It is presumed--
(a) that a person who has, in accordance with this Part or on a review under Part 5, been found to be unfit to be tried for an offence continues to be unfit to be tried for the offence until the contrary is, on the balance of probabilities, determined to be the case, and
(b) that a person who has, in accordance with this Part or on a review under Part 5, been found fit to be tried for an offence continues to be fit to be tried for the offence until the contrary is, on the balance of probabilities, determined to be the case.