Beware the expert who says he’s an expert at everything.

You bring them in to gain their insight or expertise at one thing.  Next thing you know they are professing that they can handle everything you can throw at them.

These people aren’t experts.  They might think they know everything but no one can be an expert at everything.

I know what I’m an expert at (a couple of things), what I’m good at (a few things), what I know about(lots but that doesn’t make me an expert), and what I’m a novice at (lots here as well). When I know about something and am not an expert or good at it, I give my insight and to push them to someone I trust who is, or help them decide how to find one.   That’s what a real expert does. 

Experts are usually self aware.  They should be able to tell you what they can’t do and what others will do better. 

Experts who profess being able to do anything are self promoters whose personal interests come before yours.

This applies to any field.