Some lessons can only be learned in hindsight. One of the claims that the
anthrax letters came from Iraq was because of the presence of silicon to make it
more easily air borne. So it turns out that the person that made this claim is
an expert but in a different area. Of course, since what he said is what people
wanted to hear his views were widely publicized and believed

Lesson 1: People’s area of expertise matters, not just that they are an expert
in something close. For example, football knowledge may help but doesn’t carry
over to hockey:

Scientist concedes ‘honest mistake’ about weaponized anthrax – Los Angeles Times

“I believe I made an honest mistake,” Jahrling said in
response to questions e-mailed to him for this article, adding that he had been
“overly impressed” by what he thought he saw under the microscope.

I should never have ventured into this area,” said Jahrling, who is a
virologist, referring to his analysis of the anthrax, which is a
bacterium. Jahrling’s initial analysis — and his briefing of officials at the
White House — was first detailed in a 2002 book by bestselling author Richard
Preston.

Of course, it’s horribly convenient for the FBI. One of
the arguments against Dr. Ivins being the person that sent the anthrax was that
he lacked the skilll to add the silicon. Now the person that made that claim
said he was wrong.