I know there's a lot of legal mumbo jumbo about jammers but have you ever watched any of the test videos on youtube? It's blatantly obvious to the police officer who is beaming highway traffic. There is a video where the tester is hitting every car and then the test car comes along and he can't get a read on it at all. He then shoots cars next to it and all around getting readings instantaneously. When he tries to hit the test car again, no read. I guess you can say "it works" but I think being blatantly obvious might get you pulled over anyway. Hmmm but I guess legally, if it's not illegal in your state, and the copper doesn't get an accurate read, then there's nothing wrong with it? And then you have cops who are certified to visually measure speed. And pacing.
Here's the vid: