The Fourth Amendment to the U.S. Constitution protects against “unreasonable searches and searches and seizures.” And when police stop a motorist—whether during a routine traffic stop or at a checkpoint—it’s considered a seizure for Fourth Amendment purposes. But the rules that apply to vehicle stops are different than those for other types of searches and seizures. Here are the basics.
Generally, a traffic stop is considered reasonable—and therefore legal—if police:
- have a legitimate reason (called “reasonable suspicion”) for stopping the motorist in the first place, and
- conduct the roadside detention in a reasonable manner.
(Terry v. Ohio, 392 U.S. 1 (1968).) So a defendant challenging the legality of a traffic stop will typically focus on one these two requirements. A defendant who can convince a judge that the police did something wrong might be able to get incriminating evidence thrown out.
Reasonable Suspicion Requirement
An officer generally can’t lawfully stop a vehicle without having a reasonable suspicion (also called “reasonable cause”) that the driver or someone else in the vehicle has broken the law. “Reasonable suspicion” means an objectively reasonable basis—it must be more than just a hunch.
Example: While on patrol, Officer Barney spots Raymond zigzagging down the highway at 25 miles per hour, less than half the speed limit. Officer Barney suspects that Raymond is driving under the influence (DUI) of drugs or alcohol. Based on Raymond’s driving pattern and unusually slow speed, Officer Barney has reasonable cause to pull Raymond over.
Example: Roland, who is new in town, is cruising down Main Street in his VW bus. Roland’s psychedelic paint job and long hair catch Sergeant Blingo's eye right away. Though Sergeant Blingo hasn’t actually observed anything illegal, he has a feeling that Roland is up to no good. Sergeant Blingo decides to stop Roland to investigate. Because there’s no objective basis to believe Roland has broken the law, the stop is illegal. An officer having a “feeling” that someone has committed a crime isn’t enough.
Manner of the Detention
Even when an officer has a legitimate reason for pulling someone over, there can still be legal issues with how the officer conducts the stop. The idea is that the detention shouldn’t be any more invasive or time-consuming than reasonably necessary to complete the traffic stop. What’s reasonable depends on the circumstances, including the reason for the stop.
Example: Ziggy gets stopped by Officer James for running a stop sign. After writing a citation, Officer James asks Ziggy if he’d mind sticking around for a while longer. Officer James explains that he’d like to have a canine unit come down and sniff Ziggy’s car for drugs. Ziggy objects because he’s already late for work. Officer James makes Ziggy wait anyway. When the drug-sniffing dog arrives 30 minutes later, it alerts Officer James to drugs in Ziggy’s trunk.
A judge is likely to find the detention was illegal, and the drugs inadmissible in court. Officer James made Ziggy wait for an extended period of time after completing the traffic stop. The reason for the delay—investigating for drugs—had nothing to do with the stop-sign violation that Ziggy was stopped for. And, prior to the dog’s arrival, Officer James had no reason to believe Ziggy had drugs in his car.
Roadblocks and Checkpoints
Police use checkpoints (also called “roadblocks”) for various purposes—DUI and immigration enforcement being the most common. But all checkpoints have one thing in common: law enforcement officers stopping vehicles without reasonable suspicion of criminal activity. So how then are checkpoints legal? The courts have basically said that—in certain circumstances—the government’s interest in having a checkpoint outweighs the inconvenience to motorists.
However, checkpoints aren’t always legal. For instance, the Supreme Court has said that checkpoints set up to uncover evidence of “ordinary criminal wrongdoing” are impermissible. (City of Indianapolis v. Edmond, 531 U.S. 32 (2000).) In determining legalities of a checkpoint, a court might look to:
- the importance of the government interests served by the checkpoint
- the degree to which the checkpoint serves the government interests, and
- the severity of the intrusion and inconvenience to motorists.
(Illinois v. Lidster, 540 U.S. 419 (2004).)