Or both.
Disordered personalities are sometimes drawn to psychology and psychiatry themselves as a subconscious attempt at self-medicating. Anyone who might be familiar with symptoms of NPD might've noticed a great deal of those traits with the Doc's testimony.
And psychopaths can and will be honest, though its often believed they can't or won't, but ONLY if doing so is in their own personal best interests. Obviously that's not the case here.
IME, the
only way to rattle a psychopath is to get under their skin. You can't do that in a methodical, predictable manner. They're expecting that and will simply manipulate around it. Instead, you have to hold them accountable for their
every word, each and every inconsistency, every action, no matter how seemingly benign - and
that absolutely infuriates them, which exposes more of the disorder and makes it even
more difficult to question them, because they become combative and defiant.
People aren't supposed to disbelieve a psychopath's account - it's against the natural order of things in their world. And Juan is likely one of very few in her life who has done that.