Something Might Pop out of the Trunk
Believe it or not, another mind-blowing reason why cops tap the tail light of your car when they pull you over is that they suspect something or someone might be hiding in your trunk. I bet the cops would freak out if a ghost or a scary clown pop out of your car trunk in the middle of the night.
Source: Youtube
If the driver is a criminal and he has an accomplice hiding in the trunk, cops automatically leave their fingerprints on the tail light while making sure that the trunk is shut. This strategic plan keeps the police safe from being killed and helps them identify cars that are driven by criminals.