Whether the agents' initial approach, requests for identification and a ticket, and brief questions in the airport concourse constituted a Fourth Amendment seizure.
Holding
No, in Justice Stewart's plurality opinion, the initial concourse encounter was not a seizure because a reasonable person in Mendenhall's position would have felt free to leave.
Reasoning
A person is seized only when an officer uses physical force or a show of authority to restrain that person's freedom of movement. The governing objective question is whether, considering all the circumstances, a reasonable person would believe that she was not free to leave. Police may approach people and ask questions without Fourth Amendment justification so long as the person remains free to disregard the questions and walk away.
The plurality identified circumstances that can convert an encounter into a seizure: several officers acting threateningly, displayed weapons, physical touching, or language or a tone indicating that compliance is compelled. Without such indicia, an otherwise ordinary encounter between an officer and a member of the public does not become a seizure merely because the officer asks questions.
Here, the agents approached Mendenhall in a public concourse, wore no uniforms, displayed no weapons, did not touch her, and requested rather than demanded her ticket and identification. Nothing in the record objectively indicated that she could not end the conversation and continue on her way. The agents' uncommunicated intention to stop her if she tried to leave did not matter because it was not conveyed to her.
This conclusion was not a majority holding of the Court. Justice Powell, joined by the Chief Justice and Justice Blackmun, declined to decide whether the initial encounter was a seizure and instead concluded that reasonable suspicion would have justified it.