I'm glad you say "looks like", Jon, because that doesn't indicate which order the wounds were inflicted - ALL the wounds were caused during life. That aside, I still struggle with the idea of his using two knives, one 37 times and the other only once.
Your struggle hasn't gone unnoticed Sam, although my post citing the problems with a single assailant and 2 knives surely has.
Killeen states that the wound to her heart was sufficient to cause death.
He didn't say it was sufficient to cause instant death, though. I'm not being picky, by the way: being stabbed in the heart would almost certainly be fatal, but it need not kill a person right away. Indeed, it's even possible to survive.