While police generally need a warrant to search you or your property — during a traffic stop, police only need probable cause to legally search your vehicle. Probable cause means police must have some facts or evidence to believe you’re involved in criminal activity.
In other words, an officer’s hunch without evidence of illegal activity is not enough to legally search your car. Before searching, he must observe something real. Common examples of probable cause include the sight or smell of contraband in plain view or plain smell, or an admission of guilt for a specific crime. The presentation of any of these facts would allow an officer to perform a search and make an arrest.
Be aware that minor traffic violations (e.g. speeding, broken tail-light, or expired registration) are not considered probable cause.
Okay. So how can I keep police from searching my car?
Simply understanding the legal definition of probable cause probably won’t be enough to prepare you for the pressure and confusion of a real police encounter.
Most police are able to exploit a major loophole to the probable cause search requirement. But by following these basic rules, you’ll be better able to prevent police from tricking you into giving up your your constitutional rights. You’ll also improve your odds of driving away safely.