If he does not sense evil on Sasuke then it's because he's good.
It's the same ability of Mito-sama, and it's explained he said that "she could sense evil".
He never said that he could "scan" the people's hearts to know if they are feeling love, fondness or whatever which is what you are implying, the thuth is he can only sense evil and this is said explicity when Obito brought up the "Mito-sama" stuff when he said that it was the same ability.

How come you always take what people say so literally? You reply to a post, and bold out one sentence instead of looking at the bigger picture, and if you read something you don't like you may as well stop reading halfway.
I don't think he can sense people's emotions, in fact I said the opposite. He can not read people's minds, or feel their feelings. He can only sense brightness(I think so because Karin sensed his light, it would be illogical if he could only sense the negative) and darkness within people's hearts.
What I meant by scanning people is that I hope he doesn't use this ability as a mental byakugan to detect evil and fight it that way. It's a jutsu, way too easy.
Edited by sushi., 22 January 2013 - 04:07 PM.