What is the test for a motion to suppress evidence that was first brought at the preliminary hearing?

In reviewing a ruling on a motion to suppress evidence that was first brought at the preliminary hearing, as was done in the present case, we defer to the magistrate's factual findings where they are supported by substantial evidence. (People v. Snead (1991) 1 Cal.App.4th 380, 384.) "In determining whether, on the facts so found, the search or seizure was reasonable under the Fourth Amendment, we exercise our independent judgment." (People v. Glaser (1995) 11 Cal.4th 354, 362.)

Not all encounters between police officers and individuals implicate the Fourth Amendment's prohibition of "unreasonable searches and seizures." (Florida v. Royer (1983) 460 U.S. 491, 499.) An officer does not implicate Fourth Amendment concerns "by merely approaching an individual on the street or in another public place, by asking him if he is willing to answer some questions, [or] by putting questions to him if the person is willing to listen." (Id., at p. 497.) An officer may talk to anyone he encounters while regularly performing his duties. (People v. Castanada (1995) 35 Cal.App.4th 1222, 1227.) A consensual encounter is not transformed into a detention when an officer asks for identification or asks questions expressing suspicion about an individual's conduct. (People v. Terrell (1999) 69 Cal.App.4th 1246, 1254; People v. Lopez (1989) 212 Cal.App.3d 289, 293.)