(1) A person is unfit to stand trial for an offence if, because the person's mental processes are disordered or impaired or for any other reason, the person is (a) unable to understand the nature of the charge; or(b) unable to plead to the charge or to exercise the right of challenge; or(c) unable to understand the nature of the proceedings; or(d) unable to follow the course of the proceedings; or(e) unable to make a defence or answer the charge.(2) Notwithstanding subsection (1)(e) , a person is not unfit to be tried if the only reason that the person is unable to make a defence or answer a charge is that he or she is suffering from memory loss.