How thoroughly do you check references?
This video talks about the threat of a reference check, a technique adopted by Dr. Geoffrey Smart who wrote a book called Topgrading. The threat is more powerful than the check itself. If you aren’t quite sure the candidate is being truthful in the interview, tell them that you are calling a recent manager of theirs later on today to ask him what the biggest problem he has had with the applicant is. In reality, the old manager probably wouldn’t say much at all but this is a great test to see what candidates will say.
It is also useful to ask the candidate to give their reference permission to answer more specific questions, instead of just giving a start and end date of the job. You can ask the reference about things you have had doubts about in the interview. Remember, general questions will give you general answers so be specific.