I was given a speeding ticket today. I saw CHP on the side of the road with his gun and immediately looked at my speedometer. It read about 75 in a 65 on the highway. When he pulled me over he told me his gun said I was driving 82. But on the ticket he wrote as my approximate speed as 75+ but wrote where it says "Beat" as 82. I don't know what that means. But I know that I was not driving at 82 MPH. He also said that he gave me a break writing down 75 instead of 82 so I can go to traffic school.
California state law states that the radar device used must meet or exceed the minimal requirements set forth by the National Traffic Highway Safety Administration. The radar gun used must have been calibrated at least three years prior to the alleged violation by a certified and independent radar calibration facility.
It is also normal practice for the officer to calibrate his radar gun before and after a citation. If you want to know how that is done google radar and tuning fork.