As much as I depsise Casey at this moment...and it is very much...I have to agree that reality is we do not know the reasoning behind the sticker it could be due to regret/guilt or it could have been done in spite. We just don't know at this point....may never.
The Duct tape will be far more important for the prosectuion, as you do not accidently duct tape a child. Not to mention the mounds of other evidence, IMO we have yet to see the "real goods" in this case...there is much more to come and IMO I believe the state has what they need for Murder One, but as this point that is all it is just an opinion.