What Makes An 'Expert'?

Back in the early 80's, a woman named Patricia Pulling became an 'expert' in the occult after he son committed suicide and she blamed it on D&D.  She gave talks to police agencies, published books, the works.  She also was completely nuts and made up most of her 'facts'. 

That's the first thing I thought of when I read this article on AR-15's w/ an interview by 'Local Terrorism Expert' Edward Bridgeman, an Assoc. Prof. at the Univ. of Cincinnati.

Bridgeman says the AR-15 is the type of weapon that can do the most damage and be purchased legally in the U.S....
The AR-15 is known for its destruction, not accuracy, Bridgeman said.
"It's not a good sniper weapon but good for laying down a lot of fire down range," Bridgeman said.

If he's got this little knowledge (or bias) on one of the most common firearms in the US, in my mind it puts into question his other bonifides as well. Is he just this blind on AR's or is he incompetent in other areas as well?

So what makes an 'expert' beyond the ability to get themselves in front a camera or reporter?