Doesn't the officer have to pace you for a certain distance before pulling you over for speeding? He pretty much caught up and then pulled me over. After he caught up I slowed to the speed limit while he turned his lights on.
There is no specific distance required for apace under CA law. In fact, if the officer is radar certified or can convince the court that he possess the requisite training and experience, he can make the case based upon visual estimation of your speed alone.
And, logically, if he has paced the vehicle you passed and it was doing at or above the speed limit, then you clearly exceeded THAT speed.