She has to be wearing those earrings. It's not enough that she's looking at him with those eyes, that she's acting less like 'Dr. Temperance Brennan' and more like 'Tempe Brennan.'
One look at those earrings and he's back, back to the voodoo and the blood. Back to that moment when he compromised evidence. For her. Only for her.
When she says I have a way to lodge reasonable doubt in the jury his first thought is I can't talk about this, or I'm going to have to figure out how to stop you.
He knows, though, that he wouldn't.