My brother was a cop for 25 years. He said the only time that the radar gun accuracy was beaten in court was when the defendant asked of the cop the question "How was the radar gun calibrated?", to which the cop replied "With a tuning fork" (which is how they all are calibrated), and the defendant followed up with "How was the tuning fork calibrated?", for which there was no answer, ergo, reasonable doubt. I have read recently about how the radar gun manufacturers have amendened the calibration process, but it might be worth a try.