Cops in NY and some other states don't even need radar. They go to training classes and then can perform what'* called a speed estimation.
They can literally stop you based on their observation of your speed, and their "training" and give you a ticket solely based on their "guesstimate".
And yes, it holds up in court.
I have friends that have gotten in big trouble, and paid huge fines based on what supposedly was a speed estimation, with no radar unit to back it up.
How you like them apples?
And nowhere in NY law anyway, are they required to show you the radar. I asked nicely, and was told I didn't have any right to see it. Almost landed me a reckless driving charge.
And yeah, I live in a one traffic light town, that has part time officers, but has a Hemi Charger, an Expedition, 2 9C1s, and a K9 unit. Oh, and they just installed plate reading and capturing software/hardware on all the units.
NY is one of the most police happy states I've ever seen. Even in the middle of nowhere.
So, your laws may (and probably do) vary.