Correct. To conclude the duct tape was the mechanism of death or the cause of death is speculation -- juries are not permitted to speculate.
I didn't say the duct tape was the cause of death. After taping, KC could have strangled Caylee to make it go quicker. She could have shaken Caylee. But, those are semantics.
Bottom line--When KC put layers of duct tape over Caylee's face and nose, she was trying to kill Caylee. It was deliberate and intentional.