Are you positive that when you first left work you weren't speeding? I know alot of people drive a little faster then they think they do...
A police officer does NOT have to show you the radar gun, but most police cars when they turn there lights on, it turns on the camera...if he didn't turn his lights on until yo were stopped getting ready to turn in.
Then you could probobly get out of it...but the thing is if you get out it and make this cop look like a douche, then he's gonna remember your face, and next time he'll find a small driving mistake and pile on all he can