The kind of "premeditation" needed to prove first-degree murder is just basically enough time to realize what you're doing and stop. The type of "premeditation" needed for the aggravating circumstance is cold, calculating premeditation which means actually thinking about it and planning.
Thanks AZL ~ That's always been my understanding of it also.
So, the "enough time" could simply be argued that the amount of time that it took her to go to wherever the duct tape was at at the time. Whether it was in the garage, the kitchen, under the bed, or right next to her; for instance on the nightstand where she may have left it last from using it for something else. {not at all saying it WAS on the nightstand, using this an example}
The simple fact that she reached for, or, took the time to go get it, makes it premediated because she KNEW what she was going to do with it.
The second part of your explanation could be argued and or suggested then, that this same time that it took her to go get the duct tape, knowing what she was going to do with it when she returned.
There is a time frame of going to or reaching for the duct tape before placing it on Caylee.
Reaching over to the "nightstand", or, going to to garage, etc, gives her time to "think" about her actions, regardless if the lapse of time is 2 seconds or 2 minutes.
She knew what she would do with it when it was in her hands, and, she followed through with it.
This would result in the Calculating Premediation, IMO, if I've understood the meaning as put forth, and, from other cases and explanations.
She had also had "time" once she returned to change her mind.
She tore off 3 peices at least that went over Caylee's mouth. Whether those were placed all at once, or, one, then tear off peice number two, place it, then tear off peice number three. She had "time" between each peice to change her mind and STOP.