3.2 Fourth Amendment Stops, Searches, and Probable Cause

Fourth Amendment Decision Ladder

The Fourth Amendment and Texas Constitution Article I Section 9 protect against unreasonable searches and seizures. The BPOC unit does not ask cadets to recite case names. It asks them to articulate the legal basis for a stop, decide whether facts support an investigative detention, and decide whether probable cause supports arrest or search. The cleanest way to remember the suspicion levels is a tier list:

• No suspicion → consensual contact only (the person is free to leave; no restraint by authority).
• Reasonable suspicion → brief investigative detention (a Terry-style stop based on specific, articulable facts that crime is afoot).
• Reasonable suspicion of a weapon → a protective frisk (a limited pat of the outer clothing for weapons only).
• Probable cause → arrest, or a warrantless vehicle search of areas where evidence of the offense could be.

An exam prompt usually gives mixed facts. A person near a closed business is not enough by itself. A matching suspect description, a late hour, a prior burglary pattern, visible property, inconsistent explanations, or evidence in plain view may change the analysis. Write the answer from facts to authority, never from the desired result backward.

Reasonable suspicion is lower than probable cause, but it still requires a real factual basis judged by the totality of the circumstances. The BPOC racial-profiling scenario warns against stopping a person because they seem "out of place." If the prompt offers only race, ethnicity, national origin, or vague unease, the correct answer is usually that the detention lacks lawful support.

Scenario guidance

For a suspicious-vehicle call, first list what the complainant reported: vehicle description, plate state, person description, broken lock, willingness to prosecute. When the officer later sees a similar car after hours at a recently burglarized business, list the matching facts before deciding to detain. If jewelry, watches, and loose change are then seen in plain view, explain how those new observations push reasonable suspicion toward probable cause for arrest or a vehicle search.

Separate the stop from the search. Blocking a vehicle, ordering occupants out, frisking, opening containers, and arresting are different intrusions, each needing its own justification. The exam may approve one step and reject the next if the facts do not support escalation.

Exam trap

Do not say probable cause exists just because a person is nervous. Nervousness can be one fact in a totality analysis, but the exam expects time, place, description, offense pattern, observed evidence, statements, and safety concerns combined. Do not confuse a frisk with a full search: a pat-down is a weapons check during a legitimate stop, not a general evidence search triggered merely by detaining someone. Finally, do not treat a consent search as unlimited — consent can be refused, withdrawn, and is bounded by the scope the person actually agreed to.

Warrantless Search Exceptions the Exam Tests

The general rule is that searches require a warrant supported by probable cause and a particular description of the place and items. The exam then tests the recognized exceptions to that warrant requirement. Know each by name and by trigger:

• Search incident to a lawful arrest — after a valid custodial arrest, the officer may search the arrestee and the area within immediate reach for weapons and evidence.
• Automobile exception — with probable cause that a vehicle contains evidence of a crime, an officer may search the parts of the vehicle and containers where that evidence could be, without a warrant, because vehicles are mobile.
• Consent — a voluntary, knowing agreement; the person may limit or withdraw it, and silence is not consent.
• Plain view — an officer lawfully present may seize an item whose incriminating nature is immediately apparent.
• Exigent circumstances — hot pursuit, imminent destruction of evidence, or an emergency threat to life can justify immediate entry.
• Inventory — a routine, policy-driven catalog of a lawfully impounded vehicle's contents, done to protect property, not to hunt for evidence.
• Protective frisk — the limited weapons pat-down already covered above.

Worked example

An officer makes a lawful traffic stop for an expired registration, smells nothing and sees nothing illegal, and the driver politely declines a search request. The driver is not arrested. Which exception applies? None. There is no arrest (so no search incident), no probable cause tied to the car (no automobile exception), no consent (it was refused), nothing in plain view, and no emergency. The correct exam answer is that the officer may not search. Change one fact — a baggie of suspected narcotics visible on the console — and now plain view plus the automobile exception can support a search.

The exam rewards spotting which single fact unlocks an exception, and which absent fact keeps the warrant requirement in force.