I don't know that you have any defense besides hoping for dumb luck at court. If you can save a point on your license by attending traffic school, that might be the best option to consider. If you have already done this, and you need this job for your livelihood, you may want to follow the previous suggestion and obtain the advice of a local attorney that specializes in local traffic matters. There may be some peculiarity in SF County with regards to dealing with traffic matters that are uncommon or even unheard of in other parts of the state. SF is the only county in the state that is both a city AND a county, and its governmental makeup and actions seem to often defy typical legal conventions.