Under what circumstances, if any, would you lie?

I look at this like violence... non-violence is the ultimate goal, yet I know that I would not be calm and preaching non-violence to someone trying to hurt me or someone else. I would be stopping them by any means I had to use. This is unstable ground if you step back and look at language objectively and what it means to lie. Bottom line, It really comes down to intentions I think.