Last updated 31 January 2018

Criminal responsibility: unsoundness of mind and diminished responsibility 

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, the charge is reduced from murder to manslaughter.

Fitness for trial

Case law has established the minimum standards of understanding that a person must have in order to be able to receive a fair trial, and therefore to be regarded as fit for trial. The Criminal Code recognises this in two provisions—s 613 (Want of understanding of accused person) and s 645 (Accused person insane during trial)—but draws on case law for the interpretation of these sections.

Where can unsoundness of mind, diminished responsibility and fitness for trial be decided?

These issues were traditionally decided by a jury in a criminal trial under the relevant provisions of the Criminal Code. Juries may still be called upon to decide any of these questions. However, the Mental Health Court is also able to decide questions of unsoundness of mind, diminished responsibility and fitness for trial, and many cases in which these issues arise are now diverted from the criminal courts to the Mental Health Court for that purpose.