In a scenario where I have an interviewee in front of me I would base my judgment off of their reactions and comments. If they were fired or let go I would ask them what happened and why it happened. If they give mature non-angry responses and outline their mistakes and how they learned from it, then it would be a good response. I would ask them if they thought it was their bosses fault the company, or was it their fault. I would ask what sort of life and business lessons they had learned from their previous employment and how they were going to implement said lessons in this new job opportunity.
If I was being interviewed as a potential employee I would like to not necessarily bring up mistakes but to discuss how I could have made different choice for better outcomes. If I can give a reasonable response to tough questions as well as be honest I think a potential employer will have an easier time trusting you. People who try to hide and cover their mistakes haven’t learned from them in most cases. You cannot become better without mistakes because it creates that life lesson that molds you into something better. The mistake I had made previously was being late to work a few times in a month. I was not managing my time and schedule right so I ended up staying up late numerous times that then put me behind in the mornings. I was verbally counseled and written up on paper. I realized the way I was managing time was not conducive to a good work environment and it looked bad on me to show up late. Even though I loved my job and took great care, being late automatically made me look like I don’t care. I made changes to my lifestyle and scheduling to the point where I was never late again for that job. I learned my lesson and it has served me very well since.