Understand that in a matter of moments you can find a number of YouTube videos and books from people claiming to be body language experts and whom purport they can tell when someone is lying. There is an abundance of unsubstantiated lore out there when it comes to deception. More than a few so-called experts regularly make false claims.
For example, listen carefully the next time you hear someone say “[This] means he is probably lying.” Some of the self-proclaimed pundits will use the words: probably, may, could be. They won’t commit to the validity of that claim and cover their tracks by sliding in that it probably means they aren’t being truthful.
Or worse yet “[This] means he is lying.” Nope, not necessarily. [This] could mean he is uncomfortable (we certainly know how uncomfortable it can if you think you will not be believed, even when it is the truth). [This] could also be his baseline – the way he normally behaves.
I recently saw a video where the “expert” was trying to say that when the witness or juror in a court case is sworn in, she looks at how the person holds their right hand. She made all sorts of claims that wide fingers meant they were scared; closed fingers meant you’d have to pry information out; curled hand means they will not be truthful. Hogwash! She failed to take into consideration the person could have arthritic hands, or tendon damage or could have been raking leaves for hours and simply had sore hands.
The same “jury expert” announced she is used for voir dire proceedings (jury selection) and that she can tell what one is thinking! That’s quite a claim, unless she had a crystal ball or was somehow credentialed in mind reading. Processionals who study human behavior can be a great asset in alerting you as to areas you want to probe further. True professionals can provide beneficial information to help your case – but read minds and tell you absolutely someone is lying is not a credible claim.
In a high stakes situation you need better than could be or probably. Concealed Statements assessments are based on psychological models of truth and scientific studies, not popular myths. Accurate behavior assessments can point out areas of concern or issues you will want to delve into further.
We can tell you how someone may be feeling, but not what someone is thinking. Without ground truth already available, it would be professionally irresponsible to proclaim someone is lying. Beware if someone tries to tell you that a particular expressions, action or verbal style definitively communicates something definitive. What it may communicate is a need to dig deeper.