I think that all three were in play - dear hubby grabbed her by the throat, pounded her head against the wall, bashing her brain around, and then squeezed until she was gurgling on the floor struggling for breath. Or maybe people would rather believe Michael: “I found her on floor...don’t know what happened...”
20 years later the execution was complete.
And Mikey failed to perform CPR even though he was trained to.
Also, there is direct testimony from Terri's brother and best friend that she was planning to leave Mikey because of abuse and she had had these conversations as recently as the afternoon before her injury.
And do not forget that Mikey hired an attorney within 48 hours of Terri's injury which would lead a reasonable person to conclude that he was afraid of what would happen if she recovered.