There are two ways that I catch liars and identify the motives of fake people - in their poor multi tasking ability or in the priorities they reveal about themselves when they involve themselves in choices where multi tasking is required.
Like my female cousin did not want to offend my male cousin who was pretending to date girl he did not respect or like because he wanted physical benefits, and not wanting to offend my male cousin she told me she did not care if my male cousin pretended to love a girl who meant nothing to him because it’s none of her business. In trying to protect herself from appearing socially uncooperative with our male cousin, she exposed herself as somebody who does not value honesty enough to intervene in the moral decisions of her family, meaning she is an explicated sycophant and flatterer and not a reliable testifier who can be trusted to act courteously when she is not being monitored by others.
I knew another guy who was also a pathological liar; and everybody knew he was a liar, because when we got into disagreements, he would spend so much time trying to defend himself against one social accusation, that he ended up exposing himself to competing an alternate social accusations in the process, for example Donald Trump opposes illegal immigration but he also supports racism and tax fraud and adultery and lying, a liar will forget about the other crimes Trump has committed and focus only on that one issue, exposing himself as somebody who condones the other crimes he commits.
A liar reveals their priorities to you when you force them into situations where they have to balance multiple pros and cons at the same and have to choose which cons or pros to sacrifice to achieve their ends, somebody who operates by self referent is encoding or socially referent encoding instead of by objective truth and morality, will behave in a way that is unacceptable or contradictory, which is how they get exposed as liars, this is how most liars get caught.
The bible says liars always get caught, it’s just a matter of time.