Everyone in the world knows Jennifer Lopez is going to lip synch. It is what she does. I doubt Jennifer has ever actually sang live. I think she probably has a backing track for her shower. Mariah Carey on the other hand can actually sing. She used to be able to sing well. Maybe she can't anymore. I can't think of an explanation where someone who sat a judges table all season and judged people who were not allowed to lip synch, gets up and then lip synchs. There is no explanation. None. She has sung those songs a million times. She has done that same medley a million times. It was supposed to be the ultimate singer showing the American Idol cast how they should sound, but she failed and did so miserably.