I see your argument, but i wouldnt bring up in court you got a radar detector. I would mention the traffic and stuff though. your argument says his speedometer could be off, his could say yours is off, which might require testing of your cars, if thats teh case it could cost you more money in the long run. Although im not sure what the speed limit is where you were at. if it was 75 or something and you were going 80 then yeah i would fight it. Most judges will throw it out of court if its under 15mph over since they could have just tagged you trying to pass someone. But its up to you.

Also the officer may not even show up to court so you may just get off by that.