I have a suspicion that the prosecution does not have the 'slam dunk' 1st degree murder case they had expected. I think they charged KC hoping that either Caylee's body would be found early enough to be able to yield up sufficient evidence to support the charge, or that KC would crack after being incarcerated for a while. Neither has happened.
IMO unless they get, or have got, more evidence to support a charge of premeditated murder than we have seen so far, they will struggle to build a convincing storyline that cannot be easily challenged by the defence. In particular, I think they may have initially placed too much reliance on the chloroform evidence (PC searches + forensics from the car) as potential proof of planning and intent, but we have already seen for ourselves how this evidence can be quite convincingly and reasonably explained away. Even the most damning evidence to date (the duct tape) may only prove that KC applied it where it was found, but not the 'when' and the 'why'.
I may be wrong, but my suspicions were aroused when I observed during the last motions hearing that the female prosecutor (can't remember her name) quickly jumped in to delay the next hearing date proposed by the judge and to state that they would not be ready until at least the end of the year, if then. I think they are hoping that the prospect of many more months solitary confinement will make KC crack. In the meantime, there may well be some more pressure applied via 'sources close to the investigation'.