You believe way too much in the system. They DGAF about the DV. Maybe the charge will stick, maybe it won't. Sure they like it more than a traffic ticket but it's not much more valuable to them than a DUI. People get smacked upside the head every day and it's no big deal in their world. They want to use the DV as the pretext for a fishing expedition, In their minds maybe they can nail the guy on drug dealing or whatever other more interesting and valuable crime they can find
In the particular case I described above there were some factors about who the person was that make me pretty confident the police were wanting to sniff around for something juicier (though because of his situation, even the accusation of domestic violence was going to be enough to ruin certain things for him, even if nothing ever came of it). That's SOP for many things where, for example, certain departments train officers to use traffic stops as pretexts to "elevate" the encounter to a felony arrest. They don't care that the guy failed to come to a complete stop at that stop sign, but they like their chances of getting consent to search his vehicle and finding (or, in the egregious cases, planting) something else.
Edit: I see that you weren't replying directly to me. Sorry about that.
