Brennan turns to Booth, ignoring Ms Echolls for the moment.

"Is that the sort of evasiveness that's usually indicative of guilt?"

If it sounds like an honest question, that's because it is one. For quite some time now, Brennan has been observing Booth and how he deals with people. How he can determine so easily if they're lying or what their motivations are.

She's started to pick up a little bit, and is curious to know if her instincts are correct.