Among the most common interactions between citizens and police are traffic stops. Many of these are straightforward: a driver is speeding or doesn't heed a traffic signal and receives a citation from a police, sheriff, or CHP officer. Though the driver is irritated and out a few hundred dollars, nothing more serious results.
Some stops go beyond this, though, with charges of more serious crimes. This is where knowledge of probable cause and rules of search and seizure is so important.
Let's say that while driving home one night you're pulled over by your local police. Because of constitutional protections, police can't pull you over, detain you, or question you just because they feel like it. For an officer to initiate a traffic stop, he has to have probable cause, or some evidence that a crime has been, or is being, committed. (See our October 28 post for a general discussion of probable cause.) That means that he has to see you committing a traffic violation - e.g., driving too fast, weaving, rolling through a stop sign - or observe that some equipment on your car, like a brake light, isn't working.
Assume that the police do have probable cause to pull you over - your left front headlight is out - and during the course of this traffic stop, the officer asks for permission to search the car. Do you have to say yes? The short answer is, NO, and we advise clients to politely but clearly state something like, "I do not give my consent to a search of my vehicle." When police lack probable cause to search your vehicle, they must let you go on your way. Moreover, the officer is not allowed to hold your refusal against you.
Under some circumstances, though, police may conduct a vehicle search without your permission and without a warrant.
Though the Fourth Amendment appears to require that police obtain a warrant to conduct a search, the reality is not so simple. A traffic stop is one of those times when police may, depending on the circumstances, conduct a warrantless search.
The law is complex and ever changing on this issue, but there are some key guidelines to keep in mind. In Carroll v. United States (1925) the U.S. Supreme Court established the principle that police may conduct warrantless searches of motor vehicles if probable cause exists that evidence of a crime is present. The justification for this is that since motor vehicles are mobile, evidence could be carried away and disposed of if police were required to go off and ask a judge for a warrant. In California v. Acevedo (1991), the Court extended the scope of searches to include containers in a vehicle, again because the evidence in the container could be driven away and disposed of. Some limits on warrantless searches were articulated by the Court in Arizona v. Gant (2009) when it ruled that once a person has been arrested and moved away from the vehicle, police may not initiate a search unless that search pertains to evidence related to the crime for which the person was arrested. (See our detailed discussion of Arizona v. Gant in our August 23 post.)
The principles to keep in mind are (1) any warrantless search of a vehicle requires probable cause, and (2) without probable cause police must obtain your permission to conduct a search.
