I believe I have mentioned Justin McShane before. A very interesting and knowledgeable PA DUI attorney. He just released another article about the presumption of innocence in DUI cases.
To summarize, it appears that the innocence of the person sitting in the back of the squad car, or in the defendant’s seat stops being questioned, and we find ourselves asking “I wonder what he/she did” as opposed to “I wonder if he/she did anything wrong.”
If you have the time, I suggest checking it out.