Answer:
Juries
With the except of the US Supreme Court, appellate courts also lack original (trial) jurisdiction over cases. They typically review cases using panels of three judges, although some cases are heard by a single judge, and others by the full court (en banc).
Because the US Supreme Court has original jurisdiction over a small class of cases (although it currently only hears disputes between the states), original jurisdiction doesn't work as the answer to this question.