It's impossible to know.
Unfortunately.
Remember Ellen DeGeneres?
A funny, friendly, and nice presenter who even hosted the Oscars twice. But if it weren't for the testimonies and actions of former colleagues, as well as videos of her being rude to her celebrity guests, we would never have known about it. Ellen doesn't allow her colleagues to look her in the eye, speak to her, or eat meat in her presence. On camera, she was extremely rude to Mariah Carey. He even went so far as to offer the singer a drink to put aside the assumptions that she was pregnant (she was, and that was a private matter until then).
Narcissistic liars are everywhere.
But that's a famous person, so I'll tell you another story. About ordinary people.
I knew a man who was such a good liar that many people in his inner circle had no idea what a monster he was. Others, however, only had a vague impression of his true character.
His secret: he believed his own lies.
Even if he, in the deepest and most secret dark chamber of his mind or in what remains of his heart, knows what he truly is, he simply buries the lies so deeply beneath the dirt that he is able to change his truths and believe his lies.
This man drove people to depression, fired others simply because he could, destroyed the careers of other colleagues out of pure jealousy, and tried to bribe people on many occasions for his own benefit.
And yet, I saw him cry - literally CRY, with tears and everything - after someone accused him of some of his mistakes.
The effect of this?
The honest man – the accuser – was considered a horrible person, while the pathological liar was believed to have been falsely accused and was therefore innocent.
A victim.
Pathological liars usually have a way of believing their own lies, because otherwise, they have to admit to themselves that they are monsters.
Another celebrity story. Remember this guy?
Lance Armstrong
He was a former American professional cyclist, the 1993 road cycling champion. He became famous for winning the Tour de France seven times consecutively—an absolute record in that race—between 1999 and 2005. However, in 2012, a few years after ending his sporting career, he lost all titles obtained after 1998 and was banned from competitive cycling by the International Cycling Union due to drug use.
The saint.
You must remember that up to a certain point – that great and beautiful point – he claimed to be the most honest sportsman in the world, having won the Tour de France more times than any other human being.
He swore on his children's blood that he never used performance-enhancing drugs.
He ended up becoming a fraud. A liar, an unscrupulous man who believed his own lies because he needed them as truths to justify his actions.
Therefore, I repeat…
I'm sorry.
You can't catch those people.
They are the kings of their own (and false) truth.
AN ADDENDUM
What is a picture of Lindsay Lohan doing in this response?
Well, she's my main role model when it comes to answers related to psychology.
Lindsay doesn't seem like a pathological liar to me. In fact, I think she's quite the opposite: too honest and hiding very little.
She exposes herself a lot and leaves us with the lesson that being too honest can also harm us.
But I prefer this to the narcissistic liars in the cases above.