There was no forensic or physical evidence tying Casey Anthony to the crime. Do I think she is guilty, probably. Did the prosecution prove it....Hell No!!!!!!! The autopsy done on Caylee could not determine the cause of death....and no fingerprints or DNA or other physical evidence was found on her or the duct tape found on her. If you can't prove the cause of death, how can you convict someone of murder or manslaughter?
I think the way the media (especially Nancy Grace) covered this case from it's beginnings in 2008 was a disgrace. Nancy Grace tried and convicted Casey from the beginning........the jury heard ONLY the evidence presented at the trial and did not hear all the opinions, commentary and hyperbole of the media.
Is our system perfect? No. But it is the best system out there.