Reposting this response from the tail end of 8 (thanks Sami) and as promised:
Scandi said:
... Each killer had something he wanted to accomplish above and beyond the actual killing. With Robb it was wiping out her identity. He left her virtually with no face. He despised or really hated her I think. With Michelle's murder, he wanted to wipe out the control her brain had on him. So smart, decicive in details and most likely very logical but pointed in her thoughts, he wanted to especially kill that part of who she was. With both men, this is what was the main threat to their own future wellbeing. And that is why they each killed the way they did.
Just thinkin' away! LOL
Scandi, you raise a point similar to (or remind me of) a few days ago. I don't know if you saw my post, but the thread closed and I had to run ... but what I wrote about was what I thought about the relationships between Michelle and Jason, Michelle and her father, Jason and his father, and Jason and his stepfather.
I suspect that Michelle's natural father was abusive and this is supported by Michelle, Meredith (her myspace) and Linda Fisher's reluctance to associate with him. If this is true, Michelle would have made a point of trying to avoid men like that, although it would have been in her nature to gravitate towards those types of men. I think that women are attracted towards men with similar characteristics as fathers, boyfriends, husbands; even if they are sometimes domineering - they can't help but be attracted to the confident, golden-boy, facade that is the double-edged sword.
It is also possible that Jason's father was domineering. I'm speculating on this because his stepfather has clearly been telling Jason what to do and what not to do. In fact, he has taken charge of Jason regarding getting a lawyer and even with the media, to some degree. He probably told Jason to come home until it all blows over and Jason listened. I think you asked whether he might be in law enforcement. I think at the very least he is a vietnam war vet and prone to giving direction to people. I also think Jason's natural father could be equally domineering if he were in the picture.
I think it's possible that both Michelle and Jason wanted to avoid domineering or abusive people and had probably discussed the presence of those personality types in their families. However, I also think that they were both a little prone to interacting with domineering personalities in ways that may have been both exciting and unhealthy - and I'm completely speculating here. I wonder if they both wanted to get away from people like that and found each other, but had unfortunately absorbed some of the personality traits common in abusive or domineering people.
If I recall, Michelle was instantly attracted to Jason in the bar ... she was the centre of the party and he was the wall flower. Jason was withdrawn, Michelle was outgoing ... but both personality traits were probably coping mechanisms for a social imbalance that they felt in their childhoods. Much as they wanted to avoid domineering people, they would have been drawn to each other. A certain competitiveness would have seeped into their lives in terms of academic credentials, financial superiority, ability to manage it all, day to day conversation with jokes being both jokes and put-downs ... funny put-downs but not really funny. I think that they were attracted to the dangerous part of each other but believed they could control it, or perhaps control it in each other.
I can see that this combination would have worked on the facade - that golden boy/golden life/golden future would have been very attractive to everyone (including friends of Michelle that sought to boost their own self-esteem by seducing her husband). I also suspect that beneath the facade there was a lot of tension because it appears that Michelle was able to manage it all, was more financially (career) stable and definitely had the "made for success" academic credentials.
Michelle, like Jason, was very bright and she would have sensed a marital problem in August, just prior to his fling with her sorority sister. Michelle's pregnancy may have been related to a sense that Jason was straying (just speculating) because the timing was right.
I can see that Jason would have had tension building for a long time; probably since the time Michelle became pregnant, he changed jobs, he had the fling/affair, and was he faced with the prospect of supporting his family without Michelle's income (up against the wall). I also think that he was afraid of any jokes or redicule that would have resulted from him floundering. I think he would have lost face if he couldn't pull it off.
Okay, that's a little more long winded than the first time I wrote it, but the gist is there ... obliterating one's partner due to a fear of one's own failure being reflected by the partner.
In my opinion, Scott Peterson suffered from this problem (his business was failing with a baby on the way), Mark Hacking had the same problem (about to be revealed as an academic fraud and a baby on the way) ... and I haven't followed enough cases to really make more connections but I bet you can name a few more. Maybe that's all it comes down to with men that murder their pregnant wives ... just a really big fear of failure and loss of "golden boy status" in the eyes of their friends, family, and lover - who have put them on a pedestal they never felt they deserved.