Lies....

"A single lie destroys a whole reputation for integrity" ~ Bathasar Gracian

OK, lets talk lies..... I have a real issue with lies, they erode the very foundation of any relationship.  Hubby has been sneaking cigarettes, ok, not that bad a thing, but he keeps lying. When I ask blatantly, 'did you buy cigarettes' and he says no....its a lie. All these little lies add up to a lot of mistrust. He doesnt quite understand. Now dont get me wrong, its not all about cigarettes, we do have a history or issues with lie, but I thought we were over it, turns out, we aren't. I come from a family of liars, its the one thing that is a deal breaker for me. My alcoholic father used to promise us the world. It took us a long time and many heartbroken moments to realise that we cant believe a word out of his mouth, I didnt want to spend my adult years the same. But here I am at nearly 28, going through it with D. D has bi-polar, and a fucked up childhood, and yes it helps to justify in his head the lies, but we need to find a way out of this.  I do need to do more research on bi-polar, because the two are linked, but where do I draw the line between just an excuse and a real reason? How do I know that if it is part of the bipolar, that I am emotionally capable of dealing with it?  How do I trust him? How do I trust him not to go looking for something elsewhere?