I used to play poker for a living. I think I enjoy sales too much, to risk going back. I also don't like the direction the game is going.
I might be able to provide some perspective. You first analyze the situation independent of the eyewitness testimonies.
Now you think about if a liar would lie in the specific situation or not, and then how likely they are to think you believe their bullshit.
Body language speaks a lot . If I was heads up and faced a tough decision in poker, one decision usually benefits the other person more than the other decision.
If somebody wants you to fold to a bet, they will often stare you down, have tense facial muscles and try to look big. If they want a call, they will try to look a bit intimidated. After a while a good player learns to look like they don't give a fuck what you do. A great player, actually doesn't give a fuck what you do, and it comes across.
So this is a situation where I would say, don't trust a person liar or not. Trust the person's body language.
What about emotions.
This is a rare tell, but because it is emotional you can trust it 100% of the time. A player pushes all his chips in the middle and you have a good hand, but you notice that his hands are quivering and they have not been quivering before.
To some naive players this may look like fear. However this is one of those uncontrollable tells. He is quivering from a rush of adrenaline. He knows he will win a bunch of money if you call. It doesn't matter how good your hand is, just fold. That is unless he is a total mouth breather who thinks things are really great, but aren't. Those types of mouth breathers are incredibly rare.
You can trust a liars emotions almost always.
What about words. If you know their motive and their personality, you can figure out what words would be honest or dishonest given the situation.
If you a person is betting into you the flop turn and river in poker and throw their hand away, so you don't see it at the end and they claim they had you beat until the 3rd spade came. You can tell they are lying and just trying to bluff you off a pot.
If you ask the person what they folded after they folded and the hand is over. They'll usually be honest.
The situation is what you judge first and then you look at emotions, and body language and then words.
If it is Christmas time and you ask the person their waist size and they say 36, you can trust it more than if it is January 15th and a person just gave up on their diet and you ask them their waist size.