Unfortunately for David, it would not take much for someone on a jury to look at his behavior and make a connection to a sociopath. And if they believe he's a sociopath, they might believe that he would be capable of murder. There are too many examples of Davids words and behavior that fits into the description:
Profile of the Sociopath
I have to agree with Afterdark completely. That's what, I think, many of us who know David have been trying to say that many who don't know him don't understand. I said it before - I know a fairly large number of people in the dive community who will call David arrogant - and in fact, David has used the word to describe himself. He's well aware that others find him arrogant, and yet he is who he is. It's a little late to ask him to change that. Judging his character - which is quite "different" than the vast majority of people I know - against what is "normal" to most people simply isn't realistic. He is the way he is because of how he's dealt with how he grew up. Which is exactly why the testimony of his psychologist SHOULD have been allowed to be brought before the jury. Look - David is someone who's easier to dislike than a lot of people - if you never take the time to get below the surface.
But the question that comes from that is very key....can you/should you convict someone of murder simply because he's arrogant??? can you/should you convict someone of murder because you don't like him???
In looking at your link on the traits of a sociopath, K-girl, I really don't see anything that applies to David.
Glibness and Superficial Charm - I wouldn't say that David is particularly charming or glib...he is what he is. And Afterdark described him accurately - when he was pre-occupied, he often came across as cold and abrupt - hardly what one could call "charming."
Manipulative and Conning - I've never seen David as being manipulative - he's pretty open about what he wants and how he goes about getting it. I've certainly never seen him dominate or humiliate anyone.
Grandiose Sense of Self - Can't say as I've ever seen his self-esteem to be any higher than anyone else's...
Pathological Lying - I don't think that David has lied any more or less than anyone else and I most definitely wouldn't call it pathological. Did he explore the possibility of an affair while he was married to Shelley? Yes. And obviously, that took some lies. But I know a lot of people who've lied much more about much worse...and no one's calling them sociopaths....
Lack of Remorse, Shame or Guilt A deep seated rage, which is split off and repressed, is at their core. Does not see others around them as people, but only as targets and opportunities. Instead of friends, they have victims and accomplices who end up as victims. The end always justifies the means and they let nothing stand in their way. - I'm leaving this explanation in because I think it's important. David has a LOT of longstanding friends who by no means are "victims," "targets" or "opportunities." He most assuredly does see those around him as real live people - he just limits the number of people that he lets into his inner circle of trusted friends.
Shallow Emotions - Very much untrue.
Incapacity for Love - Again - very much untrue.
Need for Stimulation - Unless one calls diving "living on the edge" I don't think that that's even remotely true. And I don't recall anyone who knows of David ever having a single violent outburst or ever physically hurting anyone - ever.
Callousness/Lack of Empathy - I can see that people might interpret things he's said as callous or lacking empathy, but I would say that they come more from his inabiliity to handle painful events well.
Poor Behavioral Controls/Impulsive Nature - completely untrue.
Early Behavior Problems/Juvenile Delinquency - I never knew him as a child, but to my knowledge, this was never reported as a problem.
Irresponsibility/Unreliability - I can't say that I've ever known David to be irresponsible or unreliable as a person. I do know that he felt that a certified experienced diver should be capable of diving solo if they felt comfortable with doing so - we had that discussion once.
Promiscuous Sexual Behavior/Infidelity - Although he was attracted to Mary Basler, by both their accounts, this was not taken to physical infidelity during his marriage to Shelley and in fact, a letter from David to Mary Basler indicated that her rebuffing of his advances caused him to go back and get to work on renewing his marriage with Shelley. To my knowledge he has not been "promiscuous" by any stretch.
Lack of Realistic Life Plan/Parasitic Lifestyle - I can't say that David has a poor work ethic, since he worked his butt off at the shop to make a go of it. He's lived in two places his entire adult life, to my knowledge and they were both in RI...so he certainly didn't move around a lot....
Criminal or Entrepreneurial Versatility - Definitely untrue. If David had wanted to leave to avoid prosecution, he certainly could've done so during the 10 years after Shelley's death. He did not have to return to the very small island community in which both he and his deceased wife's parents lived after her death. He could easily have taken the money and moved to another country where there were no extradition laws. He did not. Even after the civil verdict, he stayed here. He was arrested exactly where one would expect to find him - behind the counter of the dive shop.