The pathological narcissists and sociopath I suspect I've known, and the majority of case histories w which I'm familiar, all have a clear identifiable history which anyone could recognize to which their lack of empathy can be linked or attributed. From what we've learned, there's been very little "positive and consistent" about KC's parenting or upbringing whatsoever. KC never was held accountable but sadly had her outrageously bad behavior rescued, excused and enabled one too many times, until the ultimate price was paid--by CAYLEE.
Interestingly, narcissism in particular is said to result specifically from a controlling parent's simultaneous extremes of coddling (over-indulgence, excessive smothering) AND "beating the bad" (overly harsh and critical inacceptance of mistakes). That is to say when a child is deprived of both appropriate boundaries and discipline, AND permission to fail; when neither humility, nor reasonable limits, correction and consequences are provided, in balance, at critical stages. As I said, there are a number of factors--one of which is environmental. And while all else--the role of parental or other influences from one child to another--may appear to be equal or identical, we're only able to observe as outsiders and this subjective experience varies dramatically even between siblings.
After CA had been in collusion w KC's lies, letting KC off for stealing from her and virtually every other offense for 22 years, CA finally decides to act like a parent and draws the line that Father's Day--finally threatening to put KC out and hold her daughter accountable for the first time in her life. So in an odd sense KC's right then when she tells LA, "I should've been stopped a long time ago." A statement which reveals both a weakness of conscience, and a consciousness of guilt--beyond which the law will be essentially unconcerned w such nuances, coexisting disorders, contributing factors, or how KC may have come to be the (defiant, irresponsible, blameshifting, deceitful, seemingly indifferent) person she appears to sadly have become... but I'm looking here beyond strictly legally (it belongs more rightly in psych thread but since you brought it up...) at how controlling her mother is. And the anger and emotions people feel are not limited to KC.
Narcissistic parent- vs child-centered parenting produces narcisstic children. People w NPD are compulsive, serial liars. Witness KC's envy, exploitation, sense of entitlement, lack of empathy, false inflated self... There is nothing in the way she has behaved that is remotely how a mature, secure, rational, reasonable or responsible ADULT would act. But it may have been almost a self-fulfilling prophecy the way CA constantly was telling her what a bad mother she is. Then when you read the interview w her brother after she's pressed for the truth what does she keep repeating over and over? "Maybe Mom's right, maybe I am an unfit mother afterall," That's always stuck in my mind and was a flashing neon sign to me--she musters as close as she can to telling the truth. She also makes similar statements to LE, "I know my mother will NEVER forgive me," but soon reverts to self-deprecating ("Maybe I'm just a spiteful b*") and by the time CA returns, resumes the fabricating. IMO it was, and is still, CA's reaction she fears and whom she was lying to protect, not LE. Definitely some kind of emotional caretaking and enmeshment going on there. Much of which might be avoided if raised in an environment instead of GRACE (for mistakes) and TRUTH (consequences, and accountability). Instead it seems deceit, permissiveness, self-preservation, and enablement were the order of the day and well learned, while appearances were given more importance than operating in reality.
We can call KC an evil monster and search no farther for understanding; or we can hold her harmless because she's "sick" and "can't help it," but the truth lies somewhere between. And it might help if she was given permission by her mother to stop lying.
There is nothing that can be done now to bring back Caylee nor really ever reverse the damage that one disturbed, narcisstic young woman has already heaped upon so many. But thank God for all of the psychiatrists, clergyman, educators and laypeople who do seek to understand the causes of personality disorders, or the making of a sociopath--and to end the cycle of suffering. The only way I can see to overcome that in the future is by hopefully educating parents as well as those in the counseling and therapy community toward a greater awareness of child and personality development. I am very sorry to hear of the drama surrounding your cousin, the heartache and suffering of your family's ongoing ordeal. But I can not and will never accept the theory of "demon seeds" or "psycho genes," it's a far too fatalistic and dismal prospect.
Sociopaths aren't born. And you can't do battle with a hidden "enemy." JMHO