This is hard for me to write about, but I'm considering a composite theory augmented by a comment that someone made on HLN last week. Pardon me if all of this has been posted before.
First, I doubt that chloroform was involved in Caylee's death. Something suggests to me that there is another explanation for the traces of chloroform found in the trunk of the car--degradation of plastics, maybe, or other bands on the gas chromatograph associated with human decomposition that cause false positivity for (or create small amounts of) chloroform. Don't be surprised if a forensic pathologist/chemist for the defense shows up on the stand to discredit chloroform as a causative agent of Caylee's death.
Furthermore, has anyone offered a plausible explanation where Casey could have bought or otherwise obtained enough chloroform to kill Caylee? (It takes far more than a handkerchief's amount to anesthetize someone--that's a fiction reserved for the silent movie era.) It's not an easy chemical to obtain without a legitimate reason, and I'm sure LE has combed through any associations by which she could have obtained it. (The suggestion that Casey decided one day to become an amateur pharmaceutical chemist to synthesize it from other compounds in order to sedate or kill Caylee is rather unlikely, I think.)
I think Casey killed Caylee at the Anthony home by suffocation or drowning...but why the duct tape? And, how easy would it be to smother a nearly three year old child simply by applying duct tape to their face? That sounds pretty difficult to me. IMO, Casey had to have used brute force to kill her otherwise. I don't think duct tape alone would be enough to smother a toddler struggling to breathe unless they had doses of medication (and, not chloroform, BTW) approaching that of an anesthetized patient in an operating room.
IMO, the duct tape came later when Caylee began to emit fluids from her mouth and nose after she died, probably within 24-48 hours after her death. Casey didn't realize that after Caylee's death, there would be no obstruction to the flow of fluids from her stomach and upper airway that would normally be contained in her body when she was alive. She didn't have an immediate plan for disposing of her, but when the trunk was becoming a bit of a mess she had to find a rapid and effective way of dealing with this problem.
Hence the duct tape: several pieces applied copiously. At least one and possibly two strips were applied over Caylee's nares, the third wound circumferentially around her skull to stop the leak from her mouth. The circumferential segment held Caylee's jaw in place until she was found.
My take is that neither chloroform or duct tape were the primary causes of Caylee's death. It's hard for me to accept that either were the first agents employed to take this poor little girl's life away from her.