The Fourth Amendment to the United States Constitution prohibits warrantless searches and seizures, rendering them per se unreasonable unless an exception to the warrant requirement applies. However, not all interactions between individuals and the police constitute a seizure.
Interactions between citizens and the police can fall within three distinct categories: a consensual encounter, an investigatory stop and an arrest.
What is a consensual encounter?
A consensual encounter occurs when the police simply approach a person in a public place and engage the person in conversation, and the person remains free not to answer and to walk away.
When does a consensual encounter become an investigatory stop?
A person is subject to an investigatory stop when, in view of all the circumstances surrounding his or her encounter with the police, including police use of physical force or display of authority, a reasonable person would have believed that he was not free to leave or is compelled to respond to questions.
What information do the police need in order to conduct an investigatory stop?
To conduct an investigatory stop the police must have a reasonable, articulable suspicion that the individual they are detaining is engaged in criminal activity.
How do courts determine whether reasonable suspicion exists?
Courts examine the totality of the circumstances and objectively evaluate whether the officer had a particularized and reasonable basis for suspecting that an individual was involved in criminal activity. However, a mere suspicion or hunch of criminal activity which is not supported by specific and articulable facts is an insufficient basis upon which to make an investigatory stop.
Reasonable suspicion to conduct an investigatory stop can be based upon a tip to law enforcement, law enforcement observations, or a combination of the two. A citizen tip may be an independent basis for an investigatory stop if it is reliable and communicates information to law enforcement that provides facts constituting a reasonable suspicion of criminal activity.
How does this apply in the real world?
The police can stop a person as they are walking down the street and engage them in conversation. Some courts have even held that a police officer can ask a person for identification during a consensual encounter. However, the police cannot, without reasonable suspicion that a person is engaged in criminal activity, restrain that individual of their liberty so that a reasonable person would no longer feel free to leave. A display of authority that could make a person feel compelled not to leave might include police officers displaying their weapons, using an authoritative tone of voice or language meant to require compliance, touching the person or blocking their path.
Pursuant to their community caretaking function, law enforcement officers can stop someone out of concern for safety, well-being, or to provide help due to an emergency. In this instance, police officers are not required to have reasonable suspicion that the person is engaged in criminal activity but the officer must show that there was a reasonable basis for his belief that he had to act as a caretaker.
If a consensual encounter turns into an investigatory stop the Fourth Amendment reasonableness requirement is implicated.