It depends on the society. In Western society at this time in history, a 13 year old is a child. In other societies, now and in the past, a 13 or 14 year old is/was considered an adult....more mature, more responsible and they act it. There is no way that a 13 year old could be considered an adult in Western society. It should not drop below 18 though, as I want 18 year olds held responsible for crimes they commit.