Earlier quoted context omitted.
How do you interview someone more experienced than yourself? In the last set of interviews I had to do, I've ended up doing the role of talking to people about the technologies listed on their CV and asking them detailed questions to find out just how well they really know them. This just because I happened to be the person in our company who knew a little bit about most of the things that the people we were intervie…
The alternative is for our field to have a strong organization that vets it's members, like any other professional field such as lawyers and other engineering disciplines. That way, before you even meet the person, you can assume a level of competence and can get into much deeper questions faster.
If you ask both candidates a question like "Johnny climbed up to the top of the hill, where was Johnny when he stopped climbing?" and then get a blank stare from both candidates then you are going to conclude that you can't find any 'qualified' candidates because they can't answer a dead-simple question.
The vetting of candidates used to be contributions to software product releases and publications (in addition to degrees and GPA). A motivated hiring manager could also search mail archives of popular open-source projects.