body: I have noticed that in order to discredit a witness, instead of simply saying someone is a liar, the defense will call the person a "fantasist". 
  
  
  This brings to mind some child-like person going on adventures with their imaginary friends. Basically they're saying they're crazy.
  
  
  Personally I've never met a "fantasist" in real life. I wonder do lawyers really think that a person is crazy or is this just one of their arguments in their itinerary to discredit a witness.
  
  
  I mean unless someone is completely insane they surely have a reason for lying. Even a fantasist can surely separate real life from their fantasies? And if they were really insane wouldn't they be in a mental institution?
  
  
  Is this a common defense to use on an accuser? Is it taught in law school to use this defense?
  
  
  
title: Where is the "fantasist" defense taught?