Criminal Procedure

A frisk without probable cause

A Cleveland detective named McFadden watched three men in front of Zucker’s store and read what he saw as the run-up to a stickup. He walked over, identified himself, and asked their names. Nothing they said changed his mind, so he turned John Terry around and patted the outside of his overcoat. He felt a pistol in the left breast pocket and could not work it loose with the coat on. So he moved all three men inside the store, pulled the coat off, and drew out a .38-caliber revolver.

At the suppression hearing the trial judge threw out the government’s theory of the case. Calling this a search incident to a lawful arrest, he said, would be “stretching the facts beyond reasonable comprehension,” because McFadden had no probable cause to arrest anybody before he started patting. The revolvers came in anyway. That gap, between what an officer may do and what would have justified an arrest, is where criminal procedure lives. It opens at the first contact and stays open through trial. This reading walks it in order, so that when the activity hands you six encounters and a confident AI tutor, you already know which question comes first.

The two standards that do the street-level work are probable cause and reasonable suspicion, and they are not the same size. Probable cause is what an arrest and most warrants require: a fair probability, read from the facts, that a crime occurred or that evidence sits where the officer wants to look. Reasonable suspicion is lower. It asks for specific, articulable facts pointing to criminal activity, and it buys a brief stop and nothing resembling an arrest.

Terry v. Ohio (opens in a new tab) fitted those two together into the doctrine now called stop and frisk. An officer with reasonable suspicion may stop a person briefly to investigate. If the officer also reasonably suspects that person is armed and dangerous, the officer may pat down outer clothing for weapons. McFadden’s own testimony shows the limit built into that second step. He said he patted the men only to learn whether they were carrying, and he kept his hands outside their coats until he felt the guns. The frisk answers one question. A pat-down that keeps going after that question is answered has turned into a search nobody authorized.

The same logic caps how long a stop may run. In Rodriguez v. United States (opens in a new tab), an officer finished writing a warning ticket and then held the driver while a drug dog worked the car. Authority for the seizure ends, the Court said, when the tasks tied to the traffic violation are completed or reasonably should have been. A dog sniff is not one of those tasks, because it hunts for ordinary criminal wrongdoing instead of serving road safety. Finishing the traffic work quickly does not bank an officer extra minutes for something else.

When watching becomes searching

Everything above assumed a search or a seizure had already happened. Often the harder question comes earlier: whether the Fourth Amendment is in the room at all. Point a camera down a public street and you have searched nobody. Open a locked drawer and you plainly have. Most modern fights sit somewhere between those two.

Katz v. United States supplied the test still in use. Government conduct is a search when it invades an expectation of privacy the person actually held and society accepts as reasonable. That is the reasonable expectation of privacy question, and it runs first, because conduct that is not a search never reaches any rule about warrants.

Once conduct is a search, the warrant requirement sets the default: a warrant, supported by probable cause, from a neutral magistrate. In practice the exceptions carry most of the traffic. Consent, exigent circumstances, a search incident to arrest, the automobile exception, and plain view each let an officer proceed without one. So a suppression hearing is seldom an argument about whether the default exists. It is an argument about whether these facts fit an exception.

The hard cases now involve records a company keeps about you. For decades the third-party doctrine held that information you hand to someone else stops being private against the government. Carpenter v. United States refused to apply that reasoning to cell-site location records. Such records give an encyclopedic account of a person’s movements, and they are not truly shared in any ordinary sense. In 2026 Chatrie v. United States (opens in a new tab) carried Carpenter to Google Location History, which fixes a phone’s position every couple of minutes. Police conduct a search, the Court held, when they obtain that history through a geofence warrant.

Notice what that holding settles and what it leaves alone. The Court answered the threshold question and stopped there, returning the case to the Fourth Circuit to decide whether this particular warrant satisfied probable cause and particularity. Ask a model about geofence warrants and it will often skip that seam and report that the Court banned them. It did not. It held that the Fourth Amendment applies, which is where the analysis starts rather than where it ends.

The two words that trigger a warning

Move from the street to the interview room and the governing text changes. The Fifth Amendment (opens in a new tab) says no person shall be compelled in any criminal case to be a witness against himself, and Malloy v. Hogan made that binding on the states. The operative word is compelled. The privilege against self-incrimination is about pressure the government applies, not about a suspect’s later regret at having talked.

Miranda v. Arizona built a warning around the privilege, and the warning is required only where two conditions meet: custody and interrogation. Custody asks whether a reasonable person in that position would have felt free to end the encounter and leave. Interrogation covers direct questioning and anything else the police should know is likely to draw an incriminating response. Neither condition alone sets the requirement off.

Students and language models go wrong here in opposite directions. One treats every police question as interrogation demanding a warning, which would put a recitation on every roadside exchange. The other treats one sentence at the start, telling someone he is free to go, as fixing his status for the whole encounter. It does not matter, on that view, how long the questioning runs or what the room feels like by the end. Custody is measured by the circumstances as they actually were, which means the answer can change partway through.

Who stands beside you, and who decides

By the time a case reaches a courtroom the Sixth Amendment carries most of the load, and the right to counsel and to a jury is two guarantees with separate histories. Clarence Gideon was charged in a Florida court with breaking and entering a poolroom, a felony under Florida law. He appeared without funds and without a lawyer, asked the judge to appoint one, and was turned down. Gideon v. Wainwright made appointed counsel for indigent felony defendants binding on the states.

Nine years later Argersinger v. Hamlin moved the line off the felony label, in another case out of Florida. Argersinger was indigent, charged with carrying a concealed weapon, an offense carrying up to six months. He was tried to a judge without a lawyer and sentenced to ninety days in jail. The question, the Court held, is not how a state files the offense. It is whether the defendant ends up locked up.

The jury right traveled the same road. Duncan v. Louisiana incorporated it against the states, so a state defendant facing a serious offense is entitled to a jury. Williams v. Florida then held that twelve jurors are not constitutionally required and that six can do the work. Kian v. Florida puts that number back in front of the Court, in a case asking whether someone charged with a serious felony may be tried by six.

The edges of these rights are still being drawn. A defendant who takes the stand keeps his right to counsel, and he also takes on a witness’s duty to give testimony that is his own rather than his lawyer’s. When a trial recesses in the middle of that testimony, the two pull against each other, and the answer has turned on how long the break runs and how much the judge actually forbids.

The remedy that makes the rest of it real

A rule without a remedy is advice. The exclusionary rule is what gives the Fourth Amendment teeth inside a criminal case: evidence obtained in violation of it is generally kept out, and Mapp v. Ohio applied that rule to the states. It appears nowhere in the constitutional text. The Court built it to deter police misconduct, and because deterrence is the reason for it, the Court has carved exceptions where deterrence would gain nothing, good faith among them.

That is why the remedy belongs at the end of an analysis rather than in place of one. A violation does not erase a conviction by itself. It keeps particular evidence out, at a suppression hearing, usually before trial, and the prosecution continues without that evidence or collapses for want of it. McFadden’s frisk is the clean illustration. The judge found no probable cause to arrest, upheld the pat-down anyway, and let the revolvers in.

So run the sequence in order. Which amendment governs this moment. What standard it sets. How that standard comes out on these facts. What a court would actually do about it. The activity gives you six encounters and an AI tutor built to walk that sequence beside you, and your work is to check its work. The Encounter Analyzer will get most of the framework right, which is exactly what makes its errors hard to see. Watch for three habits: a famous case named where a narrower one controls, a rule stated without its qualification, and an open question answered as if the facts settled it. The last one is the costliest. When a fact is missing, you need the model to say so.