The bottom line is going to be whether the officer had a reasonable suspicion that you were violating the law prior to the stop--that is the standard for a valid investigatory stop. Whether the officer issues you a warning or issues you an actual citation charging you with an offense, this standard must still be met. Unless he can testify that you had a rear light defect under California law, it would not appear that he had this reasonable suspicion. Not that he would have to charge you with it, but did he actually cite you for any kind of a rear light defect?

