I think that it'll be tough for Baez to get Casey off scott free, but barring powerful forensic evidence or a major investigative breakthrough, I think that Baez has a reasonable chance of minimizing Casey's sentence.
Without the above, Casey can always fall back on the "it was an entire accident that I had nothing to do with and then I lied because I panicked and was stressed out over the accidental and tragic death of my Caylee" theory. If LE accepts this plea, they very well can't charge Casey for Caylee's death, having agreed that her death was accidental, because accidents do happen, even unfortunate and tragic accidents.
LE needs evidence of the cause of death as well as the death itself in order to really put Casey to the screws.
They can still try Casey for her alleged responsibility in the death of Caylee, but without proof of the cause of death, their case is that much weaker. Reasonable doubt over the cause of death will go a long way in determining the possible length of Casey's jail sentence.