What is meant?

Word choices are pretty important when speaking.  Early on in the second half of the 20th century, linguistics became a full-fledged discipline of study apart from psychology although before that time the two were indelibly linked.  One of the first matters of interest to explore was to find a universal grammar.  That ended up being a street that has branched many times as it has been explored.  But, the second matter of interest was a part of Noam Chomsky's work (the father of modern linguistics wrote a dissertation that spawned transformational grammar) that went unresearched and left for others to investigate, the area of semantics.  Now, of course, a number of good theories exist as to the nature and generation of meaning assigned to words.

Eventually, forensic linguistics would intersect with the study of semantics and produce tailored theories and methods for delineating between truth and deception.  Some of the first methods developed worked with word choices.  People usually think of vocabulary when mentioning word choices, and sometimes that is the case.  But, many times it has to do with the placement of adverbs in particular positions in a sentence or the type of conjugation of a verb.  The linguist working with detectives on the Susan Smith case a number of years ago, for instance, noticed that she spoke immediately following the drowning of her children in past tense.  Most people would have spoken in present tense since they would not have been used to the idea of their children being dead yet.

Because all words have assigned meanings to them by society, the choices people make can definitely be important.  In casual conversation, people don't really think too much about the words being spoken because they are speaking for the reason of merely communicating information.  But, when people think they are being evaluated, judged, or taken more seriously for some reason than casual conversation allows for, then they become much more aware of the words they are using and start making more particular choices.

The tricky part sometimes about evaluation of word choices is that society allows words to have double and triple meanings.  Deciphering meaning sometimes can be very context dependent.  An example from the famous DeLorean car case in New York illustrates this concept perfectly.  The person who broke the case  was told that if he did so, the defendant would kill him.  Sometimes, the word kill means to take a life, but it can also be used to metaphorically express anger without any action taking place.  Attorneys worked hard to show the context was a case of the latter, not the former meaning.  The defendant for this and other reasons was found innocent.

People say things all the time that they don't mean to follow through on.  So, eventually, everything boils down to words being figures of speech or literal in nature.  Once that hurdle is discovered, then the business of truth or deception can be taken up.