Renee, ten years ago it was a bit different. The metro cops were a bit "gruff". I dont know what happened, but its like they all got sent to sensitivity training classes. I have seen them stop a group of 5 tourists who didnt validate their tickets, make each pay the 12.000 and stil have them saying thankyou and laughing when they parted.
I do my part to help out the tourists when I ride the older trams (47, 48, 49, 2, 23, 2B). I sit by the validation machine and when I see people sticking tickets in, and pulling them out and sticking them back in, each time expecting something to happen. But the old tram machines arent electric, they are mechancial. I take their ticket and validate if for them. I was a hero for a group of spanish a few weeks back. You would think I hung the moon.
If when approaching an inspector (when there are inspectors .... not terribly often), the inspector looks me in the eyes, I will reach in my pocket for my wallet. Most of the time they will say jo napot before I get it out and wave me trough. A few times I have gotten it all the way out and begun to hold it where they can see my residency card, but no one has ever actually looked at it. They just wave me trough. I used to point to my head (old and balding) but one inspector stopped me to tell me bald guys had to pay too .... then laughed and waved me on.