Cops Often Touch Car Tail Lights During Stops, And There’s An Important Explanation

For most of us, getting pulled over by the police is the most likely way we’ll come into contact with them. After all, in any given year officers pull over millions of people. And for the police, this is a fraught and danger-filled moment. Who knows what the person they pull over will make of it? Who knows whether they’re armed and dangerous or if they come in peace?

It’s not just physical danger that the police face: there’s also the risk of getting things wrong. Traffic stops are covered by the Fourth Amendment of the U.S. Constitution. This protects citizens against “unreasonable searches and seizures,” forbidding either without probable cause. When you’re stopped by the police, it counts as a seizure.

What does “seizure” mean here? After all, the cops don’t have to take you away or anything like that. Well, roughly speaking, a seizure occurs when the circumstances you’re in make it clear to you that you’re not free to just leave. The police officer must demonstrate that this is the case and must show authority. If an officer doesn’t stop you by the book, you might have a “Bivens case,” the name for a legal precedent countering illegal seizures that can result in damages against the police.

The police can stop you if they have “probable cause.” They don’t need to suspect that you’re doing something criminal, though. If while you’re stopped, they come across something that leads them to think you are involved in something criminal, they can then do what’s called a Terry stop. This is a bit more involved.

Basically, a Terry stop is a nickname for being stopped and being frisked. The name comes from the case Terry vs. Ohio that was heard in the Supreme Court. It decided that a cop checking you for weapons is not carrying out an illegal search. He or she does not even have to believe you are committing — or have just committed — a crime.

Sometimes state laws will allow the police to stop you without the Fourth Amendment being involved. And sometimes a state will even permit stops by other officials of the government if they think you’re up to no good. Still, this is an area where the police don’t do things lightly, because they know there can be legal consequences if they don’t take care.

But regardless of which state you’re in, the cops can’t pull you over for no reason. One big cause for stopping you might be your behavior. If you’re weaving all over the road or driving way too slowly, the police might suspect that you’re under the influence. If you seem to speed up when you catch sight of them, they might suspect that you’re up to no good

Another reason that you might be stopped is that your car looks like one that has been used in connection with a crime. And it’s not just your car. You might find yourself pulled over if you or anyone else in the car with you looks like someone for whom the cops are looking.

Of course, a common reason to be pulled over is that you just broke a law. That might be that you went faster than the speed limit, or ran a red light, or didn’t halt at a “Stop” sign. Or something could be wrong with your car. Maybe one of your brake lights is out, or your car’s registration is not up to date?

So how does it work? The following description is based on the testimony of a real-life cop working in Portland, Oregon, and related via website Portland.gov. The first thing he does is figure out where it’s safe to stop. He doesn’t just turn his lights on when he first spots you. He’ll follow you until there’s a space where he feels you can safely pull over.

The cop will contact his dispatcher to let them know what is going on. He lets them know where he is and the tag of the car he’s stopping. Then he sets his lights to flashing and fires off a whoop of his airhorn. So the driver now knows that they’re being pulled over. Hopefully, they choose the spot the police officer had in mind, but of course they don’t always.

The cop turns on his floodlights and his spotlight. The point of the lights is that they help mask the police officer from the driver. So if the latter is planning something nefarious, they’ll find it hard to pinpoint the officer. He parks behind the stopped car, lets dispatch know that he’s come to a halt, and then heads for the other vehicle.

The police officer is now in a scary space. Not only is he worried about the driver he’s about to accost, but he’s vulnerable to passing traffic. As he reaches the stopped car, he gives a quick tug on the trunk lid. The idea is to make sure no one jumps out of it behind him. For a similar reason, he checks the back seat. He wants to know for sure the number of people involved here.

The officer will then stop by the driver’s window, set back a bit. He’s hoping to see that the driver has lowered his window and put both hands on the wheel. If he has to make the person roll down the window, who knows what will confront him? Now he introduces himself, explains why he’s stopped the driver, and asks for their license and insurance.

Now one thing you might have noticed as the cop came up to your car was that he tapped quickly on your tail light. Seems weird, right? But this is very run-of-the-mill, so common that some cops do it without even thinking about it. Why on Earth, though, would a policeman do such a thing?

