(1) A person is unfit to plead to a charge if the person's mental processes are disordered or impaired to the extent that the person cannot—
(a) understand the nature of the charge; or
(b) enter a plea to the charge and exercise the right to challenge jurors or the jury; or
(c) understand that the proceeding is an inquiry about whether the person committed the offence; or
(d) follow the course of the proceeding; or
(e) understand the substantial effect of any evidence that may be given in support of the prosecution; or
(f) give instructions to the person's lawyer.
(2) A person is not unfit to plead only because the person is suffering from memory loss.