Last updated 16 August 2016 This chapter is currently under review.
Under the Criminal Code Act 1899 (Qld) (Criminal Code), a person is not criminally responsible for an act or omission of an act if, at the time of doing the act or making the omission, the person is in such a state of mental disease or natural mental infirmity as to deprive the person of the capacity to:
- understand what they are doing
- control their actions
- know that they ought not do the act or make the omission.
However, a state of mind resulting to any extent from intentional intoxication with alcohol or drugs is excluded.
When the charge is murder, the Criminal Code provides for a partial defence known as diminished responsibility. It refers to an abnormality of mind that has the effect of substantially impairing one or more of the capacities mentioned above.
If diminished responsibility is established, it has the effect of reducing the charge to one of manslaughter.
Questions of unsoundness of mind and diminished responsibility are traditionally decided by a jury in a criminal trial. Juries may also be called upon to decide whether an accused person is not of sound mind at the time of trial or is incapable of understanding the proceedings at trial. Juries have exercised these functions less frequently because the Mental Health Court is now able to decide questions of unsoundness of mind, diminished responsibility and fitness for trial.