Well, it’s actually a pretty old-school tactic, according to experts. Back in the day, before the invention of things like bodycams, there was only one way that police could prove they’d stopped you. And even today, they still do it. Driving law expert Joe Hoelscher explained to Reader’s Digest in 2021, “It is less important now that video is ubiquitous, but it requires so little effort that officers are still trained to do it.”

Bodycams are not as universal as we might imagine. Apparently, in 2016, fewer than half of all police forces used them. Even among those that did, not all of them required cops to turn their cameras on when they made a traffic stop. And in the same year, only slightly more than two-thirds of police cruisers had dashcams.

Dashcams can provide vital protection for police. For instance, in August 2021, a routine traffic stop in Aurora, Illinois, went very wrong. A cop reportedly pulled over a car for ignoring a “Stop” sign. But what started out as a minor traffic violation turned out to be a much bigger deal. Dashcam footage appeared to show the car's three occupants getting out and attacking the cop, choking him. The trio ended up facing attempted murder charges.

A dashcam isn’t just good for providing evidence of incidents: it can help prevent them in the first place. Police1.com noted one study found that police said they could defuse a bad situation by telling drivers that they were filming the encounter, while more than half of drivers agreed that their behavior changed if they were being filmed.

But the biggest advantage of a dashcam is that it provides objective footage of what went down. Now it’s no longer your word against a cop’s. And the same study showed something else very interesting: police tended to be cleared over any complaints from stopped drivers on nearly every occasion that dashcam footage was available. Half the time, defendants simply withdrew complaints when they knew a camera had recorded the proceedings. So, why might a cop still touch your taillight?

The answer is simple: fingerprints. Hoelscher says, “Leaving a thumbprint on the brake light is an old-school way to tag a car with a fingerprint, so it can be identified conclusively as the vehicle involved in a stop should the officer become incapacitated.”

Some people believe that the police do it to startle someone who is drunk or who might have something to hide, as a means of shock or intimidation. Hoelscher refuted this, saying, “Officers should do it subtly, so the driver doesn’t realize it’s there. Otherwise, a perpetrator could remove the print.”

There’s another side to the cop doing this: if your tail light is dirty, the fingerprint may be very visible, and your next stop might go badly because the officer will know you’ve been pulled over recently. So Hoelscher has some wise counsel for drivers. He said, “My advice is to wash your car after getting a ticket or the next time you get stopped.”

As far as court goes, camera evidence is admissible — and sometimes it can be invaluable. A jury often values dashcam video because it allows them to see what happened without relying on someone’s memory. Likewise, Police1.com noted studies had found that most prosecutors tended to welcome dashcam evidence and found it useful when a case came to trial.

If a case does go to court, it will usually be in the cop’s plus column if he or she had reasonable suspicion when they stopped you. Still, they don’t actually have to tell you why they pulled you over. Website Autoinsuranceez.com advises that for your part, it’s best not to inflame things. Keep your hands on the wheel, don’t fidget, and don’t reach for something suddenly.

Things don’t have to end badly, though. As per Autoinsuranceez.com, half the time there’s no negative action toward the driver — at worst a warning. Otherwise, the driver usually just gets a ticket. Only in a few cases does the incident become something more serious. Slightly fewer than four in every 100 stops turn into an arrest or a search.

And cops can keep the risks in perspective, too. As per a study titled Policing, Danger Narratives, and Routine Traffic Stops cited in journal the Michigan Law Review, on average in the U.S. an officer is killed once per 6.5 million stops. Even assaults that end up in serious injury are somewhat rare, happening only every 360,000 stops. Yet one in every 7,000 stopped drivers does attack a police officer, though — so you can understand why they’re always wary.

One thing the Portland cop pointed out is that dispatchers start a timer when the officer first reports a stop. When the timer runs out, the dispatcher asks the officer if everything is okay. In the absence of a positive response, the next step is to send the nearest couple of cruisers to race to the officer’s aid.

One Florida cop told the Reader’s Digest that one thing that bothered him was that drivers were scared of the police. He recounted that a woman he’d pulled over had made sure to stop where there were lights. She’d told him she had been frightened of what he’d do. He said that he’d thought, “Wow, we’re the bad guys now.” Truth is, of course, they’re just people doing a job, so if you hear a tap-tap on your tail light here’s some free advice: license and insurance out, window down, and try not to make a scary moment for you both even worse.