The prosecutors blew it, they were never able to determine cause of death...see
http://www.foxnews.com/on-air/on-the-record/transcript/casey-anthony-case-csi-look-forensic-evidence
And then the body was cremated, to where no further forensics could be performed..the whole thing stinks...
Bull crap, you do not need to prove the cause of death, what do you do when there is no body. The kid was missing her sorry ass slut of a mother did not report it. End of case.