Crimes Act 1900

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—

understand the nature of the charge; or

enter a plea to the charge and exercise the right to challenge jurors or the jury; or

understand that the proceeding is an inquiry about whether the person committed the offence; or

follow the course of the proceeding; or

understand the substantial effect of any evidence that may be given in support of the prosecution; or

give instructions to the person’s lawyer.

A person is not unfit to plead only because the person is suffering from memory loss.