RSBM. I agree with your first and last statements, but IMO your example and your conclusion from it is flawed. There WAS evidence including testimony that supported the defense argument in the CA case.
Defense attorneys cannot argue based on speculation, and juries are instructed in all cases that they are not to indulge in speculation when deciding whether the prosecution has proved its case.
IIRC, the prosecution in CA's case sought an order preventing the defense from arguing accidental drowning as the cause of Caylee's death, arguing as you do that supporting evidence was insufficient. The judge ruled that such an argument would be allowed based on inferences from admitted evidence, supported by witness testimony.
In addition, the accidental death argument was far from the only reason the jury could reasonably find CA not guilty. The defense vigorously attacked every bit of the prosecution's evidence, including the autopsy which was manifestly flawed. The main argument of the defense was that the prosecution's evidence for murder was weak. The accidental death argument could only succeed if the jury concluded that the evidence for murder was equivocal at best, IMO.
In the end, the CA jury was able to set aside their assessment of the defendant's (virtually nonexistent) character and look at the prosecution's evidence, which they found to be insufficient to prove guilt beyond a reasonable doubt.
This forum is not the place to argue the merits of the CA case and I do not want to start a general debate on the outcome or the process. But without this limited reminder of the facts in that case, I cannot respond to your citation of it to support your conclusion that defense attorneys can submit to the jury arguments based on speculation alone.
