#1 – Here’s a little history
According to Marilyn Caylor of lifeaspire.com, “the ritual of touching a tail light actually goes back to the good old days of policing the highways. Before the invention of dash cams, policemen were super sneaky with their tactics. But don’t worry, they weren’t crooked cops or doing anything illegal. In fact, these law enforcement officers were actually hoping to catch the driver or passengers unawares. You see, it’s not uncommon for people to try and hide their illicit drugs or guns right after they are pulled over by a cop. Tapping the tail light has the benefit of startling these criminals before they can finish hiding their stash of ill-gotten goods.”
#2 – There is another reason to think about
The light not only is a way to startle any criminals potentially in the process of hiding their illegal activity, it could serve another purpose. Should the criminal decide to harm the cop, drive off, or both without the cop registering their information, his fingerprint will be on the rear light to identify the vehicle.
#3 – With cameras, this practice is not an essential one
At least not in terms of catching a vehicle that has escaped. The tail-light tap is a practice that is less and less prevalent because cameras capture not only a license plate in most cases, but potential sketchy behavior by the driver as well. Those who still light-tap are probably just doing it out of habit.