Please correct me if I'm wrong but I don't recall if Smith was ever charged/convicted for any of his domestic violence instances. If he wasn't ever charged, those things wouldn't show up on a background check.
The only thing I'm aware of (and it wouldn't have shown up on a background check, because it just happened) is Courtney filed a five-year domestic violence protection order against Zach late last month and the judge granted it. It makes it illegal for him to come within 500 feet of her for the next five years.Gotcha. Yup, nothing would show up on a background check then.
I don't know the process and burden of proof necessary for getting one of those, however, I think it's a fairly damning piece to the puzzle because I imagine they don't just hand them out on a whim.