There are several circumstances that allow police to lawfully stop a vehicle. Police can detain a vehicle with reasonable suspicion that the driver has broken the law. And, under certain circumstances, police can stop a vehicle at a checkpoint, even without evidence of wrongdoing.
Assuming police lawfully stop a car, when do they have the right to search it? Every situation is different, but some general rules for vehicle searches are discussed below.
(This article is about federal constitutional law as interpreted by the U.S. Supreme Court. Be mindful that your state law might provide greater protections.)
The protections of the Fourth Amendment are based on reasonableness. The Fourth Amendment doesn’t prohibit all police searches, just unreasonable ones. In deciding what’s reasonable, the courts balance the interests at stake: the government’s reason for conducting the search and the degree to which the search interferes with individual rights.
Courts often talk about individual rights in terms of one’s “reasonable expectation of privacy.” Generally, the Fourth Amendment’s protections depend on the degree to which the person has a legitimate expectation of privacy in the place or thing searched.
For instance, according to the Supreme Court, people have a compelling privacy interest in their homes. So, police typically need a warrant to search someone’s house. With a vehicle, on the hand, the Court has said a warrant usually isn’t required; to search a car, an officer needs only probable cause that it contains evidence of criminal activity. (This is sometimes called the “automobile exception” to the warrant rule.) The reasoning is that a person has a diminished privacy interest in a car—as compared to a home—and vehicle mobility makes it impractical for police to obtain a warrant before conducting a search.
Probable cause is a fact-specific determination, so there’s no single rule that applies in all situations. But basically, police must have reasonable grounds to believe there’s incriminating evidence inside the car. Probable cause can come from information police receive before the stop or observations made during the detention.
Example: Officer Chan is on duty in an area known for narcotics activity. While sitting in his unmarked car eating a sandwich, Officer Chan sees a vehicle pull up to the corner in front of him. As the vehicle stops at the curb, a man approaches the passenger-side window and says: “What are you looking for?” The driver then responds, “two grams.” The man hands the driver two small baggies and the driver gives him a wad of bills in return. Officer Chan stops the motorist a few blocks down. After having the motorists step out of the vehicle, Officer Chan finds two gram of heroin in the center console. Officer Chan had probable cause to stop and search the vehicle based on what he observed and heard while sitting in his car at curbside.
Example: Detective Waylon stops Jimmy for running a red light. While he’s writing Jimmy a ticket, Detective Waylon smells marijuana and notices what appear to be baggies and a scale on the backseat. Detective Waylon puts Jimmy in the back of his police cruiser and searches Jimmy’s car. Inside the trunk, Waylon finds a pound of marijuana. Detective Waylon had likely had probable cause to search the car based on his observations during the traffic stop.
Normally police need probable cause to search an automobile. But there are a number of exceptions.
Police can search a car without probable cause if the driver gives permission. However, consent is valid only if the driver gives it voluntarily. In other words, police aren’t supposed to threaten or coerce the motorist into agreeing to a search.
Example: Mike gets stopped by Officer Diggins for speeding. Officer Diggins writes Mike a ticket and then pulls his service weapon out of its holster. With his gun pointed in Mike’s direction, Officer Diggins says, “It’s okay if I search your car, right?” Mike doesn’t think twice—he agrees right away. While searching the trunk, Officer Diggins finds LSD. Mike’s consent was invalid because Officer Diggins’ actions were clearly coercive; the search was therefore illegal.
Another exception to the probable cause rule can come into play when police arrest a driver or passenger. However, an arrest doesn’t always give police unlimited authority to rifle through the whole car. A search “incident to arrest” is valid only to the extent necessary to:
And there’s a related rule that restricts an otherwise permissible search to just those areas of the car that could contain the weapon or evidence sought. For instances, if police are looking for a stolen bike, it probably wouldn’t be reasonable to search a glove box. But if they’re on the hunt for something small like drugs, a more thorough search would be justified.
Example: Rodney was pulled over and arrested for driving on a suspended license. Police handcuffed him and locked him in the back of the patrol car. Police then returned to Rodney’s car and conducted a search. Inside the car, police found a bag of cocaine. The search was illegal. Rodney was locked in the police car, so officer safety wasn’t an issue. (There’s no way he could have grabbed a weapon from his vehicle.) And police had no reason to believe that in searching the car they’d find evidence related the arrest offense, driving on a suspended license.
Sometimes a traffic stop leads to an arrest. When this occurs, and no one is there to take control of the vehicle, police usually have the vehicle towed to an impound lot. Generally, police are allowed to conduct an “inventory” search of a lawfully impounded vehicle. But the purpose of an inventory search isn’t to rummage for incriminating evidence. Police are allowed to do these searches so that they can:
If, however, police happen to find evidence of criminal activity during a legitimate inventory search, it can usually be used against the defendant in court.
