In California, only a marked vehicle can legally conduct a traffic stop. A marked vehicle doesn't need to be a black & white (specifically, all the CVC requires is markings on both sides and a red light). Note that there are CODE 3 equipped bicycles that can legally be used for traffic stops (i.e. a "POLICE" sticker on both sides and a red light).
So, I don't think an unmarked vehicle could legally be used for a traffic stop, though I suppose they are, on occasion, in unusual circumstances.
There is no legal requirement for the driver of a marked law enforcement vehicle to be in uniform, although this may be covered under the department's policy.
Although crimes involving impersonation of a peace officer certainly occur, fortunately in the U.S. they are rare enough that I don't think it would be a legal defense for failing to yield on a traffic stop involving a marked vehicle.
For an unmarked or plainclothes stop, I think some good, defensible strategies would be:
- Activating hazard lights and driving slowly to a well-lit, public place;
- Refusing to roll down the windows more than a crack, giving ID, and requesting a marked unit with a uniformed officer be dispatched;
- Using a cell phone to call 911 and verify that the officer conducting a traffic stop is legitimate.
There is no provision in the California Vehicle Code for driving a unmarked vehicle without license plates, regardless of agency, as far as I know.
The overwhelming majority of traffic stops are conducted by duly appointed public officials in the lawful execution of their duties, so I think it is unreasonable to assume otherwise. Evasion is not an acceptable strategy under these circumstances. Keep your mouth shut, use common sense, cooperate and be observant. If there is an abuse, consider it a money-making opportunity...
Last edited by R1145; November 6, 2011 at 04:20 PM.