Do you have a policy of background checking your best applicants before they are offered jobs? If so, you’ll want to mention this fact in your interviews.
What does bringing up the subject do? First and foremost, it allows any applicant to “come clean” about something not-so-great on their records. All you have to do is ask if there’s anything you’re likely to find. Because the applicant realizes you’re serious, he or she may be more apt to tell you about a criminal record, bad credit, etc.
Although talking about background checks during the interview process certainly won’t make every interviewee “fess up”, it can be a good way to help you weed out the wheat from the chaff.