What constitutes a search and seizure under the Fourth Amendment?

to commit a crime.' . . . Third, and finally, there are those seizures of an individual which exceed the permissible limits of a detention, seizures which include formal arrests and restraints on an individual's liberty which are comparable to an arrest, and which are constitutionally permissible only if the police have probable cause to arrest the individual for a crime." ' " [Citation.] [] As the United States Supreme Court explained in Florida v. Royer (1983) 460 U.S. 491: '[L]aw enforcement officers do not violate the Fourth Amendment by merely approaching an individual on the street or in another public place, by asking him if he is willing to answer some questions, by putting questions to him if the person is willing to listen, or by offering in evidence in a criminal prosecution his voluntary answers to such questions. [Citations.] Nor would the fact that the officer identifies himself as a police officer, without more, convert the encounter into a seizure requiring some level of objective justification. [Citation.] The person approached, however, need not answer any question put to him; indeed, he may decline to listen to the questions at all and may go on his way. [Citations.] He may not be detained even momentarily without reasonable, objective grounds for doing so; and his refusal to listen or answer does not, without more, furnish those grounds. [Citation.] If there is no detentionno seizure within the meaning of the Fourth Amendmentthen no constitutional rights have been infringed.' [Citation.] Under case law established by the high court, ' " '[A] person has been "seized" within the meaning of the Fourth Amendment only if, in view of all the circumstances surrounding the incident, a reasonable person would have believed that he was not free to leave.' " ' " (People v. Hughes (2002) 27 Cal.4th 287, 327-328.)