What we know

One habit that detectives and attorneys have that leaves them blind to the truth is to ignore a very obvious principle.  Everyone knows that people speak more about matters they know than matters they don't know.  Duh, right?

But detectives and attorneys fail to ask for comments on all relevant topics.  As a result. matters a person knows versus matters a person doesn't know goes unknown.  That unknown information could prove to be damaging.  If a suspect or witness doesn't know much about something, then the topic is harmless. It would be the topics most known that need exploring and probing.  That will be where deception is taking place.

More generally, people new to a relationship should adopt the same philosophy.  A partner is less likely to exploit what he or she doesn't know, more likely to exploit what he or she knows a great deal about.  Being aware of the areas of someone else's knowledge base makes one aware not to open up without trusting the person or situation.  That limits the amount of damage a malicious soul (or uncaring) can inflict.

In legal matters, areas of knowledge are like enemies.  And as Michael Corleone has said, "Keep your friends close and your enemies closer," (Godfather, Part II, 1974).  Areas of great knowledge unprobed are very dangerous.  A lot of truths, half-truths, hedges, and deception can take place in such vast unexplored areas.  It should always be the case for attorneys in depositions, voir dire, case presentation, and witness examination to explore all the areas of strength an individual has.  Therein lies the truth (and his or her deception) about a matter.