i need to understand how a person becomes a compulsive liar?

No.

The best you can do is be aware that any chance they get to make up a story or tell a lie for no reason at all, they are going to choose to lie.

One thing about a compulsive liar, is they are really good at keeping secrets. They don't gossip. They need a lot of friends to

keep bouncing from one to the next with the latest drama.

They love to meet new people so they can really tell lies. Where they can be anything at all and that person will never reach any of the people that know them.

My friend is compulsive and I can tell him a story of something interesting that just happened to me, and another person will walk up and he will tell them the story I just told and include himself in it like he was with me and I am standing right there .

He has to know I know he is lying, since I gave him the story a few minutes before, but he doesn't seem to be bothered by that.

I always consider anything he says no matter how small is a lie and that keeps me from being a victim.

Probably not, because compulsive behavior is hard to deal with. The best you can do is to protect yourself from such people.

Compulsive liars are often sociopaths, who can be recognized by their poor impulse control, drug and alcohol use, scorn for the law, recklessness, stealing, frequent loss of employment and frequent change of residence, and very poor empathy for people. Avoid such people! They're often charming but the charm is a tool which they use to dazzle people while they're using your credit card.

This will probally help a little bit.

http://en.wikipedia.org/wiki/Mythomania