Man, he sure wanted her dead, didn't he? From the autopsy, I am even more sure that it was her husband who killed her. Talk about overkill. There was no break-in; no robbery; no rape and extreme overkill. Who else who was very close to Michelle would want her dead? How many people knew that her husband left late that night for a business trip? If the husband wasn't the murderer, that sure left a very small window of opportunity for another killer, didn't it? Heck, she had a friend over until very late that night.
I believe that he underestimated how strong his wife really was. Remember, she was very athletic. He probably did have marks on his hands and arms. I wonder if the cops were able to observe anything when he came to retrieve his daughter the next day.
Of course, I feel that he caught her off guard. That wasn't enough to subdue her right away. He in his mind thought that he could strangle her and that would be it. I wonder if he was prepared with a weapon or just picked up something heavy in the room? Could a flashlight make that many deep lacerations to her head and even crack her skull? I was thinking of something heavier with a sharper edge. I guess I have to defer to Baden, though. He's the expert.