question in this whole area. What is the program's primary purpose? If the true purpose is ordinary crime detection, the special-needs pass evaporates and the normal warrant-and-probable-cause rules snap right back.

Run the categories. Border first. At the international border and its functional equivalents, routine searches require no warrant, no probable cause, no suspicion at all. Only a non-routine, highly intrusive search needs reasonable suspicion. And flag one as unsettled. Whether officers may search a traveler's phone at the border without suspicion is split across the courts.

Inventory searches. Police who lawfully impound a car, or book an arrestee, may list and secure the contents with no warrant and no probable cause. The justification is caretaking, not crime-fighting. But it must follow standardized procedures, not an officer's on-the-spot choices, and it must be a genuine inventory, not an investigation in caretaking clothes.

Airport screening is the textbook administrative search. Compelling special need, screening limited to serving it, travelers on notice and consenting by choosing to fly. The same reasoning covers routine inspections of closely regulated industries.

Checkpoints live or die by purpose. Sobriety checkpoints are constitutional, because keeping drunk drivers off the road is a strong safety interest and a brief, neutral stop is modest. Fixed immigration checkpoints near the border are too. So are information-seeking checkpoints, where police stop motorists for help identifying a suspect in a specific past crime by someone else.

Government workplaces. The government, wearing its employer hat, may search an employee's office, desk or work-issued device with no warrant and no probable cause, for a work-related reason. The search must be reasonable at its inception and reasonable in scope. And whether the employee has any privacy expectation at all depends on the workplace's actual practices and policies.

Public schools last, same shape. A school official needs only reasonable suspicion. Reasonable grounds to believe the search will turn up evidence the student broke a law or school rule. Not a warrant, not probable cause. Justified at its inception, and reasonable in scope given the student's age and sex and the infraction.

Watch how scope scales. A specific, reliable report that a student is selling vape pens from her backpack justifies searching the backpack. That is where the pens would be. The same tip does not justify ordering her to strip. That intrusion is wildly out of proportion, however solid the initial grounds were.

And schools may drug-test students who choose athletics or other competitive extracurriculars, with no individualized suspicion. The special need to deter student drug use, plus the reduced privacy expectation there, makes evenhanded random testing reasonable.

A word on authorities. This episode named no cases, and that was deliberate. The exam gives you a fact pattern and asks what result the rule produces. It will not ask you for case names. Your authority here is the text of the Fourth Amendment itself, which protects persons, houses, papers, and effects, bans only unreasonable searches, and never defines the word search. The courts filled that gap.

If you keep only three things, keep these. The two triggers, privacy and trespass, because either one alone makes a search. Curtilage versus open fields, because it decides the home cases. And primary purpose, because it decides every suspicionless program.

Now the traps, straight from the examiners' favorites. One. Do not skip the threshold question. A favorite wrong answer applies warrant rules to conduct that was never a search. Two. The trespass test is a separate, independent path. Conduct can be a search on physical intrusion alone, and the reverse.

Three. Do not let a fence and a No Trespassing sign fool you. They do not convert open fields into protected space, though they can help show that an enclosed area hugging the home is curtilage. Location and use matter far more than signage.

Four. Do not reflexively say third party, so no search, for modern location tracking. The old rule still governs dialed numbers and bank records, but cell-phone location data is protected, and the Court expanded that in 2026. Five. Contraband-only dog sniffs are not searches, but watch the porch and watch the clock.

Six. Primary purpose decides everything in part three. A program really about catching ordinary criminals fails even when dressed in the language of safety. And seven, suspicionless does not mean standardless. Inventories need standardized procedures, checkpoints need neutral criteria, and a program run on unguided discretion fails.

Time for the quick check, and this one comes straight from the BARGO question bank. City police set up a roadblock and stop every passing car. Officers check each driver briefly and walk a drug-detection dog around every vehicle. The department's own memo states the roadblock's goal was to interdict illegal drugs and catch narcotics offenders generally. A driver whose car the dog alerts on is arrested, and moves to suppress.

Is the drug-interdiction checkpoint constitutional? Option one. Yes, because walking a drug dog around the outside of a stopped car is not a search at all. Option two. No, because a person may not be stopped at a checkpoint without individualized reasonable suspicion. Option three. No, because the checkpoint's primary purpose was ordinary crime detection rather than a special need. Pause here if you want a moment.

The answer is option three. A suspicionless checkpoint lives or dies by its primary purpose. Sobriety, immigration and information-seeking checkpoints survive because their purpose is something other than ordinary crime control. A roadblock aimed at interdicting drugs and catching narcotics offenders is unconstitutional, because there is no special need to justify stopping motorists without suspicion.

Option one is right about the sniff and wrong about the case. The exterior sniff is not a search, but the suspicionless stop of every car is a seizure, and its invalid purpose taints the stop. Option two misstates the rule. Valid checkpoints need no individualized suspicion at all. What dooms this one is the purpose. There are thirty-plus more questions on this topic alone, each option explained like that.

Five things to take away. One. Ask whether a search happened before anything else, because if none did, the Fourth Amendment never applies. Two. Two triggers, and either one alone is enough. An invaded reasonable expectation of privacy, or a physical intrusion on a person, house, papers or effect to gather information.

Three. What you expose is not protected. False friends, dialed numbers, bank records, curbside trash, open fields, and anything visible from a lawful vantage point. But the home's interior, its curtilage, and your phone's location data are.

Four. Reasonable suspicion is specific, articulable facts, and it buys a brief stop and a frisk. Probable cause is a fair probability, and it buys an arrest or a warrant. Neither requires certainty. Five. In a suspicionless program, primary purpose decides everything.

Which is why a dog on the porch is a search and a helicopter overhead is not. Same house, same tip, opposite answers. Next time, Fourth Amendment Seizures and Warrants.

Practice this topic with more than 2,900 exam-style questions, free to start, at nextgenbargo.com. This episode is for education and exam preparation only, not legal advice, and we are not affiliated with or endorsed by the NCBE or any bar examining authority.