(1) A person is presumed to be fit to plead.
(2) The presumption is rebutted only if it is established, on an investigation under this division, that the person is unfit to plead.
(3) The question of a person's fitness to plead—
(a) is a question of fact; and
(b) is to be decided on the balance of probabilities.
(4) No party bears a burden of proof in relation to the question.