I'M a birther-but how can she know he can't?!
To the extent that we can know anything, it seems reasonable to deduce that the sun will come up tomorrow and that, if BHO could have proven his American citizenship by now, using valid documents, he would have done so instead of paying millions to hide them.
In addition, she has covered many of the court cases and the research they produced. The cases were not advanced because of standing.