The certificate shouldn't matter in the interview itself - it is just a way to pair down the choices of who you interview when you have many candidates. If you have knowledgeable people in the interview process (i.e. at least have a dev present for a dev interview, not just managers or HR people) then you should be able to catch those that don't really have the skills.
Heck, even people who genuinely have a certificate might be rubbish overall but revised well for the exam days - you'll hopefully weed those out in a good interview process too.