I wonder, are they trained to look for that in formal police training? Or are they taught that by private consultants?
This has happened to me personally about 5 times in my life where they stop me and get specifically frustrated that I did nothing wrong and make something up once I ask them. The one and only time it got really bad was when a cop was following me for 2+ miles and finally stopped me took my information and threw it as hard as he could at me when he was done with it with a really bad attitude.