I just remembered a personal story that happened more than 15 years ago.
When I was a bochur, I had a practice I often did whenever I would walk 13th Avenue in Boro Park. I always had some quarters with me, and whenever I would spot a meter maid, I would walk in front of them and put quarters into empty meters. (Yes, the bochurim in those days!) More than once, I drew their ire, but there was not much they could do.
Once, I saw an empty meter and proceeded to put in a quarter as the meter maid was approaching. The cop got really upset, and she proceeded to scan the registration and give a ticket. I waited until the cop left and checked the ticket, and saw that the cop wrote "Put in money after car was scanned" - a blatant falsehood. (Legally, you are not allowed to feed a meter, and you are obligated to move your car after the 2-hour allotment, so the cop could've given a ticket anyways for that. But this cop decided to lie instead.)
I pulled out a notepad from my pocket and left a note: "I am a witness that there was money in the meter when the officer scanned the car." I also wrote my name and phone number, and slipped the note in alongside the ticket.
Weeks later, I got a phone call. "I brought your note to court and the judge dismissed the ticket," the caller said. Who was the caller? Pinny Ringel, then a co-owner of Hi-Tech 2000, and now a (seemingly losing) candidate for Boro Park District Leader.