speeding citation using stopwacth

I recived a speeding ticket in a small town in Pa. I agree with the cop that I was speeding about 5 or 6 miles over the speed limit.
He told me he clock me at 51 in a 35, which I didn't agree with him. I asked if he clock me on radar and he told me on a robic stopwacth. I plead not guilty and have a trail date. What is a robic stopwacth and what are my chances of getting out of it.

[racer72]

All the officer did was time you between 2 points set a specific distance apart. Based on the time it takes to travel between the 2 points determines your speed. It is a very accurate method for determing the speed of vehicles and almost indefensable. Good luck.