Circumstantial evidence is usually not enough to land a successful prosecution, but when it start's piling up (rather much like the mountain of crap Casey's in), then you have a pretty good connection between her and the victim. However, I have yet to see a murder weapon, and I have yet to see a motive. There's the chloroform in Casey's car (and the decomp chemicals, which are a suspicious pair), and the blanket missing from the kid's crib found near the body, but that's pretty much all I can find. The defense could say the kid was stolen in the night, they could say that the car was jacked in the process, or SOMETHING. If they want to win this case, they need rock-hard proof that shows that Casey was there when the murder happened. And with every day, evidence will be harder to find.

Sadly, this may very much turn out like the O.J. Simpson Trial - We'll have to wait until she does something else before we can nail her (judicially, not sexually).