Experienced trial lawyers say a bench trial is just a slow and expensive guilty plea.
I have seen one pro se defendant in a traffic case (reckless driving, speeding, improper lane change) get an acquittal, but this was a jury trial. And he had two cops take the stand against him: the one he supposedly almost sideswiped, and the second one who came along later and took reports from both parties, because supposedly he made some kind of "admission" to the investigating cop.
He argued to the jury (himself-- no lawyer!) that he wasn't at fault and never said otherwise to anybody, and naturally the second cop will back up the first cop's version of events, and that first cop was too embarassed to admit he was the one who almost caused the accident (there was no accident, just a near-miss). And the jury found that this one single citizen's testimony was enough to cast reasonable doubt on the cops' stories.
P.S. Don't count on this happening again anytime soon. But I was there and saw it happen in court that day.