Well, interviewing a bunch of specialists saying "this contradicts all I know about medical diagnostics for this and this reason" - like we see happening here -

Well, interviewing a bunch of specialists saying "this contradicts all I know about medical diagnostics for this and this reason" - like we see happening here - and then asking the Theranos reps "could you please explain what these experts are missing here, in detail" would be a good start. Of course, Theranos could bullshit their way out of it, but distinguishing bullshit answers from substantial answers is usually much easier and more accessible to non-specialists than figuring out if the whole thing is bullshit from zero.