You run a stop sign. You see it at the last second, and it’s too late to stop. Fortunately, no one else is at the intersection, so there is no accident. However, a police officer sees you run the sign and pulls you over.
If that officer then asks to search your car, do you have to let them?
You don’t. In some ways, this is similar to when they ask you if they can search your house. You still have a right to say no if you don’t want them to do so.
With a house, though, they often have to get a warrant to enter without your permission. They can also get a warrant to search your car, but do they have to? Not always.
What matters is probable cause. An officer cannot search your car for no reason. The traffic stop was just for running a stop sign. That’s not reason enough to search your car on its own. They need probable cause to override your wishes and carry out the stop.
Probable cause doesn’t take much, though. Maybe the officer thinks that you’re intoxicated and that’s why you ran the stop sign. They see a whiskey bottle in your car. It’s an old one that you were taking in to recycle, but the officer may say they think you were drinking it while driving. That may be all it takes to start a search and even make an arrest.
Just getting arrested doesn’t mean you actually did anything wrong, of course. Make sure you know what rights you have.