I think they're going to go with Choloroform accidentally killing Caylee. She'd used it before (the real kind, not homemade) and it worked. ICA was able to continue her partying and hanging out with friends while Caylee was knocked out. She grew tired of having to pay for it so she googled how to make it on her own. She used the homemade kind for the first time on June 16th and it accidentally killed her. ICA paniced and didn't know what to do, so she lied until she could lie no more. She was afraid of goign to jail, was afriad of her parents, afraid of losing Tony, so she had no choice but to lie.
How's that sound?