잘리가 (or 잘 리가 to be precise) is normally not used by itself. It is probably an elided form of 잘리가 있어? (question) or 잘리가 없어 (negative statement). 잘 리가 없다 = 잘(from 자다, to sleep) + 리(way, sense, truth)가 없다 (there is not). => There is no way that he's sleeping = He can't be sleeping. (a strong speculation) This -ㄹ 리가 없다 is a set structure for "can't be" or "there is no way". For example, - 톰이 안 온다고? 그럴 리가 없어. = Tom's not coming? That can't be true. - 경찰이 그런 걸 모를 리가 있어요? = Can a police officer not know such a thing? (i.e. it's improbable) Sometimes people drop the last part (없어요, dlT어요?) and just say 날리가 or 그럴 리가, because the meaning is still clear while at the same time having the benefit of sounding more dramatic, as if reciting what goes on in their head.