Wait, there is no evidence other than a cop estimating your speed as you drove along? I mean, did they actually measure your traveling speed with some cop-gadget-speedy-measuring-device or have any video footage? If so, you can always question whether their measuring device was calibrated correctly, in which case they have to prove it to you (at least thats what its like here). I did that a couple of times and got away with it twice, one time their protocol wasnt complete, another time their speeding-gun-thing wasn´t calibrated at all.