When a person is stopped either in a car, on foot or bike by any state or federal law enforcement officer such stop must meet certain legal criteria established by relevant case law.
generally, the officers must have probable casue to stop a motorist. For instance, an improper change of lane, broken tail light, obscured license plate, objects protruding dangerously from the car etc. may give a reasonablerise to such a lawful stop on the road.
Additionally, if a law enforcement officer develops an articulable reasonable suspision, he or she may also stop a person for a quick field interview. A bulging object resembling a weapon, or a suspicious behavior (peering in an open window at night) may alert such officer that something suspisious taking place. In both instances above a search warrant is not required.
2. Scope of interview
Any probable cause traffic stop may be either brief or very protracted. If a violation is minor, a citation is issued and the motorist is free to go, however, if the stop leads to more items discovered ( an open view alcohol container, weapon displayed, odor of marijuana in the car sedan etc.) a police officer may further investigate and interview the motorist. At this time, the motorist is deemed briefly stopped and not under an arrest, therefore, there is no Miranda warning requirement attaches to this consensual voluntary communication between the officer and motorist.
There are some essential differences between federal officers and state police. For one, a federal officer may inquire in a status of any lawfully stopped person, a police officer may not so unless the local jurisdiction permits it, like the newly enacted Arizona law to become effective July 29, 2010.
Additionally, if one lies to a federal agent additional charges of perjury may be brought against a person.
Additional resources provided by the author
For any additional guidance, review Terry stops, consensual search and consensual interview and the new Arizona law.