The inability to be able to separate the truth from lies. To justify their behavior. I am sure you can add to this partial list. The hardest one to catch is the occasional liar. They are the most dangerous.
Liars pick their targets.
There are some people who are incapable of ever telling the truth. They live an entire life in a cloud of lies. Their whole life is a lie and their entire experience is a set of lies. Lies are not an occasional ocurance but a way of life. Every time they open their mouth they lie.