I know nothing about the Casey Anthony case other than she was found not guilty of the murder of her two-year old daughter after a lengthy trial in Florida that captured the attention of much of the nation thanks to the intense coverage the trial received in the media, particularly on TV. Now there is much water cooler discussion about the correctness of the jury verdict. Having tried a couple of dozen criminal cases in a prior career, I know better than to speculate on the reasons why a trial ended as it did. Every criminal jury trial, no matter what the charge, has its own dynamic and anyone outside of the crucible of that trial has no idea of how a jury reaches a decision – for that matter, even the people involved in the trial are often stunned by the verdict.

When it comes to criminal trials, however, the concept of “proof beyond a reasonable doubt” is a very powerful thing. The defense has no obligation to prove anything – my experience is that when the defense does try to prove something, it gets itself into trouble – and so the defense can just sit back and raise questions about the prosecution’s proof. Because “proof beyond a reasonable doubt” defies a clear, easily applied definition, it becomes a concept completely personal to each member of the jury; hence the unexplainable conclusions that are reached.

In Massachusetts, a judge does try to define, or at least describe, proof beyond a reasonable doubt to the jury. The language used is taken almost verbatim from an 1850 case, Commonwealth v Webster. See how well you understand its meaning:

The burden is on the Commonwealth to prove beyond a reasonable doubt that the defendant is guilty of the charge(s) made against him (her).

Then what is reasonable doubt? It is a term often used, probably pretty well understood, but not easily defined. It is not mere possible doubt; because every thing relating to human affairs, and depending on . . . evidence, is open to some possible or imaginary doubt. It is that state of the case, which, after the entire comparison and consideration of all the evidence, leaves the minds of jurors in that condition that they cannot say they feel an abiding conviction, to a moral certainty, of the truth of the charge.

The burden of proof is upon the prosecutor. All the presumptions of law independent of evidence are in favor of innocence; and every person is presumed to be innocent until he is proved guilty. If upon such proof there is reasonable doubt remaining, the accused is entitled to the benefit of it by an acquittal.
For it is not sufficient to establish a probability, though a strong one arising from the doctrine of chances, that the fact charged is more likely to be true than the contrary; but the evidence must establish the truth of the fact to a reasonable and moral certainty; a certainty that convinces and directs the understanding, and satisfies the reason and judgment, of those who are bound to act conscientiously upon it. This we take to be proof beyond reasonable doubt . . . .