The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated, and no Warrants shall issue, but upon probable cause, supported by Oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized.

The Fourth Amendment to the Constitution places limits on when the police can seize or detain any person in the United States. The Supreme Court of the United States has ruled that all seizures must be reasonable to be lawful.

There are some myths out there. One is that if the police have not arrested you, then you are free to leave. That's not always the case. While you can tell an officer to charge you or release you, it's not always the wisest course of action.

To describe the control that the police may exercise over a person and the level of evidence that the police must have, many courts refer to the three tiers of police citizen contact.

Tier 1 - Voluntary Police Citizen Contact

The police are people, and any person may approach any other person and engage them in a conversation. So can the police. It doesn't require any level of suspicion. An officer can say hello, ask you for your name or your identification, inquire into your activities, and even ask to search you. Many people might not want to stand and talk to the officer, but most people do. Firstly, it's not polite to just walk away from someone who's talking to you. There's also the perceived authority of an officer. As long as the officer doesn't coerce you to stay it's still a voluntary contact.

Officer Jones sees Mark's vehicle leave a bar. There's nothing illegal about driving away from a bar, but she decides to follow the car anyway to see if the driver has any trouble. Before she sees any erratic driving, the vehicle pulls into a hotel and parks. Officer Jones parks nearby approaches Mark as he's walking to the hotel lobby. Officer Jones asks him where he's going, and he says that he's returning to his hotel room for the night. Officer Jones asks Mark for his license, which he has no obligation to provide, but he complies with her request. While he's searching through his wallet, she asks him some other questions. He doesn't seem to be able to answer questions and search for his identification at the same time. While they're talking, he admits to drinking two beers, and Officer Jones notices the odor of an alcoholic beverage coming from the driver.

This voluntary police-citizen contact may lead to Mark's arrest for driving under the influence of alcohol. As long as the Officer Jones doesn't force Mark to do anything, and Mark is free to leave, it's still a Tier 1 encounter.

Tier 2 - Investigative Detention

Officers may detain someone without arresting them based on reasonable suspicion. That is where a police officer 'observes unusual conduct which leads him reasonably to conclude in light of his experience that criminal activity may be afoot'¹; the officer may detain that person while he either confirms or dismisses those suspicions. The officer can question the person about his identity and activities. After a brief detention, the officer must release the person if there is insufficient evidence to make an arrest.

During an investigative detention, if the officer has reasonable suspicion to believe that you are armed and dangerous, the officer may search your outer clothing to locate weapons. This is commonly referred to as a 'Terry pat'.

This is all based on the Supreme Court Decision, Terry v. Ohio, 392 U.S. 1 (1968). In that case, Detective McFadden was a veteran cop with 39 years of experience. He watched two men, one of who was Terry, in a downtown business district. One of the men would walk down the street, look in a store window, and then return to the other man. They'd talk and then the other guy would do the same thing. This went on for a period of time, and the two men were joined by a third. Detective McFadden believed that they were casing the place for a robbery. Eventually, Detective McFadden approached the men, searched their outer clothing for weapons, and located guns on two of them. Terry and one of the other men were arrested for carrying concealed weapons.

Several things can come into play during this detention.

First off, there's the issue of identification. Some but not all states require that a person identify themselves when questioned by the police.

As for further questioning, there is a Fifth Amendment right to remain silent. You don't have to speak to the police about what you are doing. However, there may be circumstances where your activities are enough to provoke an arrest for loitering or some other offense. Investigative detention is not an arrest, so Miranda warnings do not have to be given prior to questioning.

During a pat down search, any contraband that the officer feels and recognizes during the pat down may be seized as evidence. It's not important that the contraband is not related to the reason for the Terry Pat.

The length of detention might vary. Generally, investigative detention is quite brief, perhaps 15-20 minutes. However, the facts may authorize a longer detention. The key is that it must be reasonable to comply with the Fourth Amendment.

Traffic stops are another version of investigative detention. Officers may make stops based on reasonable suspicion. Generally, officers will have probable cause that a traffic violation occurred, so that the officer can write a traffic ticket, but that's not always the case. An officer may observe someone weaving within their lane or driving much slower than the posted speed limits. Those aren't traffic violations, but they are indicators of a person who's driving under the influence of intoxicants.

The traffic stop, even when it's based on probable cause isn't considered an arrest, because the common perception is that a person isn't going to be arrested. Generally, the officer will release the person with a verbal warning or a traffic ticket.

Tier 3 - Custodial Arrests

The final tier of police citizen encounter is a custodial arrest based on probable cause. Probable cause, broadly defined, is the reasonable belief, based on facts, that a crime occurred and that a particular person committed that crime. The arrest is complete when the defendant submits to the authority of the officer. This is generally where the officer handcuffs the offender and puts him in the back of a police car.

When an officer makes an arrest, the officer has the right to search the prisoner and his or her immediate surroundings in the vicinity of the arrest. The purpose of the search is to ensure that the prisoner doesn't have any weapons and to secure any evidence that the person may have. This search isn't limited to just outer clothing like a Terry pat. It may include pockets, shoes, places that people commonly conceal items.

The probable cause to make an arrest need not be something that the officer personally observed. It can be based on collective knowledge of officers.

Exceptions

There are always exceptions that don't fit into this neat three category system of defining police-citizen encounters. Police in many states may use roadblocks to do suspicionless checks for driver's licenses, seatbelt compliance, or sobriety. In order to enter most courthouses, you must submit to some form of search. Also, when you enter the United States, you may be questioned and searched by Customs and Border Protection Officers or Border Patrol Agents.

So What do I do With This Information?

If you are dealing with the police, you may want to clarify where you are. You can do so by asking the officer if you're free to go.

If you think the police are going too far, there are steps you can take. You may exert your rights. You do not have to consent to a search when asked. If you object, you should state your objection clearly. However, the officer may believe that he has enough to compel a search. If the officer is going to conduct a search anyway, it is best to submit and sort it out later in court or through the agency's complaint process. Physically resisting a police officer is a crime², and the officer will use force to overcome your resistance.

The reasonableness of police actions is based on what the officer reasonably believes at the time. It is possible that the officer has information that you are not aware of. For instance, you might be detained because you closely match the description from a crime that has just occured. You may have done it or you may be an innocent party. It may take a few minutes for the officer to sort things out.

Reasonableness, in accordance with the Fourth Amendment, is the key to many aspects of officer conduct. It governs what the police are legally allowed to do when they limit your freedom. The three tiers of police-citizen contact provide guidelines that the courts use to judge the lawfulness of law enforcement encounters.