Uncertain officer

A couple of weeks ago a was coming back home with my wife from picking up my son from daycare. I was on the freeway when I saw red flashing in the car and after a quick pick in the rear mirror I discovered there was a police cruiser pulling me over. I immediately checked my speed because I assumed the most probable reason for him to stop me was speed. The speedometer signed 70MpH. The speed limit on that stretch of road is 65MpH. I pulled over and the officer told me he stopped me because I was doing 80MpH. I drive a Saturn SL. I'm sure it can do 80 if the wind is favorable and there is a stretch of road long enough... you know what I mean? He took my license, went back to his car and came back with a ticket. He said he wrote 75MpH on the ticket because he had to calibrate his equipment. Then he suggested to have my speedometer checked. So I did. I went to the dealer and got a document from them that said the speedometer in my car is working following factory specifications. According to Wikipedia (http://en.wikipedia.org/wiki/Speedometer) that mean an accuracy of 10%. At 70 miles an hour it means that I could have potentially drive at 63MpH or up to 77MpH. The ticket the officer gave me has the Radar/Lidar Unit/Patrol Vehicle No. blank. If you want to give somebody a ticket within the speedometer margin of error you better have your instrument nicely calibrated. The fact the he said I was doing 80 and then he wrote 75 on the ticket doesn't make him sound very certain. Was I speeding or he thought I was speeding because I had no reason to drive fast. My wife and son where in the car, it was the end of the day and the most urgent thing to do was to put the baby to sleep. So, what should I do? Should I go to court ( I live in California ) and explain this to the the judge? I was reading some of the other posts in this forum and it seems it's the general consensus that in case of my word against the officer one the judge it's going to take his side. Would he/she even bother to listed to all this technical explanations about speedometer margin of error and inaccuracy from the officer part? I have no problem to pay if I made a mistake, but it seems to me the officer was bored or he need to make few more bucks. I can already see the first reply to this thread to be: “ You said you where doing 70Mph, you should just pay the ticket”. But was I doing 70 as my car said, or it was actually 65Mph? That is 7% difference way with the tolerance of the instrument. The point is: If somebody accuse someone to have done something wrong it should be really certain and it should be able to prove it. Whit out this what would prevent officers to came our with stories to con people out of their money like it happen in other counties?