Policing in America brings with it some additional challenges that may not be as pronounced in other states. It is precisely for this reason that local police officers have to perform “special actions. For example, they lightly touch the taillights on the car they stop.
Firearms are legal in the U.S., so police work carries some dangers. Because of that, police officers have certain regulations about it, for example, when they stop a car they must touch the taillight of the stopped car with the palm of their hand. This is not a tradition, but a reasonable requirement. It arose at a time when police officers did not have video recorders, and there were not many cameras installed on the streets and roads.
The point of such actions is very simple – police officers leave their own fingerprints on the car they stop. They do not necessarily touch the brake lights specifically, any part of the body can be touched. However, most of the police officers touch the surface of the taillight or the lid of the luggage compartment.
The fingerprints, they leave for their colleagues and for court proceedings if anything happens to the police officer. For example, if he is taken hostage or physically harmed. With this simple action, it will be easy to prove in court that the police officer braked that particular vehicle.
Nowadays, the technique has been removed from the U.S. police statute, as it is not necessary. Nevertheless, it has become a tradition, and police officers still leave their fingerprints on all vehicles they stop.