Getting pulled over can feel stressful, even if you believe you’ve done nothing wrong. While most traffic stops end with a warning or a ticket, some escalate into a vehicle search. You might wonder how police officers decide they have the right to perform a warrantless search during an otherwise routine traffic stop. Here are a few ways officers interpret the term “signs of illegal activity.”

In my state of Ohio, like in most states, police need “probable cause” to search a vehicle without the driver’s permission. Probable cause means they must observe something that “reasonably” suggests illegal activity. Of course, this can lead to relative application. In other words, some officers will act on what they see as a sign of illegal activity while others, when presented with the same scenario, might just move on with their day. Still, sources like the Office of the Ohio Public Defender point out when trained officers acted on specific (read: unique) indicators that held up in court.

Police might flag the following as “signs of illegal activity”:

• Unusual behavior
• Smells or sounds
• Illegal substances, contraband, or items related to “crime” in plain sight
• Conflicting stories
• “Prior knowledge” or alerts

Police pay attention to how you act. If the driver appears extremely nervous—beyond what’s typical for a traffic stop—it might raise suspicion. Avoiding eye contact, shaking hands, or overly defensive behavior can influence an officer to look closer.

If the officer smells something illegal, like marijuana or alcohol (especially if you’re underage or it’s open), that alone can justify a search. The same goes for unusual sounds which might suggest hidden items or activity.

Anything illegal in plain view gives an officer probable cause. This could be drugs, open containers of alcohol, or even drug paraphernalia. If it’s visible through the window or when you open the glove box, the officer can legally proceed with a search.

If passengers in the car give different answers to the same question, officers may suspect something is wrong. They often ask basic questions like “Where are you headed?” to gauge consistency.

Some objects, like large amounts of cash and packages or baggies, can suggest illegal activity. Officers look for these when questioning occupants or glancing into the car.

If the officer has prior information about the driver, such as an active warrant, or a drug-sniffing dog alerts them during the stop, they can search your car.

In a vacuum, certain signs might not lead to a warrantless search. Collectively, though, stacked indicators might allow “probable cause” to hold up in court.

Once a police officer has “justifiable” probable cause, they can search any and all vehicle compartments without a warrant. This includes the glove box, trunk, and everywhere else. Depending on the circumstances, officers might also search inside a vehicle’s contents, meaning they’ll open and look in containers, bags, boxes, and so on.

In Ohio, courts regularly uphold searches based on these factors under state law and the Fourth Amendment. However, officers must articulate their reasons for the vehicle search clearly. If you feel a search was unjustified, you can challenge it in court later.