I've nailed my brother a few times on it and he was told "loud and clear" that I knew his lies were deliberate and that he knew they were deliberate.
How right you are. At times I have felt the manic-depressives I have known should be called manipulative-depressives instead.
You may have personal experience with people who use depression as an excuse but it is not accurate to flatly state that all such individuals do this. I have personal experience with quite a few diagnosed clinically depressed people who do everything in their power to shield others from their pain. They NEVER use their disease as a crutch.