What constitutes a detention under the Fourth Amendment?

Rather, the seizure of a person - commonly known as a detention - occurs only when the police restrict the person's freedom of movement by means of physical force or a show of authority. (United States v. Mendenhall (1980) 446 U.S. 544, 553.)

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"So long as a reasonable person would feel free 'to disregard the police and go about his business,' [citation] the encounter is consensual and no reasonable suspicion is required. The encounter will not trigger Fourth Amendment scrutiny unless it loses its consensual nature." (Florida v. Bostick, supra, 501 U.S. at p. 431.) On review, we must "consider all the circumstances surrounding the encounter to determine whether the police conduct would have communicated to a reasonable person that the person was not free to decline the officer's requests or otherwise terminate the encounter." (Id. at p. 439.)