Judge high court justice

In 2014, after Michael O’Neill pleaded guilty and was sentenced to 18 years imprisonment for the murder of his partner -- prominent Melbourne interior designer Stuart Rattle -- his lawyers argued that O’Neill’s "dependent personality disorder with prominent features of a narcissistic personality disorder" should lead to a reduction in the sentence because he was suffering a mental impairment. 

The Victorian Court of Appeal disagreed, appearing to say that while mental illness such as depression could lead to a reduction in a person’s sentence if the illness was linked to the offending or would make jail time harsher, personality disorders like O’Neill’s were not to be treated as a mitigating factor.

That is because, as a 2010 Queensland Court of Appeal decision had noted, there was a view that personality disorders “are not illnesses which impact upon the capacity of the sufferer to perceive the world around [them] and respond to it. A personality disorder is a description of a personality type, or the traits which define the person and the person’s predominant modes of behaviour.”