I will refer, again, to LaTeeDa's quote in my signature:
Unacceptable behavior is unacceptable.
I can understand people's reasons for lying, be they medical or situational.
Still doesn't make a difference.
I'm not completely hardcore on shutting out someone for lying, though.
My youngest child lies about her father all the time, because she feels she needs to defend him against me. I understand that. I don't condone it, but I also don't confront it, because I know that she's lying and she knows that she's lying and I know that it's what she needs to do right now, and when she's ready, she will stop.
I know my AXH lies every time he opens his mouth. But there's no reason for me to confront him. He has created his own reality and he's drinking to maintain it and he's lying about the drinking but the rest of it? He really believes. He lives in a fantasyland of his own creation where he's the guy with the white hat and drinking is OK. I think I left partly because I knew he'd never move out of that fantasyland.