What's so surprising in that? FBI can probably hire an expert in any existing technology. I'm sure they have very smart people working for them, and if they need they can always use outside consultants. I'd be pretty surprised and disappointed if they didn't have some experts with knowledge in everything that pertains to internet security, cracking, etc. There's a whole industry about that, for years now, so why not?
I guess what I'm saying is, it makes it sound like they have a guy on staff (not contracted) whose whole job is to be the TOR expert. I just wasn't expecting TOR would be that important.
It doesn't say his whole job is to be TOR expert. He could have knowledge in TOR - one doesn't have to be exceptionally knowledgeable to be considered "expert" in legalese, regular working knowledge of the matter allowing him to make informed conclusions like "this set of packets is a TOR traffic going to this IP" should be enough - and other matters too.
