The court of law states otherwise.
Most popular example: Scott Peterson convicted solely on circumstantial evidence. Not a single piece of direct evidence.
http://www.foxnews.com/story/0,2933,138362,00.html
Cases can still be proven beyond a reasonable doubt if there is enough circumstantial evidence that together show that the defendant was the only one who could have possibly done it beyond a reasonable doubt.
Here is more information how that is possible and how a Supreme Court ruling allows it:
http://en.wikipedia.org/wiki/Circumstantial_evidence
http://legal-dictionary.thefreediction
You've completely misread what I wrote. I never said there had to be any direct evidence.
Whatever evidence is provided, it must prove the case beyond a reasonable doubt.
So your statement that the only possible verdict is "not guilty" is incorrect. Even if she is found "not guilty"--it isn't necessarily because the evidence is only circumstantial.
Also of important note in that case--some try to say it was some kind of accident, which may have been the case. Many opinions on what type of accident it may have been have been stated.
In the state of Florida--if the "accidental death" was caused by "abuse of the child"--for example, the idea that she was given chloroform (not proven with direct evidence), then that can lead to a Felony murder conviction. Someone posted the actual law on the CA thread. Too tired to search it out right now.
Lastly--the state doesn't have to show pre-meditation either. Some form the opinion that she can't be convicted because the state cannot prove any premeditation. It isn't required though it certainly helps if they can show it.