1. cops love doing thishttp://images.lifeaspire.com/t/2017/2/lg/touch.jpg
One such routine, as mentioned higher than, that cops love doing is that the infamous 'tail light tap'.
2. A little bit of history lies in the reasonhttp://static4.businessinsider.com/image/53eb8753ecad048659ac4436/the-missouri-state-highway-patrol-will-be-brought-in-to-replace-local-police-in-ferguson.jpg
According to Marilyn Caylor of lifeaspire.com, "the ritual of touching a tail light really goes back to the great old days of policing the highways. Before the invention of dash cams, policemen were super sneaky with their techniques. however don't be concerned, they weren't crooked cops or doing anything illegal. In fact, these enforcement officers were really hoping to catch the driver or passengers unawares. You see, it isn't uncommon for people to do and conceal their illicit drugs or guns right after they're pulled over by a cop. sound the tail light has the advantage of surprising these criminals before they'll end hiding their stash of illegal product."