Police interactions with the public are defined as “mere encounters,” “investigative detentions,” or “arrests.”
Constitutional protections against unreasonable “searches and seizures” extend only to those instances in which a “seizure” of the individual has occurred. A “seizure” occurs only when a reasonable individual would not fee “free to leave.” Any interaction where a reasonable individual would feel free to leave or where the police engage in conduct not amounting to a search, such as observing something in plain sight does not require a legal basis for the police activity.
An interaction during which a reasonable person feels free to leave is a “mere encounter.” Of course,”reasonable” varies a great deal between individuals. In Pennsylvania,a seizure is established whenever the police restrict movement, request identification, or ask about crime or criminal conduct. For example, a safety check or rendering assistance is a mere encounter, not a seizure.
In order for the police to engage in the next level of interaction, the “investigative detention,” there must be a level of articulable reasonable suspicion on the part of the police. Thus, a mere encounter may turn into an “investigative detention” if the police can articulate a level of reasonable suspicion. A circumstance under which this may occur is if an officer stops you and asks for identification. The Superior Court has held that asking for identification creates an investigative detention that must be supported by reasonable suspicion. However, in the everyday course of events, most normal people will not refuse. If you do, the police may detain you until identification can be made. Since this is an inconvenient for which there is usually no vindication unless you are really doing something wrong, I always advise to carry ID. If everything checks out, the police will usually advise that you are “free to leave.” They tell you this because, having no reasonable suspicion, they cannot hold you unless you create another basis for reasonable suspicion. And you must be “free” to create one. Walk away and give them no reason to stop you again.