Your question already shows that you have the proper analysis ["as close as /practicable"]. When I have seen this argued (usually in the context of a DUI stop) the argument tends to focus on safety and awareness. If there was no one there and if you made the turn safely and reasonably then isn't that as close as NOT possible but practicable. The counter argument is usually the officer saying something to the effect, if the driver really was aware of what was going on, he would have seen me! Or, my attention was drawn when another car stopped short, surprised by the "sudden movement" of the offending driver. It all depends upon the traffic judge and the police officer. Find a way to win your argument without forcing the judge to denigrate the officer. ... Good luck.
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