A TikToker has recently explained exactly why police officers touch the back of the car they've pulled over.

Now, if you've ever been pulled over here in the U.S, you may have noticed the officer usually taps the rear of your car before approaching the side and getting you to roll your window down.

The clip posted by TikTok user @mr.alexaa shows a series of cops touching the back of a vehicle, usually on the boot, before heading towards the driver-side door.

But why do they do this?

Apparently, it's all part of the standard policing procedure and was put in place to help protect both the people in the car and the police officer from potential harm.

According to the majority of people in the comments sections, it's so the officer's fingerprints are on the car in case anything goes wrong during the stop.

Traffic safety expert Trooper Steve Montiero has backed up this theory, explaining that it's an essential part of policing.

Speaking to News 6, he said there are 2 reasons behind it...

He said: "When law enforcement officers conduct a traffic stop, there are plenty of procedures that need to be done, not only for the safety of the violator but for the safety of that officer. One of those things is proving that that officer was with that car, so when officers approach a vehicle, they touch the rear of it."

He went on: "The first reason is to make sure that the trunk is closed. It may sound a little crazy, but you want to make sure that no one is about to jump out of the trunk and that it's properly secured.

"Touching the rear of the vehicle puts the officer's fingerprints on that car, showing that he or she was there with it. In case the driver decided to flee the scene, or if something happened to that officer, it ties both the vehicle and the officer together."

He added: "This is just one of the many things that take place during traffic stops to ensure everyone's safety."

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Since the video was posted, it has been watched over twenty-nine million times, with thousands hitting the comments to share their thoughts on it.

One user said: "I am a law enforcement student in Arizona, and we were taught to do that not only for the fingerprint but to make sure the back is closed."

Another echoed: "We also do it to make sure the trunk is closed, so no one pops out to shoot us. At least that's what I was taught at the academy over twenty years ago."

"The reason cops touch our taillights is to leave their fingerprints so they have some proof in case something happens," a third commented.