Jury Instructions on Circumstantial Evidence

The jury instruction in the Lewis Libby lying trial includes a boilerplate instruction on the legal (in)difference between direct and circumstantial evidence:

DIRECT AND CIRCUMSTANTIAL EVIDENCE
There are two types of evidence from which you may find the truth as to the facts of a case -- direct evidence and circumstantial evidence. When a witness states that he or she has actual knowledge of a fact, such as an eyewitness, that witness’s testimony is direct evidence. A chain of facts and circumstances indicating the guilt or innocence of the defendant is circumstantial evidence. The law makes no distinction between the weight you should give to either kind of evidence, nor does circumstantial evidence require a greater degree of certainty than direct evidence. In reaching a verdict in this case, you should weigh all of the evidence presented, both direct and circumstantial.

Generally, people who exclaim "It's all just circumstantial evidence" don't know what they are talking about.