answering "have you ever been fired?" in an interview

A reader writes:

I was in a job interview the other day and everything was going well, until I was asked if I had ever been fired, and if so what were the reasons. Having never been asked that question before, my initial reaction was to feel that my privacy was being invaded and that this was an inappropriate question. Additionally, I was asked to sign a statement that I had not answered this question honestly, or it would be used as a reason for dismissal.

Since that interview, I have learned that this is a common question. The idea behind that question is that whatever happened before will happen again. (This was also said in the interview and not "may," but "will.")

I was indeed fired from a job about 10 years ago. I did the job well, I contributed to the organization, but my relationship with my supervisor was not good (this really can happen). Since then I ensure that I do both -- I do the job well and work at my working relationships.

So my question is, how can I answer this question honestly? Is it a trick question?

It's not a trick question. It's exactly what it seems to be -- a genuine desire to know if you have ever been fired before and, if so, why. If you put yourself in the employer's shoes, you'll probably understand why an interviewer would want to know this. It's not that no one who has been fired could ever be the right fit at a different job -- but it certainly does provide useful information about problems that the candidate has run into in the past (even if only personality conflicts). And perhaps most importantly, there's a lot to be gleaned from the way the candidate discusses it now. Do they just seem bitter and angry about it? Have they learned from the experience? How has it changed how they conduct business? And so forth.

It's hard to tell you how you yourself should answer this question without knowing more specifics, but one option might be talking about how you ended up in that situation, what you learned from it, and what you do differently now as a result.