Nice comment by frusty. There is no simple answer to your question --- everybody lies occasionally, and for various reasons ; some people lie a lot, and even when there is no apparent benefit to them. They may be helpable by psychoherapy / skilled counselling --- but of course only if THEY recognize that this is a real problem for them and sincerely apply themselves to changing. And there's the snag --- they may cause problems to others, but probably also lie to themselves, and don't want to recognize the problem