I don't think trying to select for an ethical core really works. Ultimately, you are either going to go along with the people around you or you are going to stick to some principles that aren't shared by everybody, and in the latter case, you're going to be unsuitable for the job, because you're not running the company.

So looking for evidence of ethics in an interview is just looking for a smooth talking hypocrite, even if you think you really want to.